Table of Content

12 June 2021, Volume 47 Issue 6

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SPECIAL SECTION: GENOMICS AND GENETIC IMPROVEMENT IN MAIN BAST FIBER CROPS

Editorial: Strengthening the researches of genomics of bast fiber crops to promote elite allele mining and germplasm innovation

Zhang Li-wu

Acta Agronomica Sinica. 2021, 47(6):  993-996.  doi:10.3724/SP.J.1006.2021.04993

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Genomics and genetic improvement in main bast fiber crops: advances and perspectives

XU Yi, ZHANG Li-Lan, QI Jian-Min, ZHANG Lie-Mei, ZHANG Li-Wu

Acta Agronomica Sinica. 2021, 47(6):  997-1019.  doi:10.3724/SP.J.1006.2021.04121

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With the development of sequencing technology, main bast fiber crops (jute, kenaf, ramie, flax, and hemp) have completed genome sequencing from 2011 to 2020, which marks that the science of bast fiber crops has entered the era of genome. Firstly, this paper reviews the genome sequencing of bast fiber crops. Secondly, the important gene identification of bast fiber crops is also reported. Based on reference genome and transcriptome sequencing, a large number of candidate genes related to fiber development and response to abiotic stress have been detected, corresponding to the species characteristics of bast fiber and the adversity agriculture of “not competing with food”. Meanwhile, candidate genes for specific bast fiber crops have also been identified, such as male fertility in kenaf, seed oil content in flax, cannabinoid related candidate genes. Thirdly, the completion of bast fiber crop genome sequencing provides the possibility of omics-based genetic improvement, which will facilitate to study the formation of bast fiber and evolution mechanisms of bast fiber crop germplasms and systematically analyze the molecular basis for the formation of agronomic traits such as fiber yield, fiber quality, disease resistance, and stress tolerance. Also, it will facilitate to establish a high-throughput genotype-phenotype database, mine excellent gene resources, and create new germplasm. Moreover, it will facilitate to establish efficient rapid breeding technology systems by the innovation and combination of molecular marker-assisted selection, genome selection, transgenic technology and so on. To meet the market demand particularly bast fiber crop-related industries and adapt to the production model of bast fiber crops, we should breed new bast fiber crop varieties with high yield, high efficiency, stress resistance, disease resistance, suitable for light simplification and mechanization cultivation, high quality, and special purpose. Although the important information of gene resources and loci has been obtained from the reference genomes, there are still a series of challenges that how to utilize the existing resources efficiently for genetic improvement of bast fiber crops, such as stable and efficient genetic transformation system, construction of gene editing system, and genome selection breeding.

Characterization of the expression profiling of circRNAs in the barks of stems in ramie

LI Fu, WANG Yan-Zhou, YAN Li, ZHU Si-Yuan, LIU Tou-Ming

Acta Agronomica Sinica. 2021, 47(6):  1020-1030.  doi:10.3724/SP.J.1006.2021.04042

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Ramie [Boehmeria nivea (L.) Gaud.] is a special natural fiber crops in China, and its fiber has many excellent characteristics, including long strands and well tensile strength. Elucidation of the mechanism for fiber formation will be helpful for the improvement of fiber yield and quality in ramie. In this study, the expressed analysis of circular RNA (circRNA) for the tissues of barks from the top stems and middle stems were performed by Illumina sequencing, respectively. The total of 5268 circRNAs were identified. Among these circRNAs, 78 showed differential expression between two examined tissues. Previous cytological observation suggested that the secondary cellular walls (SCWs) of fiber cells from the top of the ramie stems did not initiate growth and those from middle part of the ramie stems were thickening. Therefore, we speculated that these 78 differentially expressed circRNAs were potentially involved in the fiber development in ramie. The results provide an important basis for understanding the role of circRNA in the regulation of fiber development.

Physiological characteristics and DNA methylation analysis under lead stress in kenaf (Hibiscus cannabinus L.)

