Table of Content

12 February 2021, Volume 47 Issue 2

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REVIEW

Research advance on calcium content in wheat grains

LIU Yu-Xiu, HUANG Shu-Hua, WANG Jing-Lin, ZHANG Zheng-Mao

Acta Agronomica Sinica. 2021, 47(2):  187-196.  doi:10.3724/SP.J.1006.2021.01045

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Increasing the mineral content is becoming the important research direction and major target for crops breeding in the world. Calcium is an essential mineral element for human health and plays a pivotal role in skeletogenesis and metabolism. It is estimated that about 3.5 billion people was suffered from calcium deficiencies. Calcium deficiency has become a major international problem harming human health. The staple food is an optimal and safe way to mineral supplement. Wheat, one of the main food crops in China and even in the world, is the main source of food for 35%-40% of global population, a main source for human’s calcium intake as well as an important crop of mineral element biofortification. Improving the calcium content in wheat grains through genetic improvement is considered to be the most economical, effective and sustainable measure to solve the calcium deficiency, which has aroused great concern from international scholars. This paper summarized the recent advances in the study of calcium content in wheat grains, mainly including the genetic variation, affecting factors, the relationship with related traits and regulation mechanism of calcium content in grain. Furthermore, we also put forward the direction of future research on calcium-fortified wheat, which provides solutions for accelerating the effective calcium supplementation through staple food, promoting the healthy and nutritious dietary pattern, ensuring the food security to meet the transition from “quantitative” to “qualitative” demands, improving people’s health, and reducing economic losses caused by calcium deficiency.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Effect of OsPAL2;3 in regulation of rice allopathic inhibition on barnyardgrass (Echinochloa crusgalli L.)

LI Lan-Lan, MU Dan, YAN Xue, YANG Lu-Ke, LIN Wen-Xiong, FANG Chang-Xun

Acta Agronomica Sinica. 2021, 47(2):  197-209.  doi:10.3724/SP.J.1006.2021.02034

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Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) is the key enzyme in regulation of the synthesis of phenolic acid allelochemicals. PAL gene in rice belongs to a multigene family. In allelopathic accession rice PI312777 and non-allelopathic rice accession Lemont, the promoter sequences of the same PAL gene member were different, and there was the largest difference in OsPAL2;3 and OsPAL2;4 gene promoter sequence. Gene promoter of OsPAL2;3 from PI3127777 showed higher activity than the corresponding promoter from Lemont. Overexpression of OsPAL2;3 in PI312777 and Lemont resulted in increasing allelopathic inhibition on barnyardgrass (Echinochloa crusgalli L.), and the inhibitory ratios was increased by 11.11% in PI312777 and 5.56% in Lemont. Gene expression level of OsPAL2;3, OsC4H, OsCCA, OsCOL, and OsOMT was up-regulated in the OsPAL2;3-overexpressed transgenic rice compared with that of wild-type rice, and the contents of protocatechuic acid and vanillic acid were also increased. The results from Co-IP combined with mass spectrometry showed that transketolase, carbonic anhydrase, fructose-bisphospate aldolase isozyme, ATP synthase subunit alpha and ATP synthase subunit beta were interacted with OsPAL2;3 protein, resulting in regulating the phenylalanine pathway in rice. Our study indicated that the transcriptional activity of OsPAL2;3 contributed to the alleloapthic activity between PI312777 and Lemont, OsPAL2;3 was interacted with a couple of proteins to jointly regulate the synthesis of phenolic acids, and OsPAL2;3 could be considered as a candidate gene to improve the allelopathy of rice in breeding.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Breeding of a novel clubroot disease-resistant Brassica napus variety Huayouza 62R

LI Qian, Nadil Shah, ZHOU Yuan-Wei, HOU Zhao-Ke, GONG Jian-Fang, LIU Jue, SHANG Zheng-Wei, ZHANG Lei, ZHAN Zong-Xiang, CHANG Hai-Bin, FU Ting-Dong, PIAO Zhong-Yun, ZHANG Chun-Yu

Acta Agronomica Sinica. 2021, 47(2):  210-223.  doi:10.3724/SP.J.1006.2021.04086

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The rapeseed clubroot disease incidence in China is about 0.67 million hectare, accounting for 10% of the canola production area, which become a serious threat for the safety of Brassica napus industry. Based on this, we used CR Shinki, a Chinese cabbage material containing CRb clubroot disease resistance locus, as the donor parent, and Pol.CMS restorer line Bing409, the parent of Brassica napus national approved varieties Huayouza 62, as the recipient parent, and the CRb resistance locus was introduced into Bing409 by breeding programs such as crossing, backcrossing, self-cross with the foreground and genetic background selection. In the BC₃F₂ generation, a new restorer line Bing409R with a genetic background close to Bing409 containing CRb resistance locus was obtained, and Huayouza 62R, the first rapeseed hybrid resistant to clubroot disease in China was successfully developed. The results were as follows: CRb disease resistance locus appeared as a dominant single-gene inheritance in B. napus background, and the genetic improvement of resistance to clubroot disease did not at the expense of yield and quality losses for new restorer line Bing409R and its hybrid Huayouza 62R. Bing409R and Huayouza 62R were showed immune-resistance to physiological races of Plasmodiophora brassicae in Sichuan, