Table of Content

12 August 2023, Volume 49 Issue 8

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CROP GENETICS & BREEDING · GERMPLASM RESOURCES · MOLECULAR GENETICS

Identification of OsGMS2 and construction of seed production system for genic male sterile line in rice

TANG Jie, LONG Tuan, WU Chun-Yu, LI Xin-Peng, ZENG Xiang, WU Yong-Zhong, HUANG Pei-Jin

Acta Agronomica Sinica. 2023, 49(8):  2025-2038.  doi:10.3724/SP.J.1006.2023.22051

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Male sterility is the basis for application of crop heterosis. The common nuclear male sterile mutant osgms2 was isolated from a mutant library created by ⁶⁰Co-γ-treated indica cultivar 93-11. The male of the mutant was completely aborted, the female was nomal, and other agronomic characters were consistent with those of the wild type. Genetic analyses indicated that the male sterility phenotype was stably controlled by a single recessive gene. The OsGMS2 gene was fine-mapped within the 86 kb physical interval between two molecular markers S3b and 4826 on the long arm of chromosome 4 with a mapping population of osgms2 and Minghui 63. Further sequencing found the gene LOC_Os04g48490, encoding a fasciclin-like arabinogalactan protein, had a 9-bp deletion at position 118 to 126 from start codon of translation, resulting in three codons mutation. The osgms2 gene was a novel allele of OsFLA1. Subsequent gene knockout and genetic complementation experiments in Zhonghua 11 background confirmed the function of the gene. Real-time quantitative PCR (qPCR) analyses showed that the gene was expressed in all tissues, with the highest level at the flowering and immature seed stages. Alignment analyses revealed that the protein sequence was conserved in different species. By creating the OsGMS2-T maintainer, seed production of the common sterile line was achieved. The identification of the allelic mutant osgms2 provides the new materials for the study on rice nuclear male sterility and application of heterosis.

Indica-japonica attribute identification and heterosis utilization of diploid rice lines reverted from tetraploid rice

SONG Zhao-Jian, FENG Zi-Yi, QU Tian-Ge, LYU Pin-Cang, YANG Xiao-Lu, ZHAN Ming-Yue, ZHANG Xian-Hua, HE Yu-Chi, LIU Yu-Hua, CAI De-Tian

Acta Agronomica Sinica. 2023, 49(8):  2039-2050.  doi:10.3724/SP.J.1006.2023.22057

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In this study, the indica-japonica attribute of eight reverted diploid lines were identified by InDel molecular marker. The hybrid combinations were made between the reverted diploid lines and photoperiod- and thermo-sensitive genic male sterile lines Peiai 64S (indica) and Nongken 58S (japonica), respectively. The genetic distance and cluster analysis of the parents and hybrids were carried out, the yield related traits of the hybrids and the male parents were investigated, then the over male parent heterosis and the competitive heterosis of the hybrids were analyzed. In addition, the correlation between parental genetic distance and the heterosis was analyzed to explore the feasibility of using parental genetic distance to predict heterosis. The results showed as follows: (1) The indica gene frequency of the reverted diploid lines ranged from 0.605 to 0.947. All lines had both indica and japonica genetic components, but the proportions of indica and japonica components were different from each other. (2) The genetic distance between the reverted diploid lines and Pei’ai 64S were 0.21-0.42, and that between the reverted diploid lines and Nongken 58S were 0.68-0.95. The materials with the same or similar indica-japonica attribute were clustered together, which clearly showed the genetic relationship between the materials. (3) The heterosis utilization of the reverted diploid lines needed the participation of wide compatibility genes. The hybrid combinations made between Peiai 64S that had wide compatibility gene and the reverted diploid lines had obvious over male parent heterosis and competitive heterosis in the effective panicle number per plant, the total grain number per panicle, and the filled grain number per panicle. In the yield per plant, eight hybrid combinations all showed over male parent heterosis and competitive heterosis, especially the yield per plant of HYP2 was prominent, up to 45.92%. (4) The genetic distance of parents was significantly positively correlated with the total grain number per panicle and the yield per plant of the hybrids, indicating that the InDel genetic distance can be used for predicting heterosis. The study confirmed that the reverted diploid lines from the tetraploid indica-japonica subspecies rice had both indica and japonica genetic components, and contained abundant genetic diversity. Using the reverted diploid lines, the hybrid combinations with super heterosis could be made, which providing a theoretical basis and reference for the utilization of indica-japonica subspecies heterosis through the combination of indica-japonica intermediate lines and photoperiod- and thermo-sensitive genic male sterile lines with wide compatibility genes. At the same time, we preliminarily confirmed the feasibility of the pathway “breeding new diploid rice varieties by using polyploid as the vector for creating variation”, which provided a new idea and approach for rice breeding.

Haplotype analysis of soybean leaf type regulator gene Ln and its homologous genes

LI Gang, ZHOU Yan-Chen, XIONG Ya-Jun, CHEN Yi-Jie, GUO Qing-Yuan, GAO Jie, SONG Jian, WANG Jun, LI Ying-Hui, QIU Li-Juan

Acta Agronomica Sinica. 2023, 49(8):  2051-2063.  doi:10.3724/SP.J.1006.2023.24208

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Soybean leaf type is an important component of ideal plant type, which is of great significance for the breeding of soybean varieties. In this study, we analyzed the haplotype of Ln and its homologous gene (Glyma.10G273800) in 598 materials from different regions of China. Ln gene and homologous gene contained three haplotypes (Hap1-Hap3), respectively. There was no significant difference in leaf length between the three haplotypes of Ln gene, and Hap2 was significantly different from Hap1/Hap3 in leaf width, leaf area, and leaf length width ratio. There were significant differences between Hap3 and Hap2 of Ln homologous gene in different leaf types. There was no difference in the ratio of leaf length to width between Hap1 and Hap2. There was no significant difference in leaf width phenotype at the 4th leaf site, and Hap1 at the 5th leaf site was significantly lower than Hap2. Leaf length, leaf area, and leaf circumference Hap1 were significantly lower than Hap2. In terms of geographical distribution, Hap2 of Ln gene was mainly distributed in high latitude and high altitude regions, and no obvious regional bias was detected in the distribution of the three haplotypes of its homologous genes. Genetic analysis showed that only D9H of Hap2 in Ln gene had artificial selection signal, while the other two mutation sites in Ln gene and two mutation sites in homologous gene had no artificial selection signal. This study provides the theoretical basis for soybean leaf type breeding and has positive significance for increasing soybean yield.

A retrospective analysis of the historical evolution and developing trend of maize mega varieties in China from 1982 to 2020

BAI Yan, GAO Ting-Ting, LU Shi, ZHENG Shu-Bo, LU Ming

Acta Agronomica Sinica. 2023, 49(8):  2064-2076.  doi:10.3724/SP.J.1006.2023.23067

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Seed is the chip of agriculture and the upgrading of excellent varieties has played an important role in improving the yield of corn in China. It is of great practical significance to study the historical contribution and developing trend of mega maize varieties in China in recent 40 years. Based on the dataset of planting area of individual maize varieties released by the National Extension and Service Center of Agricultural Technology from 1982 to 2020, 27 mega maize varieties such as Zhengdan 958 in recent 40 years with the total promotion of 321 million hectares accounting for 29.09% of the total corn planting area in China were screened..There were four utmost mega varieties (Zhengdan 958, Zhongdan 2, Danyu 13, and Xianyu 335) and six massive mega varieties (Jundan 20, Yedan 2, Nongda 108, Yedan 13, Sidan 19, and Yandan 14). The promotion period was 8-30 years, with an average of 17.63 years, the maximum promotion area in a single year was 699,700-4,569,500 hm², with an average of 1,507,900 hm². It was mainly distributed in Shandong, Henan, Hebei, Jilin, Heilongjiang, Inner Mongolia, and other production regions and the provinces (regions) with 13 varieties exceeding 666,700 hm² per year were Shandong, Henan, Hebei, Jilin, Heilongjiang, Inner Mongolia, Liaoning, and Sichuan. The proportion of planting area of mega varieties to the total area increased rapidly from 1982 to 1989, remained stable from 1990 to 1997, decreased after 1998, and decreased to about 12% by 2020. Some varieties such as Yufeng 303 and Zhongkeyu 505 had the potential to develop into mega varieties. In the future, intelligent design breeding will efficiently cultivate a new generation of breakthrough varieties and accelerate the improvement of maize yield. According to the current maize production problems and future development trends, it is recommended to further improve the regional test of maize varieties in terms of distribution layout, test accuracy and variety approval standards of regional tests.

Identification and gene localization of a novel maize nuclear male sterility mutant ms6

WANG Xing-Rong, ZHANG Yan-Jun, TU Qi-Qi, GONG Dian-Ming, QIU Fa-Zhan

Acta Agronomica Sinica. 2023, 49(8):  2077-2087.  doi:10.3724/SP.J.1006.2023.23062

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The localization, cloning, and functional mechanism research of male sterility genes can not only deepen our understanding of the molecular regulation mechanism of male flower growth and development, but also effectively promote the development of male sterility technology system and its application in maize breeding and seed production in maize. In this study, maize inbred line Mo17 was used as the wild-type background material, and a maize male sterile mutant, named male sterile 6 (ms6), was obtained by EMS mutagenesis. Phenotypic identification of ms6 mutant plants showed that they could perform normal tasseling, but the male flower glume could not dehiscence and powder could not disperse normally, and the pollen grains were dry, indicating pollen free sterility. Meanwhile, there were no significant differences between ms6 and Mo17 wild type (WT) in plant architecture, ear-related traits, kernel size, and other related traits, demonstrating that the ms6 gene only affected plant fertility, but did not affect other agronomic traits. Cytological observation revealed that the microspore of ms6 mutant was abnormal at the late stage of microspore development, which showed that tapetal cells were degenerated in advance, and the microspore could not undergo mitosis and gradually split. Scanning electron microscopy demonstrated that the anther epidermis of mutant ms6 were shrunk, and there was no intact pollen or ubisch on the inner surface of anther locule. Genetic analysis revealed that the ms6 phenotype was controlled by a pair of recessive nuclear genes. Combined with phenotypic and genotypic linkage analysis, ms6 was initially located between C6-19 and C6-30 on maize chromosome 6 by using the ms6 × B73 F₂ genetic mapping population and about 200 pairs of polymorphic SSR markers in the whole genome, and 10 pairs of newly developed polymorphic markers in the interval were further used. Finally, ms6 was located within the interval of about 480 kb between M13-M14. Gene mapping located the mutation site into a 480 kb interval between M13 and M14. Zm00001d035201 was preliminarily identified as the key candidate gene of ms6 by RNA-Seq combined with qRT-PCR. Zm00001d035201 encoded an acid ribosomal protein. This study provides a solid foundation for further studies on the function of ms6 gene. Meanwhile, as a novel male sterile mutant, ms6 also provides the important material support for the production and application of new maize genetic sterile genes in the future.

Characterization and genetic analysis of a new allelic mutant of Miniature1 gene in maize

WANG Juan, XU Xiang-Bo, ZHANG Mao-Lin, LIU Tie-Shan, XU Qian, DONG Rui, LIU Chun-Xiao, GUAN Hai-Ying, LIU Qiang, WANG Li-Ming, HE Chun-Mei

Acta Agronomica Sinica. 2023, 49(8):  2088-2096.  doi:10.3724/SP.J.1006.2023.23059

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Grain development is a key determinant for maize grain yield and quality, but the regulatory mechanisms have not been fully revealed. A maize mutant deficient in kernel development was found and selected in our field. The mutant exhibited an incomplete grain filling, reduced embryo and endosperm size, and shriveled mature grains and empty pericarp. Genetic analysis suggested that the mutant phenotype was controlled by a single recessive nuclear gene. The candidate gene was preliminarily mapped to a 1.1 Mb interval on chromosome 2, and further a hAT transposon was inserted into the first exon of Miniature1 (Mn1) gene, which resulting in a frame-shift mutation and down-regulated expression of Mn1. The transposon insertion was fully linked to the defective kernel phenotype of the mutant, which was nominated as mn1-m2. Allelism test of mn1-m2 and mn1-89 suggested that mn1-m2 was a noval allelic mutant of Mn1 gene. In conclusion, we identified a new allelic mutant of Mn1 gene with different mutation site and type, which improved maize germplasm resources and provided new genetic materials for the analysis of the mechanism of Mn1 regulation on kernel development.

Identification of major QTLs for nodule formation in peanut

HUANG Li, CHEN Wei-Gang, LI Wei-Tao, YU Bo-Lun, GUO Jian-Bin, ZHOU Xiao-Jing, LUO Huai-Yong, LIU Nian, LEI Yong, LIAO Bo-Shou, JIANG Hui-Fang

Acta Agronomica Sinica. 2023, 49(8):  2097-2104.  doi:10.3724/SP.J.1006.2023.24184

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Peanut is an important oil and economic crop of legumes in China. Nodules are important for symbiotic nitrogen fixation in peanut. Dissecting the genetic basis of nodule formation could promote the understanding of nitrogen fixation ability and characteristics of nodules in peanut. However, there are few studies on nodule formation and the genetic basis of nodule formation remained unclear in peanut. In this study, the nodules were investigated in a high generation RIL population and seven lines were identified without nodule. The chlorophyll content, plant height, fresh weight per plant, and dry weight per plant of the lines without nodule were significantly lower than those of parents. Using the previous genetic linkage map based on SSR markers, major QTLs qPNA08 and qPNB07 were identified on chromosome A08 and B07, respectively. The InDel markers in the two major QTLs were developed by the genome resequencing data of parents and performed amplification in the RILs. The interval of QTLs qPNA08 and qPNB07 was reduced to 1.6 Mb and 1.8 Mb, respectively. Meanwhile, the phenotypic variation explained of these two QTLs was increased to 16.4% and 9.9%, respectively. There were four and two nodulin genes variation loci in the two target intervals, respectively. This study provided the understanding for unveiling the genetic basis of formation and development of nodule and symbiotic nitrogen fixation in peanut.

Genome-wide identification of the HAK/KUP/KT potassium transporter family in foxtail millet and its response to K⁺ deficiency and high salt stress

DAI Shu-Tao, ZHU Can-Can, MA Xiao-Qian, QIN Na, SONG Ying-Hui, WEI Xin, WANG Chun-Yi, LI Jun-Xia

Acta Agronomica Sinica. 2023, 49(8):  2105-2121.  doi:10.3724/SP.J.1006.2023.24194

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KT/HAK/KUP (HAK) family is the most abundant potassium (K⁺) transporter family in plants, which plays important roles in plant growth and environmental adaptation. Foxtail millet (Setaria italic L. Beauv) is a model plant for studies on stress resistance mechanisms. However, the HAK family has not yet been well characterized in foxtail millet. In this study, 29 Setaria italic HAK genes (SiHAKs) were identified based on genome-wide sequence information, and the basic characteristics, protein structure, chromosome location, gene replication, expression pattern, and responses to stress were comprehensively analyzed. The results showed as followes: (1) SiHAKs were divided into five phylogenetic clusters (Cluster I-Cluster V), containing 11, 9, 3, 3 and 3 members, respectively. Gene structure and conserved motif analyses indicated that SiHAKs was high conserved, and the conservatisms were as follows: Cluster III = Cluster V > Cluster II > Cluster I > Cluster IV. (2) Tandem replication was the main contribution to the amplification of SiHAKs. 15 SiHAKs were located in tandem replication. (3) 171 transcription factors, including a large number of members of ERF, NAC, MYB and WRKY families, may bind to the promoter sequences of SiHAKs, which may confer SiHAKs diverse response mechanisms to abiotic stress. (4) SiHAKs were divided into three groups (Group I, Group II, and Group III) by gene expression Cluster Ing. The relative expression patterns of most SiHAKs were consistent in the two varieties (Zhanggu and Yugu 1). The relative expression levels of SiHAKs from the five clusters were generally as follows: Cluster III > Cluster V > Cluster II > Cluster I> Cluster IV. (5) Eleven SiHAKs with high expression levels in root were selected to detect the responses to low K⁺ and high salt stress. Under K⁺ deficiency treatment, eight SiHAKs were markedly upregulated in the expression levels, one SiHAK was significantly decreased, and two SiHAKs had no obvious changes. Under high salt stress, Three SiHAKs were significantly increased in the expression levels, two SiHAKs were significantly decreased, and the remaining six SiHAKs had no obvious changes. Remarkably, SiHAK15 had the strongest response to K⁺ deficiency and high salt stress, its expression level was 151 times and 22 times of the control, respectively. (6) The differences of gene expression profiles reflected the function differences among SiHAKs from different clusters. SiHAKs from Cluster I were mainly expressed in root, implying their important roles in K⁺ absorption in root. SiHAKs from Cluster II generally had no tissue-specific expression characteristics, and might be involved in many biological processes, such as K⁺ absorption and transport, plant growth and development. SiHAKs from Cluster III were upregulated by K⁺ deficiency and high salt stress, inferring their potential roles in maintaining K⁺/Na⁺ balance and resisting salt stress. SiHAKs from Cluster IV were almost undetectable in gene expression in the tested tissues. SiHAKs from Cluster V had different responses to K⁺ deficiency and high salt stresses. Some of them were upregulated in gene expression, while others were inhibited, thus indicating that the members from Cluster V were functionally differentiated. This results not only provide the foundation for further functional studies of SiHAKs, but also provide the valuable guidance for the study of K⁺ efficient utilization and salt tolerance mechanism in plants.

Differences of physiological responses and transcriptional regulation of alfalfa with different drought tolerances under drought stresses

CHEN Li, WANG Jing, QIU Xiao, SUN Hai-Lian, ZHANG Wen-Hao, WANG Tian-Zuo

Acta Agronomica Sinica. 2023, 49(8):  2122-2132.  doi:10.3724/SP.J.1006.2023.24205

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Alfalfa is the most important legume forage, which is often planted in aird or semi-arid regions. The objective of this study is to explore the responsive mechanism of alfalfa with different drought tolerance to drought stress, which provides the theoretical basis for tolerant breeding of alfalfa. In this study, the new variety Medicago sativa ‘Zhongke 1’ was used as the test material, and M. sativa ‘Sanditi’ was used as the control. The effects of drought stress on growth traits, photosynthesis, chlorophyll concentration, leaf water content, osmotic adjustment substances, and antioxidant enzyme activities were determined by natural drought strategy in pots. The deferentially expressed genes were compared by transcriptome analysis. Drought stress significantly reduced plant height, biomass, relative water content of leaves, photosynthetic rate, transpiration rate, stomatal conductance, intercellular carbon dioxide and chlorophyll concentration of alfalfa. Compared with Sanditi, Zhongke 1 revealed the lower malondialdehyde concentration and electrical conductivity under drought stress, but stronger osmotic regulation ability and superoxide radical scavenging ability. Transcriptome sequencing identified 5308 and 8053 drought-responsive genes of Zhongke 1 and Sanditi, respectively. GO functional annotation demonstrated that 346 drought-responsive genes were significantly enriched in six GO item categories in Zhongke 1, while 1683 drought-responsive genes in Sanditi were significantly enriched in 29 GO item categories. The relative expression levels of 19 key drought-tolerant genes in Zhongke 1 were significantly higher than those in Sanditi. Alfalfa may maintain a relatively high photosynthetic rate by up-regulating the relative expression levels of drought tolerant genes SUS, P5CS, LEA, SOD, POD, PEPC, and NCED, thus improving osmotic regulation ability and antioxidant enzyme activity. The results provide a theoretical basis for further exploration of alfalfa’s candidate genes in response to drought stress and drought tolerant breeding.

Identification of wheat dwarf mutant Xu1801 and analysis of its dwarfing effect

SU Zai-Xing, HUANG Zhong-Qin, GAO Run-Fei, ZHU Xue-Cheng, WANG Bo, CHANG Yong, LI Xiao-Shan, DING Zhen-Qian, YI Yuan

Acta Agronomica Sinica. 2023, 49(8):  2133-2143.  doi:10.3724/SP.J.1006.2023.21056

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A natural dwarf mutant was discovered in the purification and rejuvenation of Xumai35 (XM35) foundation seeds. After multiple generations of individual selection, the dwarf trait of the mutant named Xu1801 temporarily could be stably inherited. To explore the cause of dwarfing phenotype, agronomic traits, lodging index analysis, gibberellin treatment at seedling stage, and dwarf-related genes detection were carried out. The results showed that the average plant height was 68.16 cm in Xu1801, shorter by24.05% than the wild-type XM35. The dwarfing effect of Xu1801 was manifested in the reduction of internode number and the extremely significant shortening of internode length. Among all internodes, the 5th internode had the largest dwarfing effect (44.16%). Flag leaf width, chlorophyll content, and spikelet density were extremely significantly higher in Xu1801 compared with XM35, and there was no difference in other agronomic traits. Compared with XM35, the grain yield of Xu1801 was lower by 8604.17 kg hm^-2, while protein content, wet gluten content, and sedimentation volume of Xu1801 were significantly improved. The stem of Xu1801 was thick, and the internode fullness was extremely significantly higher than that of XM35. The lodging index was 47.73, extremely significantly lower than that of XM35, indicating its outstanding lodging-resistance ability. The detection of dwarfing gene-linked molecular markers revealed that Xu1801 might contain Rht-D1b, Rht4, Rht8, Rht9, and Rht12. Except for WMC317 (Rht4) and BARC102 (Rht5) revealed different amplification bands between Xu1801 and XM35, the amplification bands of other markers were relatively consistent. In conclusion, Xu1801 not only had short plant height and excellent lodging resistance, but also coordinated grain yield and quality characteristics properly, demonstrating the outstanding potential for cultivation. Meanwhile, Xu1801 carried several dwarfing genes and could be utilized as germplasm resources for genetic analysis of wheat plant height.

Development of high-quality fragrant indica CMS line by editing Badh2 gene using CRISPR-Cas9 technology in rice (Oryza sativa L.)

WEI Xin-Yu, ZENG Yue-Hui, YANG Wang-Xing, XIAO Chang-Chun, HOU Xin-Po, HUANG Jian-Hong, ZOU Wen-Guang, XU Xu-Ming

Acta Agronomica Sinica. 2023, 49(8):  2144-2159.  doi:10.3724/SP.J.1006.2023.22043

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Fragrance is one of the important traits for quality improvement in rice, which is mainly controlled by the Badh2 gene encoding a betaine aldehyde dehydrogenase on chromosome 8. The mutation of Badh2 gene can increase the content of 2-acetyl-1-pyrroline (2-AP) and promote the fragrance production in rice. In this study, the Badh2 gene in Mingtai B (MTB), an elite maintainer line of Indica hybrid rice showing high eating quality bred by Sanming Academy of Agricultural Sciences, was edited and knocked out by using CRISPR-Cas9 technology. Two T₀ transgenic lines carrying homozygous mutation on the loci of Badh2 were generated, and 48 T₁ individuals derived from these two plants were genotyped by PCR amplification and sequencing analysis. A mutant line named MTB-badh2, which had a single T nucleotide insertion in the second exon of Badh2 without the vector skeleton, was finally obtained. In our study, the expression of Badh2 and the content of 2-AP were determined by semi-quantitative RT-PCR, qRT-PCR, and gas chromatography-mass spectrometry (GC-MS), respectively. Simultaneously, the 48 pairs of SSR markers recommended by “Sector Standard of Agriculture (NY/T 1433-2014)” were used to further analyze the DNA fingerprint and genetic diversity of the MTB and the MTB-badh2. The results showed that the Badh2 RNA level was significantly decreased in the MTB-badh2 compared with the wild-type MTB. In addition, the 2-AP content was dramatically increased in MTB-badh2. DNA fingerprint analysis revealed that only the Rm571 primer pair was specific for identifying allelic variation between wild type and MTB-badh2, suggesting that the genetic diversity between wild type and MTB-badh2 was very low. Furthermore, agronomic phenotype, cooking and eating quality, appearance quality of wild type, and MTB-badh2 were investigated and analyzed. There was no significant difference between MTB and MTB-badh2. The corresponding stable fragrant CMS line Mingtai A-badh2 (MTA-badh2) carrying homozygous mutant on the locus of Badh2 was successfully generated by the conventional test-crossing and back-crossing techniques combined with Badh2 sequencing analysis. Derived from this CMS line, MTA-badh2/Minghui 1831, MTA-badh2/Minghui 703, and MTA-badh2/Minghui 3009 hybrid combinations had been bred. Among them, the grain yield of MTA-badh2/Minghui 703 and MTA-badh2/Minghui 3009 were significantly increased compared with that of Mingtai you 703 and Mingtai you 3009, which were registered and released by the National Crop variety Appraisal Committee. Moreover, MTA-badh2/Minghui 1831 dramatically increased 2-AP content in the grains compared with MTA/Minghui 1831. Therefore, the CRISPR-Cas9-mediated technology could be used to edit the Badh2 and improve the fragrance in rice, and it provides the theoretical guidance for development of fragrant indica CMS line, leading to an accelerated breeding process of fragrant hybrid rice.

QTLs mapping for single-seed weight of cultivated peanut

LI Xing, YANG Hui, LUO Lu, LI Hua-Dong, ZHANG Kun, ZHANG Xiu-Rong, LI Yu-Ying, YU Hai-Yang, WANG Tian-Yu, LIU Jia-Qi, WANG Yao, LIU Feng-Zhen, WAN Yong-Shan

Acta Agronomica Sinica. 2023, 49(8):  2160-2170.  doi:10.3724/SP.J.1006.2023.24190

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Peanut (Arachis hypogaea L.) is an important oil and cash crop in China, and the single-seed weight is one of the important traits that determine the yield and commodity of peanut. In this study, QTLs mapping for single-seed weight of peanut was performed using RIL population constructed from a cross between large-kernel variety Shanhua 15 (female) and small-kernel variety Zhonghua 12 (male), based on a high-density genetic map. Nine QTLs related to single-seed weight were identified on seven chromosomes (A04, A06, A07, B05, B07, B09, and B10). The LOD values of these QTLs was 3.01-33.97, phenotypic variation contribution rates was 2.61%-34.28%, the additive effect values were -0.03 to 0.15 g, and the physical range of positioning was 0.03-4.32 Mb. qSSWA07.1 was a stable major QTL repeatedly detected in six planting environments, and qSSWA06.1 and qSSWB09.1 were repeatedly detected in four planting environments. The additive effect of qSSWA07.1 and qSSWA06.1 were positive, and the favorable alleles were inherited from Shanhua 15. The additive effect of qSSWB09.1 was negative, and the favorable allele was inherited from Zhonghua 12. The additive effect of qSSWA06.1, qSSWA07.1, and qSSWB09.1 on peanut single-seed weight was analyzed with the genotype of three bin markers (A06: Block3344, A07: Block3373, and B09: Block10032) closely-linked with QTLs. The mean value of single-seed weight of lines with three favorable alleles was the largest, and that of the lines without the favorable alleles was the smallest. The candidate genes in qSSWA06.1, qSSWA07.1, and qSSWB09.1 were analyzed by KEGG enrichment pathway, according to the expression in different tissues and functional annotation of these genes, four candidate genes were predicted, Arahy.9UY90I, Arahy.RX7YKY, Arahy.3ZC2CN, and Arahy.9V2WXE, which may play a significant role in the regulation of peanut seed growth and development. The results provided the reference for the genetic improvement of yield related traits in peanut.

Expression and functional characterization of NtNAC080 transcription factor gene from Nicotiana tabacumin under abiotic stress

WEN Li-Chao, XIONG Tao, DENG Zhi-Chao, LIU Tao, GUO Cun, LI Wei, GUO Yong-Feng

Acta Agronomica Sinica. 2023, 49(8):  2171-2182.  doi:10.3724/SP.J.1006.2023.24193

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NAC proteins, which constitute one of the largest plant-specific transcription factor families, are widely involved in the regulation of plant development, senescence and stress responses. To explore the function of NtNAC080 in abiotic stress response, qRT-PCR was used to analyze the relative expression pattern of NtNAC080 genes under different abiotic stress treatments. Results showed that the relative expression level of NtNAC080 genes was induced by drought, salt, ABA, MeJA, and SA treatments. The NtNAC080 mutant and WT (K326) plants were used to analyze the phenotypes under salt and drought stresses. Results showed that NtNAC080 knockout tobacco lines had increased tolerance to salt and drought stresses. Under salt and drought stresses treatments, the antioxidant enzymes (SOD, POD, and CAT) activities, soluble protein, and proline contents of these two knockout lines plants were significantly higher than those of WT, while MDA content was significantly lower than that of WT. In contrast, NtNAC080-overexpressing Arabidopsis plants had more sensitive to salt and drought stresses. Furthermore, NtNAC080 mutation in tobacco resulted in the up-regulated expression of abiotic stress-related genes (NtDREB1A, NtKAT2, and NtNHX1) after salt and drought treatments. These results indicated that NtNAC080 could be play a negative role in response to salt and drought stresses by regulating the activity of antioxidant enzymes and the relative expression level of stress-related genes.

TILLAGE & CULTIVATION · PHYSIOLOGY & BIOCHEMISTRY

Responses of photosynthetic physiological characteristics of maize varieties released in different decades to nitrogen application rate in Jilin province

CAO Yu-Jun, LIU Zhi-Ming, LAN Tian-Jiao, LIU Xiao-Dan, WEI Wen-Wen, YAO Fan-Yun, LYU Yan-Jie, WANG Li-Chun, WANG Yong-Jun

Acta Agronomica Sinica. 2023, 49(8):  2183-2195.  doi:10.3724/SP.J.1006.2023.23058

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It is of great practical significance to clarify the response trend of yield, leaf nitrogen content, and photosynthetic characteristics of maize varieties released in different years in Jilin province to different nitrogen levels for the breeding of high-yield maize varieties in Northeast China. In this study, six representative varieties popularized and applied in Jilin province since 1970s were used as the materials (1970s: JD101, ZD2; 1990s: SD19, JD159; 2010s: XY335, NH101). Field experiments with four nitrogen levels (0, 125, 250, and 375 kg hm^-2) were set up to analyze the effects of nitrogen application on the yield, leaf nitrogen content, and photosynthetic characteristic parameters of maize varieties released in different decades. The results showed that maize grain yield under all nitrogen levels increased with the replacement of varieties, and the yield advantage of modern varieties was more obvious under high nitrogen levels. The increase of grain yield under different treatments was mainly due to the simultaneous increase of kernel numbers per ear and kernel weight. The net photosynthetic rate (P_n) of ear leaf increased with the increase of nitrogen application rate at no more than 250 kg hm^-2, and the P_n of modern varieties was significantly higher than that of old varieties. When the nitrogen application rate was 375 kg hm^-2, P_n decreased significantly, and the degree of reduction showed that the old varieties were higher than the modern varieties. From silking to dough stage, the decrease of P_n decreased with the increase of nitrogen application and varieties evolution. The light compensation point and dark respiration rate of maize were the highest in 2010s, the second in 1990s and the lowest in 1970s at different stages. Compared with 1990s and 1970s, the light compensation point of maize in 2010s increased by 9.72% and 27.84% on average, and the dark respiration rate increased by 7.82% and 32.98% on average. The specific leaf weight (SLW) of varieties increased with the increase of nitrogen application rate, but SLW decreased with the evolution of varieties under the same nitrogen application rate. The leaf nitrogen content per unit area (N_area) of different varieties increased with the increase of nitrogen application rate, but it was significantly decreased in the old cultivars without nitrogen application, and there was no significant difference among the cultivars treated with nitrogen application rate. The correlation analysis showed that there was a significant positive linear correlation between P_n and SLW, and the relationship between P_n and N_area can be fitted by the quadratic equation, the N_area value of P_n turning with the increase of N_area was 1.57 g m^-2. The photosynthetic nitrogen use efficiency (PNUE) of all varieties decreased with the increase of nitrogen application rate, while the PNUE of cultivars at higher nitrogen levels (≥ 250 kg hm^-2) increased significantly with the evolution of varieties. Thus, compared with the old varieties, the modern varieties were more beneficial to yield improvement in the higher nitrogen levels (≥ 250 kg hm^-2), which was mainly attributed to the higher P_n and PNUE of the modern varieties, while the increase of P_n and PNUE was closely related to the specific leaf weight (SLM), leaf N content (N_mass, N_area), and other characters, which was recommended for reference in the breeding process of maize varieties.

Modeling the response of winter wheat to deficit drip irrigation for optimizing irrigation schedule

YANG Xiao-Hui, WANG Bi-Sheng, SUN Xiao-Lu, HOU Jin-Jin, XU Meng-Jie, WANG Zhi-Jun, FANG Quan-Xiao

Acta Agronomica Sinica. 2023, 49(8):  2196-2209.  doi:10.3724/SP.J.1006.2023.21054

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Combining drip irrigation and water-saving irrigation can increase crop use efficiency greatly, however, few studies investigated water-saving irrigation schedule for winter wheat under drip irrigation conditions. Using crop models to optimize water-saving irrigation systems can make up for the shortcomings of field trials, which can provide the guideline for precise irrigation. In this study, we evaluated the adaptability of the Root Zone Water Quality Model and Crop Estimation through Resource and Environment Synthesis (RZWQM-CERES) using the data from a three-year experiment with drip irrigation water conservation for winter wheat at Jiaodong area. Then we evaluated the influences of different water-saving drip irrigation schedules on winter wheat yield and water use efficiency. The results showed that RZWQM-CERES could effectively simulate the responses of soil moisture, winter wheat growth, and yield to different irrigation treatments and seasons. Root mean square error (RMSE), relative root mean square error (NRMSE), and coefficient of determination (R²) for the simulated soil water storage in 0-90 cm layer were 22.7-32.3 mm, 11.9%-16.3%, and 0.52-0.69, respectively. RMSE, NRMSE, and R² values for simulated harvest above-ground biomass were 1184-1904 kg hm^-2, 9.9%-16.8%, and 0.67, respectively. The corresponding values for simulated grain yield were 361-491 kg hm^-2, 5.7%-7.8%, and 0.75, respectively. The long-term simulation results revealed that the critical water requirement period of winter wheat in this region was the booting period (in wet years and normal years) or the jointing period (in dry years). According to the different responses of winter wheat yield and water use efficiency to irrigation amounts and timings among the different rainfall patterns, the recommended optimal drip irrigation regimes for winter wheat at this region were 45 mm irrigation at both jointing and flowering stages in wet years, and 35 mm (or 45 mm) irrigations at the jointing, booting, and flowering stages in normal years (or dry years). These simulation results extended RZWQM-CERES to optimize drip irrigation schedule of winter wheat and provided an important technical support for the implementation of precise irrigation for winter wheat in the region.

Effects of exogenous trehalose on physiological characteristics and yield of wheat flag leaves under high temperature stress at grain filling stage

LI Yu-Xing, MA Liang-Liang, ZHANG Yue, QIN Bo-Ya, ZHANG Wen-Jing, MA Shang-Yu, HUANG Zheng-Lai, FAN Yong-Hui

Acta Agronomica Sinica. 2023, 49(8):  2210-2224.  doi:10.3724/SP.J.1006.2023.21057

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In order to investigate the effect of exogenous trehalose (TRE) on the physiological characteristics and yield of flag leaves of wheat varieties with different tolerance under high temperature stress during grain filling period, the experiments were conducted in the high-tech agricultural park of Anhui Agricultural University from 2020 to 2022. The sensitive wheat varieties Fanmai 5 (FM5) and heat-resistant wheat varieties Huaimai 33 (HM33) with significant difference in heat resistance were selected as the experimental materials, there were five treatments of spraying water + non high temperature (CK1), water + high temperature stress (CK2), 10 mmol L^-1 trehalose + high temperature stress (T₁₀H), 15 mmol L^-1 trehalose + high temperature stress (T₁₅H), and 20 mmol L^-1 trehalose + high temperature stress (T₂₀H) on the leaf surface. The results showed that under high temperature stress conditions, compared to non-high temperature adversity, the green leaf area, chlorophyll relative content (SPAD), and dry matter accumulation were significantly decreased, wheat yield was significantly reduced, spike number, and spike grain number did not change significantly, and 1000-grain weight was the dominant factor in yield reduction. Compared to water spraying, the yield after spraying trehalose was higher than that under high temperature stress, the accumulation of dry matter in various organs was increased, the content of malondialdehyde (MDA) was decreased, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were increased, and the range of change was different among varieties. The decrease of SPAD value of heat-resistant varieties was smaller than that of malondialdehyde, but the increase of CAT activity was larger, indicating the production reduction was small. Further analysis showed that the net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), SPAD, SOD, and POD had an extremely significant positive correlation with 1000-grain weight, while MDA had an extremely significant negative correlation with yield. These results suggested that high temperature stress inhibited photosynthesis in wheat by reducing P_n, G_s, and T_r, decreasing photosynthetic product production and causing eventual yield reduction. Spraying TRE, P_n, G_s, T_r, SPAD, and CAT were the main indicators to reduce the injury caused by high temperature stress, and the mitigation effect of sensitive varieties was obvious. In addition, the effect of spraying 15 mmol L^-1 trehalose at flowering stage was the best. The results could provide a theoretical basis for the mechanism of wheat photosynthetic response difference and wheat antioxidant metabolism under high temperature stress during trehalose filling stage.

Effects of different soil intensification treatments on growth and development of Radix pseudostellariae in continuous cropping system

CHEN Ting, JIAO Yan-Yang, ZHOU Xin-Ye, WU Lin-Kun, ZHANG Zhong-Yi, LIN Yu, LIN Sheng, LIN Wen-Xiong

Acta Agronomica Sinica. 2023, 49(8):  2225-2239.  doi:10.3724/SP.J.1006.2023.24155

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Continuous monoculture problems of medicinal plants are threatening the supply and quality safety of the source products in intensive traditional Chinese medicine agricultural practice. Therefore, it is of great ecological and economic significance to intensively explore the ecological restoration of conducive-disease soil. Radix pseudostellariae is a tuberous Chinese medicine that suffers from serious continuous cropping impediments under intensive cultivation. In this study, to evaluate the effects of different treatments on alleviating the continuous cropping obstacle of R. pseudostellariae and uncover the mechanism from the perspective of soil micro-ecological environment, four different soil intensification treatments including tuber reserved, fallow, flooding and rice rotation were set between two crops of R. pseudostellariae, and dynamically detected the changes of photosynthesis, stress-resistance physiology, and dry matter translocation.The results showed that, compared with fallow treatment, rice rotation treatment significantly slowed down the downtrend of soil pH, and the organic matter content in soil. The abundance of beneficial microorganisms and nitrogen cycling genes in the rhizosphere of R. pseudostellariae was increased while the pathogenic microorganisms decreased when rotated with rice in comparison with the fallow regime. This in turn led to significantly increased net photosynthetic rate and improved process of dry matter translocation of R. pseudostellariae under rice rotation treatment, indicating that the yield of R. pseudostellariae and the contents of polysaccharides and total saponins were significantly increased by 19.5%, 22.9%, and 5.8%, respectively. The improved grey T’s correlation degree analysis showed that soil pH, soil organic matter content, the abundance of specific microorganisms, the abundance of nitrogen cycling genes, the photosynthetic rate and antioxidant enzyme system in leaves of R. pseudostellariae were highly correlated with the yield of tuberous roots (Absolute correlation degree >0.6). In addition, the physiological parameters of R. pseudostellariae reflecting the growth status and the improvement of soil environment in middle and pre-phases of tuberous root greatly contributed to high-yielding formation of the medicinal plants when rotated with rice crop. Therefore, the seedling stage, early and middle tuberous root expansion stages of R. pseudostellariae were critical to alleviate the continuous cropping obstacles of R. pseudostellariae. This study also suggested that rice exudates and its residual bio-degradants entering soil ecosystem were conducive to accelerating the reconstruction of specific microflora, alleviating soil acidification, and improving nutrition sequestration after rice rotation treatment, thus resulting in the decreased environmental stress intensity, improved energy and nutrition metabolism, and optimized dry matter allocation in the growth and development prophase, consequently improved yield and quality of the medicinal plants. These results provided a theoretical basis for the ecological remediation of continuous cropping obstacles and the construction of the pivotal technology system in ecological sustainable cultivation practice.

Effect of nitrogen application rate on grain quality, wine quality and volatile flavor compounds of waxy and no-waxy wheat

LIU Qiong, YANG Hong-Kun, CHEN Yan-Qi, WU Dong-Ming, HUANG Xiu-Lan, FAN Gao-Qiong

Acta Agronomica Sinica. 2023, 49(8):  2240-2258.  doi:10.3724/SP.J.1006.2023.21038

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In order to study the effects of different nitrogen application rates on the quality of waxy and non-waxy wheat and brewing quality, the suitable nitrogen application rate for high yield and high-quality production of wheat for brewing was determined. Mianmai 902 (non-waxy) and Zhongkezinuomai 168 (waxy) were used as the experimental materials in Dayi County, Chengdu City, Sichuan Province, in 2019 and 2020. Six nitrogen application rates (0, 45, 90, 135, 180, and 225 kg hm^-2) were set to analyze their effects on the quality of wheat raw grain, brewing quality, and volatile flavor compounds. The results showed that the yield, flour quality rate, and ash content of Mianmai 902 were higher. Zhongkezinuomai 168 had higher hardness, bulk density, protein, and fat content, higher total starch and amylopectin content, lower straight branch ratio, and lower RVA characteristic parameters except that breakdown value was higher than that of Mianmai 902. Increasing nitrogen application rate significantly increased wheat yield, and the yield of both varieties reached the maximum at 225 kg hm^-2. Silty rate and bulk density decreased with the increase of nitrogen application rate, while hardness index and protein content increased. Fat and ash content were higher in 135 kg hm^-2, the total starch and amylopectin content were higher in 90-135 kg hm^-2, peak viscosity and trough viscosity decreased significantly after 135 kg hm^-2. The wine yield of the two varieties was higher in the range of 90-135 kg hm^-2 nitrogen application, but the inter-annual difference was different. The wine yield of Mianmai 902 was significantly higher than that of Zhongkezinuomai 168 in 2019, and the opposite was true in 2020. We speculated that it was related to the more rain at filling stage in 2020, the decrease of grain hardness index and the increase of silty rate of Zhongkezinuomai 168. The content of total acid and total ester in liquor brewed by Mianmai 902 was not high, and the content of fusel oil was relatively low. Zhongkezinuomai 168 was the opposite, but the fusel content was still in the safe range (≤ 0.2 g 100 mL^-1). The total acid content of liquor produced by Mianmai 902 was the highest under the treatment of 90 kg hm^-2 in the two years, and the total acid content of Zhongkezinuomai 168 was the highest under the treatment of 135 kg hm^-2 in 2020. In terms of total ester and fusel oil, the total ester content of the two varieties was relatively low under 135 kg hm^-2 treatment, and the fusel oil content was the lowest under 90 kg hm^-2 treatment. Compared with 2019, the contents of total acid and total ester of the two varieties decreased significantly in 2020, which may be related to more precipitation at grain filling stage and the decrease of total starch and amylopectin contents. Zhongkezinuomai 168 had more kinds and quantities of volatile flavor substances, and its overall brewing characteristics were better than that of Mianmai 902. The number of volatile flavor compounds of Mianmai 902 was the highest at 90 kg hm^-2, and the comprehensive score was the highest. The number of volatile flavor compounds of Zhongke Zinuomai 168 was the highest at 225 kg hm^-2, and the comprehensive score was the highest. Correlation analysis and path analysis showed that total starch content and amylopectin content were significantly positively correlated with the total acid and total ester content. Most starch physicochemical indexes played a positive indirect role in the formation of the total ester through amylose and gelatinization temperature. The results showed that the wine yield of wheat was affected by interannual factors and flour quality rate. Starch content, composition, and gelatinization characteristics had important effects on the formation of total acid and total ester, esters were the main components of volatile flavor substances, greatly affected by variety factors. Under the nitrogen application rate of 90-135 kg hm^-2, waxy and non-waxy wheat had better starch content, composition and pasting properties, and more volatile flavor substances in liquor-making, which was suitable for high yield and high quality of liquor-making wheat.

Simultaneous determination of 13 carotenoids in sweetpotato by Ultra- Performance Liquid Chromatography

JIA Rui-Xue, CHEN Yi-Hang, ZHANG Rong, TANG Chao-Chen, WANG Zhang-Ying

Acta Agronomica Sinica. 2023, 49(8):  2259-2274.  doi:10.3724/SP.J.1006.2023.24202

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Carotenoids as important indexes to evaluate the edible and process quality of sweetpotato, are crucial to promoting sweetpotato breeding. However, the lack of rapid detection methods for the compositions and contents of carotenoids in sweetpotato has limited the progress of edible quality analysis and breeding of sweetpotato. In this study, an Ultra- Performance Liquid Chromatography (UPLC) method was established for simultaneous determination of 13 carotenoids in sweetpotato by optimizing the chromatographic conditions and sample pretreatment process. The results showed that ethanol: acetone: hexane (1:1:1, v/v/v) was used as the extraction solution, and methyl tert-butyl ether was used as the dissolution solution to obtain the highest yield of carotenoids. Analysis conditions of UPLC: methanol: acetonitrile (1:3, v/v) containing 0.01% 2,6-butylated hydroxytoluene (BHT) and 0.1% formic acid as mobile phase A, methyl tert-butyl ether containing 0.01% BHT as mobile phase B gradient elution, YMC Carotenoid C30 (2 mm×100 mm, 3 μm), the flow rate was 0.8 mL min^-1, injection volume was 1 μL, the detection wavelength was 450 nm, and the analysis time was 8 min. The linear relationships of 13 carotenoids in this method were good, the correlation coefficients were all greater than 0.997. The test results of precision, repeatability, stability and recovery were all in line with the requirements. The UPLC method in this study can quickly, accurately and simultaneously detect the contents of 13 carotenoids in sweetpotato, which can lay a foundation for quality analysis of germplasm resources and breeding materials in large quantities of sweetpotato.

Hyperspectral remote sensing detection of Fusarium head blight in wheat based on the stacked sparse auto-encoder algorithm

LIN Fen-Fang, CHEN Xing-Yu, ZHOU Wei-Xun, WANG Qian, ZHANG Dong-Yan

Acta Agronomica Sinica. 2023, 49(8):  2275-2287.  doi:10.3724/SP.J.1006.2023.21060

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Fusarium head blight (FHB) has the characteristics of rapid onset and short cycle. The deep learning feature extraction method was used to establish a disease severity detection model to provide guidance for the prevention and control of FHB. The hyperspectral data of wheat ears from flowering to maturity under three varieties from 2018 to 2020 were collected. The spectral curves of wheat ears were obtained by morphological processing and multi-source scattering correction. Then spectral features of FHB were extracted by stacked sparse auto-encoder (SSAE), combined with Softmax classifier and the partial least squares regression method to detect FHB. Through pre-training, the two-layer SSAE model with 12-6 neurons performed better, the mean square error of the model was lower, and the characteristics of each disease level were significantly different. The deep learning features extracted by the trained SSAE model were the basis of the establishment of FHB disease severity level discrimination model and severity prediction model. The overall accuracy and Kappa coefficient of the model were 88.2% and 0.84, respectively, and the accuracy was the highest for the variety of ‘Huaimai 35’. The prediction coefficient of determination (R²) and root mean square error (RMSE) of the model for the test set of all varieties were 0.927 and 0.062 in the severity prediction model, respectively, and R² for each variety was around 0.95. The FHB prediction model based on SSAE deep learning features has higher accuracy than those with several common FHB spectral indices. Hyperspectral remote sensing had the characteristics of large amount of data and many spectral bands. The stack sparse auto-encoder builded a more complex model by adding the limiting conditions of sparse representation to the auto-encoder model, and increasing the number of hidden layers and hidden neurons. The extracted spectral features can better reflect the spectral characteristics of FHB in all aspects, so the detection model of FHB constructed by using these features has higher accuracy, which provides a reference for timely and accurate monitoring of FHB.

RESEARCH NOTES

Identification of the rgs1 mutant with rapid germination of seed and isolation of the regulated gene in rice

JIA Lu-Qi, SUN You, TIAN Ran, ZHANG Xue-Fei, DAI Yong-Dong, CUI Zhi-Bo, LI Yang-Yang, FENG Xin-Yu, SANG Xian-Chun, and WANG Xiao-Wen

Acta Agronomica Sinica. 2023, 49(8):  2288-2295.  doi:10.3724/SP.J.1006.2023.22056

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Rice seed absorbed water and germinated rapidly in the paddy field, which could reduce the probability of damage from the pest and germs by shortening the stay time in soil, and thus enhancing seed surviving rate and facilitating the formation of strong seedlings. To exploer the molecular mechanism of seed germination, a mutant rgs1 (exhibiting rapid seed germination, dwarfism, and multi-tillers etc) was identified by screening the EMS (ethyl methanesulfonate) induced library of Jinhui 10 (WT). The dwarfism of rgs1 originated from the shortened internodes and the characteristic of multi-tiller was caused by the rapid growth of tiller buds. Genetic analysis showed that the mutational traits of rgs1 was controlled by a single recessive nuclear gene. LOC_Os12g21710, encoding a chloroplast ζ-carotene isomerase in the mapping region, had a base substitution (G in rgs1 and A in wild type) in the third exon, resulting in the earlier termination of protein translation, which was regarded as the candidate gene of RGS1. The qRT-PCR analysis showed that, compared with WT, the relative expression levels of HTD1, D27, and D10 controlling strigolactone (SLs) synthesis and of D14 and TB1 regulating SLs signal transduction decreased significantly and the relative expression level of D53 acting as a repressor of SLs signaling increased significantly, suggesting that the mutational characteristics of rgs1 were related with the SLs pathway. The transcriptional level of OsNCED1, encoding a key enzyme of abscisic acid (ABA) synthesis, was almost absent in rgs1, while the relative expression levels of MOC3 and FON1 were significantly enhanced, indicating that the rapid seed germination of rgs1 was associated with the defect of ABA synthesis. Therefore, we predicted that RGS1 should be a key gene regulating the cooperation of SL and ABA pathway, thus regulating seed germination, plant height, and tiller number in rice.

Effects of water and nitrogen application on root characteristics and nitrogen utilization in winter wheat

LIU Shi-Jie, YANG Xi-Wen, MA Geng, FENG Hao-Xiang, HAN Zhi-Dong, HAN Xiao-Jie, ZHANG Xiao-Yan, HE De-Xian, MA Dong-Yun, XIE Ying-Xin, WANG Li-Fang, WANG Chen-Yang

Acta Agronomica Sinica. 2023, 49(8):  2296-2307.  doi:10.3724/SP.J.1006.2023.21051

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The morphological and physiological characteristics of the root system determine the ability of a plant to obtain nutrients and water. In winter wheat, to building a sensible root population structure, coordinating root-shoot growth, and improving the efficiency of N fertilizer utilization, root morphological characteristic and root activity in response to water and nitrogen (N) and their relationships with dry matter accumulation in shoots, yield, and N utilization were analyzed. A field experiment was conducted using split-plot on design two factors. Two main levels of water supply, W0 (no irrigation during the whole growth period) and W1 (irrigation once each at the jointing and flowering stages), and three secondary levels of N application [N0 (0 kg hm^-2), N180 (180 kg hm^-2), and N300 (300 kg hm^-2)] were set. Compared with W0, W1 inhibited the increase of root length density but increased the root average diameter in the 0-20 cm and 20-40 cm soil layers, increased root surface area and root dry weight density in the 0-20 cm soil layer, significantly increased root activity by 4.98%-22.7%, reduced root-shoot ratio by 1.47%-11.25%, and yield, N uptake efficiency, and partial productivity of N fertilizer increased by 15.50%, 13.40%, and 14.91%, respectively. Compared with N0, N application promoted root growth, significantly increased the average root diameter, root length density, root surface area, root dry weight density, and root activity, while decreasing the root-shoot ratio. N180 was more beneficial to root growth than N300, N180 improved root morphological indicators and activity, while increasing yield, N uptake efficiency and agronomic use efficiency of N fertilizer by 2.53%, 44.51%, and 39.37%, respectively. Correlation analysis revealed that root dry weight density from jointing stage to flowering stages was positively correlated with the yield and N use efficiency, while the root-shoot ratio was negatively correlated with yield and positively correlated with N use efficiency. Therefore, appropriate levels of irrigation and N application optimized root morphology and distribution, improved root activity, coordinated root and shoot dry matter distribution and improved yield and N utilization. In winter wheat production, W1N180 is beneficial to promote the synergistic improvement of yield and N use efficiency.

High motif EST-SSR markers development and genetic diversity evaluation for 200 core germplasms in proso millet

WANG Qian, ZHANG Li-Yuan, XU Yue, LI Hai, LIU Shao-Xiong, XUE Ya-Peng, LU Ping, WANG Rui-Yun, LIU Min-Xuan

Acta Agronomica Sinica. 2023, 49(8):  2308-2318.  doi:10.3724/SP.J.1006.2023.24201

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The objective of this study is to clarify the genetic background for the core germplasm resources of proso millet and to evaluate the genetic diversity from different ecological regions in China. To provide a basis for accelerating proso millet breeding process and mining excellent germplasm, a new high motif EST-SSR markers were developed. In this study, 200 high motif EST-SSR markers were developed based on transcriptome sequencing results, and used to evaluate the genetic diversity for 200 core germplasm accessions of proso millet. Results showed that 52 of the 200 markers were polymorphic in 6 proso millet accessions with significant geographical differences, with the development efficiency of 26%, including 17 tetra-nucleotide repeat SSRs (32.7%), 17 penta-nucleotide repeat ones (32.7%), and 18 hexa-nucleotide repeat ones (34.6%). Among the examined 200 accessions, a total of 129 observed alleles were detected in 52 loci, changed 2-3 alleles at each locus. The Shannon diversity index was 0.3093-1.0910, with an average of 0.7277. The polymorphism information content was 0.1948-0.8211, with an average of 0.5104. Based on UPGMA, the 200 proso millet accessions were divided into six groups. Based on Structure (K=7), proso millet were mainly from four gene pools in Northeast, Northern, Loess Plateau, and North China. Based on principal component analysis, the accessions were classified into six clusters, consistent with the geographic region. This study constructed a set of 52 tetra-, penta- and hexa-nucleotide repeat EST-SSR markers, with the efficiency of 26%. Based on the above markers, genetic diversity of proso millet for landrace core germplasm was abundant.