LI Zeng-Qiang, DING Xin-Chao, LU Hai, HU Ya-Li, YUE Jiao, HUANG Zhen, MO Liang-Yu, CHEN Li, CHEN Tao, CHEN Peng

Acta Agronomica Sinica. 2021, 47(6):  1031-1042.  doi:10.3724/SP.J.1006.2021.04104

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DNA methylation plays an important role in response to plant biotic and abiotic stresses, but there are few reports on the changes of plant DNA methylation level under lead stress. In this study, kenaf (Hibiscus cannabinus L.) P3A was used as the material, the seedlings were cultured in Hoagland solution, and treated with at different concentrations (0, 200, 400, and 600 μmol L ^-1) of PbCl₂. The changes of agronomic traits, ROS content and antioxidant enzyme activity of root were investigated. The changes of DNA methylation level in roots under 600 μmol L ^-1 lead stress were determined by methylation-sensitive amplification polymorphism (MSAP). The differentially methylated genes (DMGs) were cloned, sequenced, and functionally annotated. In addition, the expression levels of DMGs were investigated by qRT-PCR. The results showed that the stem diameter, root length and root surface area of seedlings were significantly inhibited by different concentrations of PbCl₂ stress. And the plant height and total fresh weight of kenaf seedlings were significantly reduced under 400 μmol L ^-1 concentration or more of lead stress. The content of lead, O₂ ^? and MDA, and activities of SOD were increased significantly in kenaf seedlings roots, CAT activity increased first and then decreased with the increase of lead concentration, the POD activity showed a trend of decreasing first and then increasing. MSAP analysis of roots treated with 0 μmol L ^-1 and 600 μmol L ^-1 PbCl₂ showed that DNA methylation rates were 71.13%, 62.20%, fully methylated ratio was 50.52%, 37.80%, and hemi-methylated ratio were 20.62%, 24.40%, respectively. In other words, lead stress significantly reduced DNA methylation rate and total methylation rate, whereas increased the hemi-methylation rate of roots of kenaf seedlings. qRT-PCR analysis showed that there were also differences in gene expression of seven DMGs closely related to resistance. It suggested that the change of DNA methylation level played an important role in kenaf response to lead stress in kenaf. This study provides a theoretical basis for further exploring the potential mechanism of DNA methylation in response to plant abiotic stress, and improving soil lead pollution in kenaf production.

Creation of male sterile germplasm using the partial length gene of HcPDIL5-2a in kenaf

ZHOU Bu-Jin, LI Gang, JIN Gang, ZHOU Rui-Yang, LIU Dong-Mei, TANG Dan-Feng, LIAO Xiao-Fang, LIU Yi-Ding, ZHAO Yan-Hong, WANG Yi-Ning

Acta Agronomica Sinica. 2021, 47(6):  1043-1053.  doi:10.3724/SP.J.1006.2021.04069

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In order to create transgenic male sterile germplasm in kenaf, the partial length of gene HcPDIL-2a was transformed into maintainer line 722HB via pollen tube pathway. A low-temperature sensitive male sterile mutant called ‘722THS’ was accquired, which showed sterile when grown in winter in Hainan and fertile when grown in summer in Nanning, and a stable Genic Male Sterile (GMS) line 722HS was selected from its sister progenies. A cytoplasmic male sterile line 722HA was bred by crossing the mutant 722THS with the wild type 722B. Cytological observation indicated that the microspore abortion of 722THS and 722HA both happened at dinuclear stage. The mitochondrial DNA molecular tag revealed that mitochondrial DNA rearrangement occurred in 722HA, while mitochondrial DNA of 722THS and 722B remained unchanged. This study provided a new way for the creation of male sterile germplasms, which had important scientific significances and broad application prospects.

Genome-wide identification of GRAS transcription factor and expression analysis in response to cadmium stresses in hemp (Cannabis sativa L.)

YIN Ming, YANG Da-Wei, TANG Hui-Juan, PAN Gen, LI De-Fang, ZHAO Li-Ning, HUANG Si-Qi

Acta Agronomica Sinica. 2021, 47(6):  1054-1069.  doi:10.3724/SP.J.1006.2021.04078

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GRAS transcription factors play important roles in plant growth, development and stress responses. In order to systematically analyze the GRAS transcription factor family in hemp, we performed a genome-wide identification of hemp GRAS genes, analyzed their physical and chemical properties, phylogenetic development, gene structure, and GRAS gene expression under cadmium stress in two hemp varieties (Yunma 1 and Inner Mongolia Xiaolidama). The results showed that there were 54 GRAS transcription factors in hemp genome, with the protein length from 415 to 757, encoding 96.30% of acidic proteins, the molecular weight from 46,405.05 to 85,748.52 kD and the isoelectric point from 4.77 to 8.54. These transcription factors were divided into nine subfamilies, among which, PAT1, LS, SHR, and HAM were more conserved, PAT1, LISCL, and CsGRASA had a large number of tandem repeats of genes, and CSGRAS12 genes were all present in collinearity analysis of five plants. Yunma 1 and Inner Mongolia Xiaolidama were treated with cadmium stress. Plant height and the fresh weight decreased in Yunma 1 and Inner Mongolia Xiaolidama, by 10.48%, 6.33% and 66.07%, 42.67%, respectively, indicating that Yunma 1 was more tolerant than Inner Mongolia Xiaolidama under cadmium stress. Among 54 GRAS genes in Yunma 1, 42 genes (77.78%) were up-regulated by 1.05-18.10, and 11 genes (20.37%) were down-regulated by 0.13-0.91. Among 54 GRAS genes in small-grain cannabis in Inner Mongolia, 27 genes (50.00%) were up-regulated by 1.01-6.46, and 27 genes (50.00%) were down-regulated by 0.30-0.96. This study showed that the 40 homologous GRAS gene in Yunma 1 were significanlty up- or down-regulated than those in Inner Mongolia Xiaolidama under cadmium stress, indicating that these GRAS genes were significantly related to cadmium stress. This study can provide a reference for subsequent mining and verification of GRAS genes in hemp.

Transcriptome profiling of flax (Linum usttatissimum L.) response to low potassium stress

HUANG Wen-Gong, JIANG Wei-Dong, YAO Yu-Bo, SONG Xi-Xia, LIU Yan, CHEN Si, ZHAO Dong-Sheng, WU Guang-Wen, YUAN Hong-Mei, REN Chuan-Ying, SUN Zhong-Yi, WU Jian-Zhong, KANG Qing-Hua

Acta Agronomica Sinica. 2021, 47(6):  1070-1081.  doi:10.3724/SP.J.1006.2021.04133

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Potassium (K) is an essential element for the growth and development in flax. Transcriptome sequencing and qRT-PCR were used to investigate the regulation of differential gene expression after 12 h and 96 h of low-K ⁺ treatment. The results showed that the leaf edge of flax treated with low-K ⁺ for 7 days turned yellow, and the plants were dwarfed compared with the control. LusKC1 (Lus K channel 1), LusSKOR (Lus STELAR K ⁺ outward rectifier) and LusHAK5 (Lus high affinity K ⁺ transporter 5) were detected to respond to low-K ⁺ with response peak time of 12 h and 96 h. Compared with the control, 1154 differentially expressed genes (DEGs) (508 up-regulated and 646 down-regulated genes) were identified in low-K ⁺ treatment for 12 h. GO enrichment showed that DEGs were mainly concentrated on five categories: metabolic process, cellular process, single biological process, catalytic activity and binding function. KEGG pathway enrichment showed that DEGs involved in energy metabolism, carbohydrate metabolism, carbon metabolism, amino acid metabolism, terpenoid metabolism and plant hormone signal transduction pathways. Furthermore, 7 genes directly related to K (4K transporters, 2K channel proteins and 1 sodium-potassium-calcium exchanger protein), 13 genes related to hormone and 6 genes related to cellulose synthesis were screened. Among the 7 genes directly related to K, the relative expression of 2 genes were up-regulated by 1.75 and 2.64 times and 5 genes down-regulated by 1.21-9.57 times. In summary, DEGs preliminarily revealed the transcriptional regulation pathway involved in low-K ⁺ in flax, which laid a foundation for cloning and functional verification of flax low-K ⁺ tolerance related genes.

Identification and expression of PAL genes in sisal

HUANG Xing, XI Jin-Gen, CHEN Tao, QIN Xu, TAN Shi-Bei, CHEN He-Long, YI Ke-Xian

Acta Agronomica Sinica. 2021, 47(6):  1082-1089.  doi:10.3724/SP.J.1006.2021.04116

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Sisal is an important fiber crop in tropical areas, but its research foundation of molecular biology is relatively weak, and the mechanism of fiber development still remains unclear. Phenylalanine ammonia-lyase (PAL) is the first enzyme of lignin bio-synthesis, which is an important component of fiber. According to published transcriptome data, two sisal PAL genes with complete coding sequences were successfully identified. Their expression patterns during sisal leaf development were consistent with previously reported PAL activity changes during fiber development, indicating that PAL was closely related to lignin bio-synthesis. Phylogenetic analysis showed that sisal PALs were closely related with Agave americana. Selection pressure analysis showed similar selection pressure of PALs in sisal and A. americana, which were higher than those in A. tequilana. This might be caused by the convergent evolution of fiber-related traits in sisal and A. americana. In addition, sisal PALs were not significantly expressed under neither copper nor lead stress, which might be caused by post-transcriptional regulation under heavy metal stresses. It was worth noting that the expression of sisal PALs was highly up-regulated after Phytophthora nicotianae Breda inoculation. Sisal PALs might participate in the bio-synthesis of disease resistance-related secondary metabolites in phenylpropanoid pathway, as well as plant cell-wall mediated immunity. Therefore, functional characterization of sisal PALs could improve the understanding of mechanisms in fiber development and disease resistance, which is of great importance for breeding new sisal varieties with high yield, high quality and multiple resistance.

Expression analysis of abiotic stress response gene HcWRKY71 in kenaf and transformation of Arabidopsis

LI Hui, LI De-Fang, DENG Yong, PAN Gen, CHEN An-Guo, ZHAO Li-Ning, TANG Hui-Juan

Acta Agronomica Sinica. 2021, 47(6):  1090-1099.  doi:10.3724/SP.J.1006.2021.04201

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WRKY transcription factor plays an important role in plant responded to abiotic stress. In this study, the unigene sequence (CL3883.Contig4) of the transcriptome in kenaf was used as a reference. Primers were designed for PCR amplification. The full length of HCWRKY71 gene was 957 bp obtained by the sanger sequencing. HCWRKY71 gene had an open reading frame length of 957 bp, and encoded a protein containing 318 amino acids, with a conserved functional domain of WRKY, which belonged to WRKY transcription factor II. Under the salt stress, its relative expression level increased with the increase of NaCl concentration; under the drought stress, with the extension of drought time, the relative expression of the HcWRKY71 gene first decreased, then increased and finally decreased; under the stress of heavy metal cadmium, its expression decreased with the increase of CdCl₂ concentration, indicating that the expression of the gene was induced by salt, drought and heavy metal cadmium stress. The gene was transformed into Arabidopsis by Agrobacterium-mediated inflorescence impregnation. It was found that the HcWRKY71 gene improved the salt tolerance of transgenic Arabidopsis seedlings. This laid a solid foundation for further study of stress tolerance mechanism of HcWRKY71 gene.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic analysis of fat content based on nested populations in peanut (Arachis hypogaea L.)

HUANG Bing-Yan, SUN Zi-Qi, LIU Hua, FANG Yuan-Jin, SHI Lei, MIAO Li-Juan, ZHANG Mao-Ning, ZHANG Zhong-Xin, XU Jing, ZHANG Meng-Yuan, DONG Wen-Zhao, ZHANG Xin-You

Acta Agronomica Sinica. 2021, 47(6):  1100-1108.  doi:10.3724/SP.J.1006.2021.04138

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Nested populations can be used to dissect the heredity of complex traits. The genetic models of fat content of F_2:3 families in nested combinations with one common parent and six founder parents were analyzed, aiming to detect the genetic differences among the founders and to provide bases for breeding strategy for fat content improvement in peanut kernels. The common parent was Yuhua 15, an irregular-type variety with high fat content, and the other six founder parents were different botanical varieties with different fat contents. The results showed that the genetic model of fat content traits was different in different combinations. Six crosses were in accordance with three genetic patterns, including none major gene model, one major gene model with additive and dominant effect, and two major genes model with equal additive and dominant effect. The estimated values of various genetic effects were also different. The heritability of the main genes ranged from 32% to 80%, indicating that the gene loci controlling the fat content and their segregation patterns were different in different F_2:3 populations. There were more individuals with high fat content in the offspring from combinations with both parents of high fat content. However, the heritability was low and phenotypic selections for fat content were not suggested in the early generations in such combinations. The offspring from combinations with parents of significantly different fat content had a larger variation range in fat content, and phenotypes with variable fat content were available. In this study, the large variances in the nested populations demonstrated the genetic complexity of fat content and the characteristics of multi major gene regulation. These results provide a comprehensive base for understanding the genetics and regulation of fat content, and the nested populations will be helpful in further QTL detection of fat content in peanut.

Characterization of aphid-resistance of a hairy wild Brassica oleracea taxa, B. incana

ZUO Xiang-Jun, FANG Peng-Peng, LI Jia-Na, QIAN Wei, MEI Jia-Qin

Acta Agronomica Sinica. 2021, 47(6):  1109-1113.  doi:10.3724/SP.J.1006.2021.04147

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Brassica oleracea contains important vegetables varieties in our daily life, however, the production of Brassica vegetables always suffers from aphids. Identifying resistant resource and understanding corresponding resistance mechanism are of great importance for resistance breeding of crops. In our previous study, a wild relative of B. incana with dense trichomes on leaves and stem was obtained. In the present study, to investigate the resistance of B. incana to aphids and to understand the role of trichomes in resistance, the two parental accessions and their F_2:3 lines were inoculated with aphids in lab condition. The results showed that the egg production and lifespan of aphids on hairless leaves (36.7 eggs and 22.2 days) were significantly higher than corresponding values on hairy leaves (8.1 eggs and 13.1 days). To investigate whether a chemical role contributed to the resistance, the contact toxicity, gastric toxicity and anti-feeding ability of the leaf extracts were checked between hairy and glabrous F_2:3 lines. None of the extract was found to be with significant contact toxicity and gastric toxicity to aphids, whereas the number of aphids on leaves treated with extract from hairy B. oleracea was significantly lower than that treated by extract of glabrous leaves. This study revealed that the resistance of B. incana to aphids might attribute to both the physical inhibition from trichomes and the avoidance role of its chemical compounds.

