Table of Content

12 November 2021, Volume 47 Issue 11

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REVIEW

Research progress of crop diseases monitoring based on reflectance and chlorophyll fluorescence data

JING Xia, ZOU Qin, BAI Zong-Fan, HUANG Wen-Jiang

Acta Agronomica Sinica. 2021, 47(11):  2067-2079.  doi:10.3724/SP.J.1006.2021.03057

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Crop diseases are biological disasters that affect grain production and quality. The infestation of diseases consumes the nutrients and water, disrupts its normal life process, and causes changes in the internal physiological and biochemical state and external appearance of the crop. Canopy reflectance spectrum can detect crop population structure information well, and chlorophyll fluorescence data can sensitively reflect changes in crop photosynthetic physiology, both methods are capable of detecting crop diseases via remote sensing technology. This article outlined the current research status of crop diseases detection based on reflectance spectrum through remote sensing technology from the aspects of monitoring methods and monitoring scales, summarized the research progress of using active fluorescence, passive fluorescence and coordinated solar-induced chlorophyll fluorescence and reflectance spectroscopy to monitor crop diseases, analyzed the advantages and disadvantages of reflectance spectrum and chlorophyll fluorescence data in crop disease early warning detection, and discussed the possible problems in the remote sensing detection of crop diseases. On the basis, we made a prospect for the development of remote sensing monitoring crop diseases. This paper provides an important reference for the subsequent applications of crop diseases detection based on reflectance spectrum and chlorophyll fluorescence data.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Relationship between the allelic variations at the Ppo-A1 and Ppo-D1 loci and pre-harvest sprouting resistance in wheat

HUANG Yi-Wen, DAI Xu-Ran, LIU Hong-Wei, YANG Li, MAI Chun-Yan, YU Li-Qiang, YU Guang-Jun, ZHANG Hong-Jun, LI Hong-Jie, ZHOU Yang

Acta Agronomica Sinica. 2021, 47(11):  2080-2090.  doi:10.3724/SP.J.1006.2021.01089

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Ppo-A1 and Ppo-D1 are the major genes that control the activity of polyphenol oxidase (PPO) in wheat. It has been reported that the activity of polyphenol oxidase affects pre-harvest sprouting (PHS) resistance, but the effect of different alleles/allelic combinations at the Ppo-A1 and Ppo-D1 loci on PHS resistance remains unclear. The current study was carried out to elucidate the effects based on the germination index obtained from 248 Chinese wheat cultivars in a three-year trial in combination with genotypic data at the Ppo-A1 and Ppo-D1 loci. Analysis of variation for the Ppo-A1 and Ppo-D1 loci showed that year, Ppo-A1 locus and Ppo-A1 × Ppo-D1 interaction had significant effects on germination index. At locus Ppo-A1, germination index of cultivars carrying the allele Ppo-A1b of low PPO activity was 5.22% lower than that carrying the allele Ppo-A1a of high PPO activity on average. In contrast, the cultivars carrying the allele Ppo-D1a of low PPO activity had higher germination index than that carrying the allele Ppo-D1b of high PPO activity at locus Ppo-D1, but no significant differences between two alleles. Among the four allelic combinations, the cultivars with the Ppo-A1bPpo-D1b had the lowest germination index. The relationship between the alleles at locus Ppo-A1 and PHS resistance had been verified in the Lunxuan 13 × Jimai 20 F₂ and F_2:3 segregation populations. There were significantly positive correlations between PPO activity / relative expression level of Ppo-A1 gene and germination index. This study suggests that functional markers of allele Ppo-A1b can be effectively applied in marker-assisted selection for PHS resistance.

Molecular identification and breeding application of allelic variation of grain weight gene in wheat from the Yellow-Huai-River Valley

ZHANG Fu-Yan, CHENG Zhong-Jie, CHEN Xiao-Jie, WANG Jia-Huan, CHEN Feng, FAN Jia-Lin, ZHANG Jian-Wei, YANG Bao-An

Acta Agronomica Sinica. 2021, 47(11):  2091-2098.  doi:10.3724/SP.J.1006.2021.01083

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Grain weight is one of the most important yield traits in wheat. To accelerate the application process of dominant allelic variation of grain weight gene in wheat breeding, the allelic variation of grain weight gene was identified by using functional markers and the combinations of dominant grain weight genotypes were investigated the allelic variations of grain weight genes TaCwi-A1, TaGw8-B1, and TaGS-D1 in 183 wheat varieties (lines) from the Yellow-Huai-River Valley were identified by PCR amplification with specific primers. To identify the dominant genotype combinations, the effects of different allelic variation genotypes on wheat grain weight were studied by combining the phenotypic data of the 1000-grain weight (TGW) from 2016-2017 and 2017-2018. The results showed that the difference of TGW between different years was highly significant at P < 0.01. Two alleles, TaCwi-A1a and TaCwi-A1b, were detected at TaCwi-A1 locus, with the frequencies of 66.7% and 33.3%, respectively. The frequency of TaGw8-B1a allele on TaGw8-B1 locus was up to 94.5%, while the frequency of TaGw8-B1b allele was only 5.5%. In addition, two alleles, TaGS-D1a and TaGS-D1b, were found in TaGS-D1 locus, and their frequencies were 79.8% and 20.2%, respectively. Further results indicated that there were significant differences in TGW among different allelic variation combinations at P < 0.05. Among them, the average TGW of varieties with TaCwi-A1a/TaGS-D1a/TaGw8-B1a genotype was the highest. There was not significant difference in TGW between TaCwi-A1a/TaGS-D1a/TaGw8-B1a and TaCwi-A1b/ TaGS-D1a/TaGw8-B1a genotype, but it was significantly higher than other genotypes at P < 0.05. The average TGW of TaCwi-A1a/TaGS-D1a/TaGw8-B1b genotype was the lowest. The allelic variations at the loci of TaCwi-A1, TaGw8-B1, and TaGS-D1 all led to significant changes in TGW, and the allelic variations of TaGw8-B1 and TaGS-D1 loci were more important to TGW in wheat. There were no varieties with three low TGW allelic variation combinations TaCwi-A1b/TaGS-D1b/TaGw8-B1b in the tested materials. Among the seven different allele combinations, the average TGW of three high TGW allelic variation combinations TaCwi-A1a/TaGS-D1a/TaGw8-B1a was the highest, which was the dominant genotype combination.

Genome-wide association study of seed density and its related traits in Brassica napus L.

LEI Wei, WANG Rui-Li, WANG Liu-Yan, YUAN Fang, MENG Li-Jiao, XING Ming-Li, XU Lu, TANG Zhang-Lin, LI Jia-Na, CUI Cui, ZHOU Qing-Yuan

Acta Agronomica Sinica. 2021, 47(11):  2099-2110.  doi:10.3724/SP.J.1006.2021.04245

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Seed density reflects the accumulation characteristics of crop photosynthetic products in the grains, which plays an important role in the thousand-seed weight of rape. Selecting high seed density germplasm resources and studying the genetic characteristics of seed density are very important in the breeding of rapeseed. A natural population containing 187 Brassica napus L. varieties (lines) with different genetic backgrounds was used as plant materials to determine the seed density and its related traits (thousand-seed weight and seed volume) in the two environments. Genome-wide association study was carried out based on the optimal model and the candidate genes associated with seed density, thousand-seed weight, and seed volume was predicted. In the two years, there were significant differences in the seed density and its related traits among 187 materials at P < 0.05, and three materials with high seed density or thousand-seed weight were selected. A total of 24 SNP loci, that were significantly associated with seed density, seed weight, and seed volume, were identified by GWAS, which explained the phenotypic variation of 8.21%-10.40%. Haplotype analysis was used to determine the block interval of the SNP sites. The blocks containing 11 SNPs covered 12 candidate genes, which mainly encoded transcription factors such as WOX8, HAIKU1, AP2/ERF transcription factors, Dof family-zinc finger superfamily, BZR1 transcription factors, enzymes such as BKI1, KAT2, CEL1, UBP15, DNA binding proteins, and hormone response proteins such as ARF2 and J3. These results provide the theoretical basis for the development of high seed density rape varieties and the functional research of subsequent genes.

Effects of P_SAG12-IPT gene expression on leaf senescence, yield, and fiber quality in cotton

WANG Ye, LIU Zhao, XIAO Shuang, LI Fang-Jun, WU Xia, WANG Bao-Min, TIAN Xiao-Li

Acta Agronomica Sinica. 2021, 47(11):  2111-2120.  doi:10.3724/SP.J.1006.2021.04251

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A chimeric gene of bacterial IPT and the senescence-specific SAG12 promoter from Arabidopsis (P_SAG12-IPT) was overexpressed in cotton, and nine independent transgenic lines were obtained. To identify the leaf senescence characteristics, yield, and fiber quality of P_SAG12-IPT cotton plants, we performed the experiments at the Shangzhuang Experimental Station of China Agricultural University in 2011 and 2012. The results showed that the expression of IPT genes in transgenic lines was dramatically up-regulated at leaf aging stage, and the content of Z+ZR-type cytokinin was significantly higher than that of wild type Jihe 321. According to the content of Z+ZR-type cytokinin, nine transgenic lines were clustered into three categories with strong, weak, and moderate anti-aging ability. During leaf senescence period, the contents of chlorophyll and soluble proteins in transgenic lines were positively related to the content of Z+ZR-type cytokinin. Compared to wild type, transgenic lines had a higher or equal number of bolls (diameter ≥ 2 cm) per plant and boll weigh, but their boll-opening rate at the first harvest was significantly decreased, and the extent of reduction was positively related to the anti-aging ability. Consequently, the seed cotton yield of P_SAG12-IPT lines (OE-37 and OE-38) with strong or moderate anti-aging ability decreased due to less opened bolls, while the line (OE-30) with weak anti-aging ability had a comparable yield to that of wild type. The fiber length uniformity of P_SAG12-IPT cotton lines was significantly higher than that of wild type. Compared with wild type, the micronaire results of transgenic lines revealed an increasing trend, and fiber length, breaking strength, and breaking elongation was not significantly different from that of wild type.

Utilization of dynamic transcriptomics analysis for candidate gene mining of 100-seed weight in soybean

ZENG Jian, XU Xian-Chao, XU Yu-Fei, WANG Xiu-Cheng, YU Hai-Yan, FENG Bei-Bei, XING Guang-Nan

Acta Agronomica Sinica. 2021, 47(11):  2121-2133.  doi:10.3724/SP.J.1006.2021.04249

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100-seed weight of soybean is an important agronomic trait that affects yield, and it is of great significance to reveal its molecular basis and discover key candidate genes for soybean improvement breeding. In this study, weighted gene co-expression network analysis (WGCNA) was performed on the transcriptome data of 36 samples from 12 soybean varieties at three stages of seed development, and 20 gene co-expression modules were obtained. After correlating with 100-seed weight and four-seed shape traits, the green module was found to be most correlated with the phenotypes. Then 13 hub genes of green module were screened based on the Gene Significance (GS) and Eigengene Connectivity (kME) value. Gene differential expression of two groups of soybean varieties with extremely significant differences in 100-seed weight showed that the MAPK signaling pathway in the early and mid-term of seed development might regulate the 100-seed weight in soybean. According to SNPs/InDels calling and Gene Ontology (GO) annotation, Glyma.14G043900 and Glyma.15G217400 in the green module caused synonymous and non-synonymous coding mutations due to SNP mutations, and there were GO Terms and zinc finger domains related to gene expression regulation. These results suggested that they might regulate the 100-seed weight and seed shape of soybeans by regulating the hub gene and differentially expressed genes. Furthermore, Glyma.15G217400 was located in four reported QTLs of 100-seed weight, while Glyma.14G043900 was located in a reported seed protein content QTL and an oil content QTL. Compared with soybean public database, the increasing 100-seed weight alleles of the two genes were artificially selected and their frequency was gradually increased from wild accessions to landraces, resulting in the improved cultivars. These results provide new ideas for further discovering 100-seed weight candidate gene in soybean and its expression regulation mechanism.

Construction of yeast two-hybrid cDNA library induced by Ralstonia solanacearum and interaction protein screening for AhRRS5 in peanut

CHEN Yu-Ting, LIU Lu, CHU Pan-Pan, WEI Jia-Xian, QIAN Hui-Na, CHEN Hua, CAI Tie-Cheng, ZHUANG Wei-Jian, ZHANG Chong

Acta Agronomica Sinica. 2021, 47(11):  2134-2146.  doi:10.3724/SP.J.1006.2021.04254

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The overexpression of peanut AhRRS5 gene can significantly improve tobacco resistance to bacterial wilt in previous studies. To further explore signaling pathway of the NBS-LRR resistance protein AhRRS5 responding to Ralstonia solanacearum infection in peanut, the interaction proteins of AhRRS5 were screened by yeast two hybrid technology based on the construction of peanut root normalized three-frame libraries induced by Ralstonia solanacearum. Total RNA was extracted from peanut roots at different time points after Ralstonia solanacearum infection. The mRNA was isolated and purified, then double stranded cDNA was synthesized and normalized. The primary and secondary libraries were constructed by homologous recombination method. The titer of the secondary library was 1.44 × 10 ⁷ cfu mL^-1, the recombination rate was 100%, and the average length encoded by the inserted cDNA was more than 1000 bp. The bait vector pGBKT7-AhRRS5 was constructed by enzyme digestion and ligation method. Result showed that there was no toxicity and auto-activation in the yeast cells. The AD library plasmid and bait vector pGBKT7-AhRRS5 were co-transformed into yeast Y2H gold strain. After several screening and rotation verification, 12 candidate proteins were obtained, which were involved in plant growth and development, energy metabolism, hormone signal transduction, stress response and so on. The interaction of AhRRS5 with AhSBT1.6 was further confirmed by bimolecular fluorescence complementation assays (BiFC) in vivo. The relative expression levels of AhSBT1.6 genes revealed that there were significant differences in different tissues based on transcriptome profiling, indicating the potential involvement of AhSBT1.6 in regulating bacterial with resistance in peanut. This study lays a foundation for further study on the mechanism of NBS-LRR resistance protein AhRRS5 and its interaction protein in bacterial wilt resistance defense of peanut.

Construction linkage maps and identification of quantitative trait loci associated with important agronomic traits in purple-fleshed sweetpotato

MA Meng, YAN Hui, GAO Run-Fei, KOU Meng, TANG Wei, WANG Xin, ZHANG Yun-Gang, LI Qiang

Acta Agronomica Sinica. 2021, 47(11):  2147-2162.  doi:10.3724/SP.J.1006.2021.04271

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Ideal agronomic traits are the important objectives in sweetpotato breeding, but the breeding methods are still lacking. We constructed linkage maps using a mapping population of 274 individuals derived from a cross between the female parent Xuzishu 8 (a purple-fleshed cultivar with many branches, medium vine, and high yield) and the male parent Meiguohong (a white-fleshed cultivar with few branches, long vine, and medium yield) by simple sequence repeats (SSR) markers in this study. The female parent map contained 24 linkage groups, and covered 1325.8 cM with an average marker interval of 9.2 cM. The male parent map contained 21 linkage groups, and covered 1088.6 cM with an average marker interval of 8.2 cM. The maps could increase the density of existing genetic maps. Using the composite interval mapping, we analyzed five important agronomic traits, including branch number, vine diameter, longest vine length, petiole length, and internode length in sweetpotato, thus identified one QTL related to branch number explaining the phenotypic variance of 53.2%, one QTL related to internode diameter explaining the phenotypic variance of 16.7%, two QTLs related to longest vine length explaining the phenotypic variance of 9.5% and 13.7%, two QTLs related to petiole length explaining the phenotypic variance of 8.8% and 11.3%, and five QTLs related to internode length explaining the phenotypic variance of 9.6%-28.1%. The QTLs can be used to develop molecular markers and assist the screening of plants with ideal agronomic traits at early seedling stage, thus improved the efficiency of field selection.

Location and InDel markers for candidate interval of the orange petal gene in Brassica napus L. by next generation sequencing

GUO Qing-Qing, ZHOU Rong, CHEN Xue, CHEN Lei, LI Jia-Na, WANG Rui

Acta Agronomica Sinica. 2021, 47(11):  2163-2172.  doi:10.3724/SP.J.1006.2021.04236

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The petal color has been one of the major goals of breeding and genetic research in Brassica napus L. To date, there have been no reports about interval location of dominant orange petal gene trait in B. napus L. In this study, we constructed an F₂ mapping population with 458 individuals from the cross between DH Y05 (yellow petal) and DH R08 (orange petal). Whole-genome re-sequencing of DNAs and transcriptome sequencing of RNAs were from two populations each composed of 30 individuals showing extreme opposite trait for a given phenotype in a segregating progeny. Then we performed 30× and 6G of sequencing. Darmor-bzh as the reference genome was aligned to sequence data from the two bulks and parents. QTL-seq and Mutation Mapping Analysis Pipeline for Pooled RNA-seq (MMAPPR) workflow were applied to identify the candidate region of the orange petal gene. The insertion-deletion (InDel) sites can be visualized in candidate interval by Integrative Genomics Viewer (IGV). Based on these Indel variations, we used Vector and Blast to design InDel primers. The results indicated that the orange petal trait was controlled by a dominant major gene. A major candidate region was identified on chromosome A07 (18-19 Mb) of Darmor-bzh. Three InDel markers linked to the orange petal gene were screened by Polyacrylamide gel electrophoresis (PAGE). This study may provide a novel idea for fine mapping dominant orange petal gene as well as marker assisted selection.

Creation and combining ability analysis of recessive genic sterile lines with a new ptc1 locus in rice

LI Jing-Lin, LI Jia-Lin, LI Xin-Peng, AN Bao-Guang, ZENG Xiang, WU Yong-Zhong, HUANG Pei-Jing, LONG Tuan

Acta Agronomica Sinica. 2021, 47(11):  2173-2183.  doi:10.3724/SP.J.1006.2021.02076

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Cytoplasmic male sterile (CMS) lines and photoperiod/thermo-sensitive genic male sterile (PTGMS) lines are widely used as female parents in the commercial production of rice hybrid seeds. however, both systems have their intrinsic defects such as low usage of germplasm resources and unstable sterility. Recessive genic male sterile (GMS) lines, which overcome the problems of CMS and PTGMS lines, have played a key role in the development of next generation technologies for rice hybrid seed production. In this study, a GMS mutant ptc1-2 without pollen grains was identified from an irradiation-induced mutant library of 9311. Using a map-based cloning approach, a 257.37 kb deletion region was detected, which contained entire coding region of PTC1 on chromosome 9. PCR co-segregation analysis showed that the male sterility was completely associated with the ptc1-2 deletion region. The ptc1-2 deletion locus was then introgressed into a PTGMS line C815S and a CMS maintainer line Wufeng B by marker-assisted backcrossing. Corresponding GMS lines C815G and Wufeng G were obtained at BC₃F₃ generation, which showed the phenotypical similarity to the C815S and Wufeng B lines, respectively. Combining ability tests revealed that C815G and Wufeng G had the same combining ability as C815S and the CMS line Wufeng A in conventional field, respectively. These results indicated that ptc1-2 was a new allele of PTC1, which could be applied for breeding GMS lines and be the potential of GMS lines in rice hybrid seed production.

Identification and analysis of non-specific lipid transfer protein family in tobacco

LI Peng, LIU Che, SONG Hao, YAO Pan-Pan, SU Pei-Lin, WEI Yao-Wei, YANG Yong-Xia, LI Qing-Chang

Acta Agronomica Sinica. 2021, 47(11):  2184-2198.  doi:10.3724/SP.J.1006.2021.04240

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Plant non-specific lipid transfer proteins (nsLTPs) can transfer lipids in vitro, regulate plant growth and development, and respond to environmental abiotic and biotic stresses. In this study, 74 nsLTPs genes were identified from the genome of Nicotiana tabacum variety K326, and we analyzed multiple characteristics of these genes, including phylogeny, gene structures, conserved motifs, protein domains, chromosome locations, cis-elements in the promoter sequences, 3D structure, and the expression patterns under different hormones and abiotic stresses. The results revealed that nsLTPs in tobacco could be divided into eight types, including type I, II, III, IV, V, VII, VIII, and XIII, according to the interval and sequence similarity between the eight cysteines. The same types of NtLTPs had similar intron-exon patterns and conserved motifs, motif 2 and motif 3 were the characteristic motifs of NtLTPs family. In the process of evolution, fragment duplication dominated the expansion of the NtLTPs family. RNA-seq analysis after drought treatment revealed that the functional differentiation patterns of repeat gene pairs were diverse during evolution period. Promoter analysis showed that they contained a variety of cis-acting elements in response to light response, hormones, and abiotic stress. Furthermore, qRT-PCR demonstrated that NtLTPs family genes had different expression patterns in different tissues and organs of tobacco plants, which could respond to abiotic stresses such as drought, salt, and hormone treatments (IAA, GA, and SA etc.). These results provide a theoretical reference for the in-depth analysis of the functions of NtLTPs family genes and molecular breeding.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

An growing-period indicator of maize cultivars for mechanical kernel harvest

LI Lu-Lu, MING Bo, CHU Zhen-Dong, ZHANG Wan-Xu, GAO Shang, WANG Yi-Zhou, HOU Liang-Yu, ZHOU Xian-Lin, XIE Rui-Zhi, WANG Ke-Ru, HOU Peng, LI Shao-Kun

Acta Agronomica Sinica. 2021, 47(11):  2199-2207.  doi:10.3724/SP.J.1006.2021.03049

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The high kernel moisture of maize (Zea mays L.) at harvest stage limits the field-application of mechanical kernel harvesting. The breeding and selection of fast dry-down cultivars is the key to solve this problem. However, there is still a lack of such indicators for evaluating the kernel dry-down rate in China. To explore the indicators, the crop growth and the kernel dry-down of two cultivars, Xianyu 335 and Zhengdan 958, were investigated across various maize belts in China from 2014 to 2018. Between the two cultivars, there were significant varietal differences in thermal times (TT) at the stages of planting-maturity (P-M), planting-25% moisture (P-25%), and maturity-25% moisture (M-25%), respectively. The TT_P-M on average were 3039°C d (2752-3249°C d) for Xianyu 335 and 3090°C d (2750-3546°C d) for Zhengdan 958, with a difference value of 51°C d, and the corresponding coefficient of variations (CV) of TT_P-M were 4% and 6%, respectively. The TT_P-25% on average was 3097°C d (2920-3392°C d) for Xianyu 335 and 3309°C d (2980-3613°C d) for Zhengdan 958, with a larger difference value of 212°C d, while their CV were 4% and 5%. In several, the TT_M-25% for Xianyu 335 and Zhengdan 958 were 66°C d (0-287°C d) and 166°C d (36-338°C d) with the CV of 131% and 54%. On account of its better reflection of kernel dry-down rate among cultivars, the TT_P-25% could be considered as the growing period indicator for the breeding and selection of cultivars fitting to present mechanical kernel harvesting. In addition, this indicator might vary with region, year, or planting date, the same field and year were recommended to ensure a consistent environmental condition for measuring it. Conclusively, a new indicator (TT_P-25%) for breeding and selection of fast dry-down hybrids was proposed, which potentially prompting maize kernel harvesting in China.

Effects of ridge-and-furrow rainwater harvesting with mulching on soil water- heat-fertility and potato yield in arid areas of southern Ningxia

WU Chun-Hua, PU Xue-Ke, ZHOU Yong-Jin, MIAN You-Ming, MIAO Fang-Fang, LI Rong

Acta Agronomica Sinica. 2021, 47(11):  2208-2219.  doi:10.3724/SP.J.1006.2021.94194

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In order to explore the effect of different ridge-and-furrow rainwater harvesting with mulching patterns on soil water-heat-fertility properties and the yield of rainfed potato. A located experiment was conducted in 2015 and 2016 for two consecutive years, and six ridge-and-furrow rainwater harvesting with mulching patterns were set up in dry farmland of southern Ningxia. Ridges were mulched with plastic film, while furrows were covered with plastic film (PP), maize straw (PS), biodegradable film (PB), bast fiber film (PF), liquid film (PL), and furrow without mulching (PN), and the flat planting without mulching was used as control check (CK). We investigated the effect of ridge-and-furrow rainwater harvesting with mulching on soil water, temperature, nutrients, and potato yield. Furrow-and-ridge rainwater harvesting with mulching patterns could significantly increase average soil water storage in 0-200 cm layer during the whole growth period, and PS treatment had the best effect on soil water conservation. Compared with CK, PP treatment significantly increased topsoil temperature (0-25 cm) during the growth period, while PS treatment significantly reduced topsoil temperature in potato. Compared with the treatment before the experiment, the contents of soil organic carbon, total nitrogen, alkali-hydrolysed nitrogen, and available phosphorus in 0-40 cm layer under different furrow-and-ridge rainwater harvesting with mulching patterns were significantly increased, while the soil available potassium contents were significantly decreased during the two-year experiments. Compared with the control, the soil nutrients with different furrow-and-ridge rainwater harvesting with mulching patterns were significantly increased with the largest increase in soil nutrients in PS treatment. Ridge-and-furrow rainwater harvesting with mulching patterns could significantly improve potato yield and marketable tuber rate, and PS and PP treatments were the highest, followed by PB, PF, and PL treatments, while there was no significant difference between PN and CK treatments. According to correlation and path analysis, the soil water, organic carbon, and temperature were the important factors limiting the high yield of potato. The ridge mulched with plastic film and furrow covered with straw could significantly increase potato yield by improving the soil water, temperature, and nutrient environment in dryland. It had certain application value in high yield cultivation of potato in arid areas of southern Ningxia.

Effects of elevated temperature and CO₂ concentration on growth and yield of maize under intercropping with peanut

WANG Fei, GUO Bin-Bin, SUN Zeng-Guang, YIN Fei, LIU Ling, JIAO Nian-Yuan, FU Guo-Zhan

Acta Agronomica Sinica. 2021, 47(11):  2220-2231.  doi:10.3724/SP.J.1006.2021.03018

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To clarify the effects of climate change on the growth development and yield of maize in the system of maize intercropping peanut, we performed the planting pattern of two rows maize intercropping and four rows peanut. Field experiments were carried out with TC (ambient temperature and ambient CO₂ concentration), +T+C (elevated temperature and elevated CO₂ concentration) in 2018, and TC, +TC (elevated temperature and ambient CO₂ concentration), and +T+C in 2019, with two phosphorus levels of P₀ (P₂O₅ 0 kg hm^-2) and P₁₈₀ (P₂O₅ 180 kg hm^-2), respectively. The effects of elevated temperature and CO₂ concentration on growth, dry matter accumulation and distribution, photosynthesis and yield of intercropping maize were studied. Results were as follows: (1) Compared with TC, the numbers of days from emergence to silking, silking to maturity, and emergence to maturity of intercropping maize under +TC were shortened respective by 4, 2, and 6 days. Compared with +TC, the number of days from emergence to silking of intercropping maize under +T+C was shortened by three days, while the numbers of days from silking to maturity, and emergence to maturity were increased by five days and two days. Compared with TC, the number of days from emergence to silking, and emergence to maturity of intercropping maize under +T+C was shortened by 4-7 days and 2-4 days, respectively; and the number of days from emergence to maturity was extended by 1-4 days. (2) The leaf area, net photosynthetic rate, and leaf area duration of intercropping maize were +T+C>+TC>TC before silking, +T+C>TC>+TC from silking to milk stage, and +T >+T+C>+TC after milk stage. Compared with TC, ear grain number and 100-grain weight of intercropping maize under +T+C were increased by 4.14%-65.70% and 1.70%-14.0%, respectively. (3) Compared with TC, the dry matter of intercropping maize at maturity stage increased by 7.39%-21.30% and the yield increased by 19.18%-28.07% under +TC. The dry matter and yield of intercropping maize increased by 10.0%-57.7% and 4.41%-52.00% under +T+C, respectively. The grain yield of intercropping maize was improved by applying phosphorus after increasing temperature and CO₂ concentration. These results indicated that elevated temperature and CO₂ concentration could promote dry matter accumulation and grain yield improvement by increasing net photosynthetic rate, leaf area index, and leaf area duration of intercropping maize at early growth stage, shortening vegetative growth period, prolonging grain filling time, and increasing ear grain number and grain weight per panicle. Elevated temperature and CO₂ concentration had mutual promoting effect on the growth of intercropping maize before silking stage, while increasing CO₂ concentration could make up for the inhibiting effect of increasing temperature on the growth of intercropping maize after silking.

Effects of side deep placement of nitrogen on rice yield and nitrogen use efficiency

HUANG Heng, JIANG Heng-Xin, LIU Guang-Ming, YUAN Jia-Qi, WANG Yuan, ZHAO Can, WANG Wei-Ling, HUO Zhong-Yang, XU Ke, DAI Qi-Gen, ZHANG Hong-Cheng, LI De-Jian, LIU Guo-Lin

Acta Agronomica Sinica. 2021, 47(11):  2232-2249.  doi:10.3724/SP.J.1006.2021.02086

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Lateral deep fertilization is an efficient, high-quality, and safe cultivation technology of rice mechanical transplanting. In order to improve the technical system of lateral deep fertilization, we investigated the effects of different fertilization methods on rice yield and nitrogen use efficiency under the condition of lateral deep fertilization. In this study, Nanjing 9108 and Nanjing 5718, the representative varieties of quality and delicious rice of Jiangsu, were used as materials. Four different lateral deep fertilization methods were arranged, including 100% base fertilizer side deep application FM1 (fertilization method 1), 70% base fertilizer side deep application + 30% tillering fertilizer FM2 (fertilization method 2), 70% base fertilizer side deep application + 30% panicle fertilizer FM3 (fertilization method 3), and 35% base fertilizer side deep application + 35% tillering fertilizer + 30% panicle fertilizer FM4 (fertilization method 4). In addition, the conventional fertilization method and no nitrogen treatment were added. The effects of different treatments on rice yield, leaf area index, photosynthetic potential, dry matter accumulation, population growth rate, and nitrogen use efficiency were compared. The results revealed that the yield of FM3 and FM4 were higher than those of other treatments. The main reason was that the spikelet number of the population was significantly higher than that of other treatments on the basis of stable panicle number. The leaf area index and dry matter accumulation of FM3 treatment were higher in the middle and late growth stages, especially from heading to maturity stage. Nitrogen accumulation of FM3 was less before jointing stage, but nitrogen accumulation after jointing stage and the total nitrogen uptake during the whole growth period were significantly higher than those of other treatments. Moreover, the nitrogen agronomic utilization rate, nitrogen physiological utilization rate, nitrogen absorption utilization rate, and nitrogen partial productivity of FM3 were significantly higher than those of the other treatments. At the same time, compared with CFM and FM4, FM3 can reduce fertilization times by 1-2 times, save labor and cost, and is conducive to large-scale production. It is a high-yield, simple and efficient fertilization method for rice.

Adaption of rice-wheat cropping system to climate warming in Jianghuai area

CHEN Chang-Qing, LI Wei-Wei, ZHU Xiang-Cheng, LIU Jing, LI Gang-Hua, XU Ke, JIANG Yu, DING Yan-Feng

Acta Agronomica Sinica. 2021, 47(11):  2250-2257.  doi:10.3724/SP.J.1006.2021.02078

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As the climate warming is increasing, the global average surface temperature has risen by nearly 1°C in the past 100 years. Rice-wheat cropping system is the mainstream cropping system in the lower reaches of the Yangtze River and Huaihe River in Jiangsu and Anhui provinces, but its adaptation to climate warming is still unclear. We analyzed the characteristics of temperature rise and crop phenological changes in the rice-wheat double cropping area of Jiangsu using the historical data from 34 meteorological stations and 45 phenological stations over the years. The results revealed that the range of temperature increase in Jianghuai area was higher in the south than in the north, higher in wheat season and lower in rice ripe season, and the highest in March. In the rice season, the sowing date in Jiangnan was delayed by 3.4 d 10a^-1, the heading date in Huainan was advanced by 2 d 10a^-1, and the harvest date in Huaibei was delayed by 6.2 d 10a^-1. In the wheat season, the sowing date in Jiangnan was delayed by 6.4 d 10a^-1, and the heading and harvest time tended to be earlier in the whole region. The rice-wheat stubble stage was shortened by 4.6 d 10a^-1 in Huaibei and 6.9 d 10a^-1 in Jiangnan. The average temperature of rice and wheat during growth period had no significant change, but the effective accumulated temperature post anthesis was increasing. There was no significant change of the production efficiency of accumulated temperature in rice season, while the production efficiency of accumulated temperature in wheat season increased by 0.008-0.346 kg hm^-2°C^-1 10a^-1. Warming decreased wheat yields in the north of Yangtze River and Huainan area, but increased wheat yield in Huaibei area. In summary, these results indicated that the rice-wheat cropping system in Jianghuai was gradually adapting to the climate warming, and the negative effects of climate warming on crop yield could be alleviated by reasonably changing sowing date. Our findings can provide reference for climate change adaptation cultivation and cultivation technology innovation.

Effects of applying potassium at different growth stages on dry matter accumulation and yield of winter wheat in different soil-texture fields

HU Xin-Hui, GU Shu-Bo, ZHU Jun-Ke, WANG Dong

Acta Agronomica Sinica. 2021, 47(11):  2258-2267.  doi:10.3724/SP.J.1006.2021.01081

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To investigate the effects of potassium applying on the grain yield formation of winter wheat, the experiments were carried out on different soil textures with high-yield winter wheat variety Taimai 198. To analyze the effects of potassium application at different stages on winter wheat flag leaf photosynthetic characteristics, dry matter accumulation and distribution, and grain yield under different soil texture conditions, two soil texture test fields [sandy loam (S) and silty loam (F)] and three treatments [no potassium fertilizer (K0), potassium fertilizer base application (100% applicating at sowing, K1), and split application (50% applicating at sowing stage + 50% topdressing at the jointing stage, K2)] was arranged. The results showed that the interaction of soil texture and potassium application significantly affected the grain number per spike and dry matter assimilated after anthesis and grain yield. Under the two soil texture conditions, potassium application significantly increased the grain yield of winter wheat, and K2 treatment had the highest yield. Compared with K1 treatment, the grains number per ear, the SPAD and net photosynthetic rate of flag leaves after anthesis, the accumulation of dry matter per stem after anthesis, and the transfer of assimilation to the grain after anthesis were increased under K2 treatment. Under sandy loam conditions, grain yield of K2 treatment was by 12.4% and 10.4% higher than that of K1 treatment, respectively. Under silt loam conditions, grain yield was by 5.2% and 5.4% higher than that of K1 treatment. Those results indicated that wheat yield was significantly increased by changing potassium fertilizer base application to 50% base application with 50% topdressing at jointing stage, and the wheat yield was higher in sandy loam field.

Effects of maize and soybean intercropping on nodule growth, nitrogen fixation of soybean under low phosphorus condition

QIN Xiao-Min, PAN Hao-Nan, XIAO Jing-Xiu, TANG Li, ZHENG Yi

Acta Agronomica Sinica. 2021, 47(11):  2268-2277.  doi:10.3724/SP.J.1006.2021.04237

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To investigate the effects of maize and soybean intercropping on nitrogen and phosphorus uptake, nodule growth, and nitrogen fixation in soybean, a pot experiment was conducted with two phosphorus (P) rates (low P -P50 and sufficient P -P100). The results showed that, compared with monocropped soybean, intercropping of soybean and maize significantly increased the nodule number, nodule weight, leghemoglobin content, and nitrogenase activity of nodule, and promoted the growth and nitrogen (N) and phosphorus uptake of soybean under P50 and P100 rates. The concentrations of N, P, and the activities of acid phosphatase, phytase in nodules in intercropped soybean were significantly higher than those of monocropped soybean under P50 and P100 rates, and the activities of acid phosphatase and phytase showed the highest values under IS-P50 treatment. In addition, the P concentration in the nodules of intercropped soybean under P50 rate was significantly higher than that of monocropped soybean under P90 rate. so In summary, to maintain the larger phosphorus content for nitrogen fixation of soybean under phosphorus deficiency, the soybean and maize intercropping system increased the phosphorus concentration in the nodules mainly by enhancing the activities of acid phosphatase and phytase in the nodules, and thus promoted the growth and nitrogen uptake of soybean.

RESEARCH NOTES

Physiological characters of carbon, nitrogen, and hormones in ratooning rice cultivars with strong regeneration ability

HUANG Su-Hua, LIN Xi-Yue, LEI Zheng-Ping, DING Zai-Song, ZHAO Ming

Acta Agronomica Sinica. 2021, 47(11):  2278-2289.  doi:10.3724/SP.J.1006.2021.02070

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It is of great significance to clarify the physiological basis and hormone regulation characteristics of axillary bud germination for the selection of ratoon rice cultivars with strong ratooning ability and the regulation of cultivation techniques. In this study, the content of non-structural carbohydrate (NSC) and total nitrogen in different parts of 13 cultivars selected in 2019 were analyzed at the first harvest stage using the screening platform established in Chongyi County, Jiangxi Province. The biosynthesis and signal transduction genes of brassinolides and strigolactones, which promoted and inhibited axillary bud germination, were also studied. The results showed that there were significant differences in the regeneration rate of 13 cultivars, ranging from 1.26 to 2.38. The contents of soluble sugar, starch and non-structural carbohydrate in leaves, leaf sheaths, and stems were significantly different among different cultivars at different node positions (P-values were all less than 0.001). The total nitrogen content was also significant difference among them except for the upper and lower node stems. The correlation analysis showed that the contents of the soluble sugar, starch and NSC of the stem at the lower node had significant or extremely significant correlation with the regeneration rates (R² = 0.4442^*, 0.9000^**, and 0.8303^**, respectively), while there was no significant correlation in others. The relative expression levels of tillering promoting genes (CYP90A, CYP85A2, D2, BRI, BSK, and CYCD3) in BR synthesis and signal pathway were higher, while the inhibited tillering genes (CYP734A1, BZR, and BKI) were lower in Guyou 676 with higher regeneration rates. In conclusion, the starch content in the stem at the lower node could be used as the screening index of strong regeneration ability cultivar, and also the relative expression levels of BR pathway related genes could be used as supplementary indexes.

Evaluation of natural resistance to smut in elite sugarcane varieties (lines)

CANG Xiao-Yan, XIA Hong-Ming, LI Wen-Feng, WANG Xiao-Yan, SHAN Hong-Li, WANG Chang-Mi, LI Jie, ZHANG Rong-Yue, HUANG Ying-Kun

Acta Agronomica Sinica. 2021, 47(11):  2290-2296.  doi:10.3724/SP.J.1006.2021.04257

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Sugarcane smut is a systemic fungal disease that seriously affects the development of sugarcane industry in China. Different sugarcane varieties have various resistance to smut. Screening and planting resistant varieties are the most economical and effective measure to control smut disease. In order to determine the smut resistance of elite varieties (lines) bred in China in recent year and screen resistant varieties for application in production, the resistance of 100 Chinese elite sugarcane varieties (lines) were evaluated by artificial inoculation with the impregnation method in smut epidemic area Yuanjiang, Yunnan Province. The results revealed that 56 of the 100 elite varieties (lines) were highly resistant to moderately resistant, accounting for 56%, and 44 were moderately susceptible to highly susceptible 2, accounting for 44%. The results showed that current large-scale planted and promoted varieties (lines) Mintang 69-421, ROC 22, Liucheng 03-182, Liucheng 03-1137, Guitang 42, Yuegan 26, Guitang 02-351, and Yunzhe 09-1601 were highly susceptible. And the sugarcane varieties (lines) bred in recent years, Funong 15, Funong 36, Funong 1110, Funong 07-3206, Funong 11-2907, Mintang 11-610, Yuegan 39, Yuegan 43, Yuegan 48, Yuegan 49, Yuegan 50, Yuetang 00-236, Ganzhe 02-70, Yunzhe 99-596, Yunzhe 03-258, Yunzhe 04-241, Yunzhe 06-80, Yunzhe 07-2800, Yunzhe 08-2060, Yunzhe 10-2698, Yunzhe 13-1139, Yunrui 10-701, Dezhe 09-84, Dezhe 12-88, Guitang 08-1589, and Zhongzhe 1 were highly resistant to smut disease. It was suggested that in the high incidence area of sugarcane smut in low altitude valley, efforts should be carried out to eliminate the elite varieties susceptible to the disease and popularize and apply the superior varieties resistant to the disease in order to achieve the rational distribution of varieties, control the outbreak and epidemic of sugarcane smut, and provide guarantee for the high-quality development of sugarcane industry.