Genome-wide association study of blast resistance loci in the core germplasm of rice landraces from Guangxi

CHEN Can, NONG Bao-Xuan, XIA Xiu-Zhong, ZHANG Zong-Qiong, ZENG Yu, FENG Rui, GUO Hui, DENG Guo-Fu, LI Dan-Ting, YANG Xing-Hai

Acta Agronomica Sinica. 2021, 47(6):  1114-1123.  doi:10.3724/SP.J.1006.2021.02047

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Blast disease is one of the most important rice diseases, which seriously affects the yield and quality in rice. In general, breeding resistant varieties is the most economical, environmental, and friendly way to control rice blast. Identification and mining of blast resistance genes are the basis and premise of disease resistance breeding. In our previous study, 419 core germplasms from Guangxi rice landraces were sequenced using specific-locus amplified fragment sequencing (SLAF-seq) technology, and 208,993 high-quality SNPs were identified. Spray inoculation at seedling stage was used to evaluate the resistance of the 419 germplasms to 7 strains. According to phenotype and genotype data, genome-wide association study (GWAS) for rice blast was performed using general linear model (GLM) and mixed linear model (MLM). A total of 20 loci were detected under the two models, including 20 loci detected by GLM and 1 locus detected by MLM. Chr12_10803913 locus was detected in both models. There were 17 loci, overlapping with previously reported genes/QTLs, while the remaining three loci were the first reported, including Chr3_18302718, Chr3_18302744, and Chr5_10379127. A total of 323 candidate genes were screened out in the genomic regions of 150 kb upstream and downstream of 20 significantly associated loci. Eight candidate genes were preliminarily determined to be related to disease resistance. Among them, both LOC_Os12g18360 (Pita) and LOC_Os12g18729 (Ptr) were known cloned genes, LOC_Os03g32100, LOC_Os03g32180, and LOC_Os05g18090 were selected as candidate genes near the three loci. The results provided the scientific basis for the mining of rice blast resistance loci and gene cloning.

Expression pattern analysis of genes related to lipid synthesis in peanut

XU Jing, PAN Li-Juan, LI Hao-Yuan, WANG Tong, CHEN Na, CHEN Ming-Na, WANG Mian, YU Shan-Lin, HOU Yan-Hua, CHI Xiao-Yuan

Acta Agronomica Sinica. 2021, 47(6):  1124-1137.  doi:10.3724/SP.J.1006.2021.04150

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In order to survey the regulation patterns of genes expression in the synthesis of oil at different developmental stages in peanut seed, F18 (high-oleic medium oil peanut variety) and ‘Luhua 6’ (low-oleic acid low oil variety) were used as research materials. The expression pattern analysis of genes was performed for peanut seeds on the 10, 30, 40, and 60 DAP, respectively. The results indicated that 130, 3556, and 2783 genes were significantly differentially expressed in the two varieties (lines) on the 30, 40, and 60 DAP, respectively. GO annotation and KEGG enrichment showed that DEGs were mainly enriched in the fatty acid synthesis and photosynthetic pathways, such as FAB2, FAD2, WRI1 genes, which were involved in the accumulation of oleic acid. All the genes involved in photosynthesis pathway were photochlorophyll binding proteins and all of them were up-regulated. KEGG pathway indicated that all the genes involved in fatty acid biosynthesis pathway on the 40 DAP and 60 DAP were up-regulated. In summary, these results provide a theoretical basis for molecular study of fatty acid synthesis in the development stage of peanut seeds and offer some candidate genes as gene resources of quality improvement in peanut breeding.

A study of expression pattern of auxin response factor family genes in maize (Zea mays L.)

LI Wen-Lan, LI Wen-Cai, SUN Qi, YU Yan-Li, ZHAO Meng, LU Shou-Ping, LI Yan-Jiao, MENG Zhao-Dong

Acta Agronomica Sinica. 2021, 47(6):  1138-1148.  doi:10.3724/SP.J.1006.2021.03043

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Auxin response factors (ARFs) are important transcription factors which control the expression of target genes by binding specifically to auxin response elements, and are involved in a series of developmental processes in plant species. In maize genome, dozens of ARF genes are encoded, however, there is little known on their expression patterns. In this study, the analysis on the expression level of ARF genes in diverse tissues and organs revealed that expression level of 32 ARF genes were higher in reproductive organs than that in vegetative organs, except ARF10, ARF16, and ARF34 constitutively expressed. The predicted results of cis-acting elements showed that the promoter regions of 28 ARF genes harbored the cis-regulatory elements related to abiotic stresses. Real-time quantitative PCR results indicated that expression of several ARF genes showed a response to cold, heat, and osmotic stresses, respectively. The results highlighted the importance of ARF family genes in reproductive growth and abiotic stress response, and provided useful information for the comprehensive analysis of the biological function of ARF genes in maize.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of whole soil-plastic mulching system and fertilization rates on water consumption characteristics and yield of tartary buckwheat in arid land

FANG Yan-Jie, ZHANG Xu-Cheng, HOU Hui-Zhi, YU Xian-Feng, WANG Hong-Li, MA Yi-Fan, ZHANG Guo-Ping, LEI Kang-Ning

Acta Agronomica Sinica. 2021, 47(6):  1149-1161.  doi:10.3724/SP.J.1006.2021.01059

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In order to study the effects of whole soil-plastic mulching planting and different fertilization rates on soil water consumption characteristics and yields of tartary buckwheat, a three-year (2015-2017) located experiment was carried out in semi-arid region of east-central Gansu Province, China, under whole soil-plastic mulching planting system. Four fertilization treatments under soil-plastic mulching were accordingly designed, including high application rate (HF, N 120 kg hm^-2+ P₂O₅ 90 kg hm^-2 + K₂O 60 kg hm^-2), medium rate (MF, N 80 kg hm^-2+ P₂O₅ 60 kg hm^-2 + K₂O 40 kg hm^-2), low rate (LF, N 40 kg hm^-2+ P₂O₅ 30 kg hm^-2 + K₂O 20 kg hm^-2), and zero fertilization rate (ZF), whereas ZF with traditional non-mulching planting was set as the control (CK) to illustrate the effects of soil-plastic mulching and fertilization on water consumption characteristics, yields and water use efficiency (WUE) of tartary buckwheat in semi-arid area of China. The results showed that the effects of rainwater collection and soil moisture conservation were obvious after planting tartary buckwheat with whole soil-plastic mulching, which also improved soil water environment and increased pre-anthesis soil water storage (SWS, mm). LF was able to regulate soil water consumption before and after anthesis stage according to different precipitation years and soil moisture conditions. Compared with ZF, MF, HF, and CK in dry years, LF improved post-anthesis SWS by 2.8-23.5 mm and increased crop pre-anthesis water consumption in the 0-100 mm soil profile by 26.3-32.4 mm in tartary buckwheat. As a result, LF increased total crop water consumption in the whole growth period by 44.5 mm, and boosted water consumption module coefficient and intensity. Moreover, compared with ZF, MF, HF and CK, LF treatment increased dry matter weight at maturity stage by 1.2%-58.8%, leaf area index (LAI) at filling stage by 4.1%-68.5%, grain weight per plant by 1.6%-61.6%, plumpness rate by 0.6%-29.2%, biomass yield by 1.1%-182.5%, grain yield by 1.1%-130.4%, and water use efficiency (WUE, kg hm^-2 mm^-1) by 0.3%-102.7%, respectively. In conclusion, the storage effect of low amount fertilizer treatment for tartary buckwheat planting with whole soil-plastic mulching in dry land was obvious, which could achieve the coupling effects of soil moisture and fertilizer and regulate crop water consumption according to the environmental conditions such as precipitation during crop growth period, and it could significantly improve the biomass yield, grain yield and WUE of tartary buckwheat. Therefore, it was a suitable cultivation mode for yield-increasing and efficiency-boosting of tartary buckwheat in semi-arid area.

Effects of nitrogen fertilizer in whole growth duration applied in the middle and late tillering stage on yield and quality of dry direct seeding rice under “solo-stalk” cultivation mode

ZHAO Jie, LI Shao-Ping, CHENG Shuang, TIAN Jin-Yu, XING Zhi-Peng, TAO Yu, ZHOU Lei, LIU Qiu-Yuan, HU Ya-Jie, GUO Bao-Wei, GAO Hui, WEI Hai-Yan, ZHANG Hong-Cheng

Acta Agronomica Sinica. 2021, 47(6):  1162-1174.  doi:10.3724/SP.J.1006.2021.02052

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In a rice-wheat cropping system, dry direct seeding rice growth was directly affected by harvest dates of the previous crop of wheat, the return of full wheat straw to the field, and the poor quality of tillage and land preparation. A “solo-stalk” cultivation mode with main stem panicles by late sowing dates, large sowing rates and high basic seedlings was commonly used in dry direct seeding. However, the nitrogen fertilizer management of high-quality and high-yield dry direct-seeding rice for the “solo-stalk” cultivation mode was still lacking in systematic research. With high-quality japonica rice Nanjing 9108, 380×10⁴ hm^-2 basic seedlings were realized by mechanical dry direct seeding method. The leaf age treatments of 6, 7, 8, 9, and 10 leaf age and nitrogen application amount treatments of 180 and 225 kg hm^-2 were designed with accurate quantitative nitrogen management (total nitrogen was 270 kg hm^-2, base fertilizer:tiller fertilizer:spike fertilizer = 3.5:3.5:3.0) at basic seedlings of 380×10⁴ and 300×10⁴ hm^-2 as the control. Then dry direct seeding rice yield and quality were systematically determined and compared with the control and “solo-stalk” cultural method with nitrogen fertilizer in whole growth duration applied in middle and late tillering stage. The results showed that rice yield showed a trend of first increased and then decreased with nitrogen application at bigger leaf age. Rice yield was significantly higher than other treatments when applying nitrogen fertilizer at the 8-leaf stage, and the yield was further improved with the increase of nitrogen application amount. Compare with the controls, nitrogen fertilizer in whole growth duration of 180 kg N hm^-2 applied one time at 8-leaf stage could significantly increase rice yield by 5.10% and 8.65%, and reduced nitrogen fertilizer by 33.3%, whereas nitrogen fertilizer in whole growth duration of 225 kg N hm^-2 applied two time at 8-leaf stage and 7 days later could significantly increase rice yield by 7.46% and 11.09%, and reduced the nitrogen by 16.7%. The reason was that, compared with the control, seed setting rate and 1000-grain weight, effective panicle number was significantly increased resulting in the increasing total spikelet amount per hectare and yield on the basis of maintaining larger panicle type. With nitrogen applied at bigger leaf age, the head rice rate, chalkiness and protein content of rice revealed an increasing trend, but the amylose content and taste value of rice showed a decreasing trend. Compare to the two controls, the processing quality of rice with the head rice rate was increased by 0.67%-2.23% with nitrogen fertilizer in whole growth duration applied at 8-leaf age; the appearance quality was improved with the chalkiness decreased by 3.6%-14.5%; the nutrition quality was better with protein content increased by 3.03%-14.08%; the cooking and eating quality showed a tendency of getting better with amylose content decreased by 4.23%-10.95%; and there was no insignificant difference in taste value. In conclusion, nitrogen fertilizer in whole growth duration applied at suitable leaf age in the middle and late tillering stage could improve the quality and increase the yield of dry direct seeding rice under “solo-stalk” cultural method caused by late sowing dates, large sowing rate, and high basic seedlings in a rice-wheat cropping system.

Effects of nitrogen application rate on photosynthetic characteristics and yield of mung bean under the proso millet and mung bean intercropping

DANG Ke, GONG Xiang-Wei, LYU Si-Ming, ZHAO Guan, TIAN Li-Xin, JIN Fei, YANG Pu, FENG Bai-Li, GAO Xiao-Li

Acta Agronomica Sinica. 2021, 47(6):  1175-1187.  doi:10.3724/SP.J.1006.2021.04148

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To explore the effect of nitrogen (N) on the leaf gas exchange, chlorophyll fluorescence, nitrogen characteristics and yield of mung bean under intercropping with proso millet, the field experiments were conducted in 2018 and 2019 using split-plot design with two cropping patterns [proso millet-mung bean intercropping (PM) and soled mung bean (SM)] and four total N fertilizer application rates [0 (N0), 45 (N1), 90 (N2), and 135 kg hm^-2(N3)]. Under N application, the net photosynthetic rate (P_n) and transpiration rate (T_r) of mung bean in intercropping increased by 10.5%-24.5% and 15.2%-29.5% on average, which improved the photosynthetic characteristics. Maximum photochemical efficiency (F_v/F_m) and actual photochemical efficiency (Φ_PSII) increased by 2.9%-7.8% and 11.7%-28.4%, respectively, and PSII non-photochemical quenching coefficient (NPQ) decreased by 10.3%-17.4%. The chlorophyll fluorescence parameters were improved, resulting in enhancing the ability to capture and utilize light energy, and the activity of PSII reaction center was enhanced. Leaf area per plant, N content per unit dry mass of leaves (N_mass) and N content per unit area (N_area) increased first and then decreased with the increase of N application rate. The content of Chl a and Chl b increased. Photosynthetic N-use efficiency (PNUE) decreased compared with N0. N application significantly increased the dry matter accumulation and pods of mung bean in intercropping. Under the treatment of N1, N2, and N3, 100-grain weight and yield were increased by 1.1%-6.9% and 9.3%-19.7%, respectively. In the two-year trial intercropping, the land equivalent ratio of each treatment was 1.63-2.07, indicating the yield advantage of intercropping. N application could improve the photosynthetic production capacity of mung bean in intercropping and effectively regulate the adaptive response of photosynthetic system to shading. The response of photosynthetic performance of intercropping to N fertilizer was greater than that of single-plant systems. Under the conditions of this experiment, the proso millet and mung bean intercropping model can increase land productivity, and it can be used as a planting model to promote dry farming in northwestern China. The intercropping mung bean had the best photosynthetic characteristics at 90 kg hm^-2, which showed the highest yield, and the largest land equivalent ratio.

RESEARCH NOTES

Effect evaluation of QTL Qph.nau-5B controlling plant height in wheat

HAN Yu-Zhou, ZHANG Yong, YANG Yang, GU Zheng-Zhong, WU Ke, XIE Quan, KONG Zhong-Xin, JIA Hai-Yan, MA Zheng-Qiang

Acta Agronomica Sinica. 2021, 47(6):  1188-1196.  doi:10.3724/SP.J.1006.2021.01053

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Plant height affects directly the yield potential of wheat, and constitutes an important component of plant resistance to lodging. Although a large number of QTLs for plant height were detected, most of them have not been evaluated for their genetic effects yet. In the previous study, a major QTL Qph.nau-5B controlling wheat plant height was identified through association mapping in wheat variety collection. To evaluate the dwarfing effect of this QTL, three near-isogenic lines (NILs) with different alleles of Qph.nau-5B were developed using marker-assisted selection with Nanda 2419, Jichun 1016, and Zhengmai 9023 as donor and Zhongyou 9507 as receptor. The recipient genome compositions of these NILs were higher than 93%. Seven independent field trials were conducted and revealed that, compared with the recurrent parent, all NILs indicated a significant decrease in plant height (11.1 cm or 10.3% on average). Three alleles of Qph.nau-5B showed different degrees of dwarfing effects. The alleles coming from Jichun 1016 and Zhengmai 9023 displayed a similar effect on plant height (12.4 cm) in all environments, stronger than that of Nanda 2419 (8.6 cm). However, the relative dwarfism effects of different alleles were affected by different environments. Further analysis elucidated that this QTL had little detrimental influence on other agronomical traits such as spike number per plant, spike length and 1000-grain weight. These results suggested the breeding value of Qph.nau-5B that would be utilized for molecular design breeding of plant architecture in wheat.

Transformation and molecular identification of maize phytochrome A1 gene (ZmPHYA1) in cotton

MA Yan-Bin, WANG Xia, LI Huan-Li, WANG Pin, ZHANG Jian-Cheng, WEN Jin, WANG Xin-Sheng, SONG Mei-Fang, WU Xia, YANG Jian-Ping

Acta Agronomica Sinica. 2021, 47(6):  1197-1202.  doi:10.3724/SP.J.1006.2021.03037

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In order to evaluate the potential value of maize phytochrome A1 gene (ZmPHYA1) in the improvement of cotton germplasm resources, we transferred it into upland cotton (Gossypium hirsutum L.) R15 via Agrobacterium tumefaciens-mediated transformation with glufosinate-resistance gene as selection marker. The regenerated cotton plants were obtained through callus induction, antibiotic resistance screening and differentiation induction. After screening the regenerated plants by the herbicide glufosinate ammonium in the field, PCR detection confirmed that both the target bands, including 256 bp of the glufosinate gene and 217 bp band of ZmPHYA1 gene, were detected in the homozygous transgenic plants. In addition, the exogenous ZmPHYA1 protein of about 170 kD was also checked by immuno-blot in three transgenic cotton lines. The results showed that the specific proteins could be detected in different tissues, including leaves, flowers and stems in the transgenic Line 9. The plant height of transgenic Line 9, Line 14, Line 41 were significantly shorter than that of the wild type, while the differences of other yield-related agronomic traits were not observed between the transgenic lines and the wild type. In this study, new cotton germplasms with glufosinate resistance and ZmPHYA1 gene were successfully obtained, which provided a material source for further utilization of phytochrome gene to innovate germplasm resources.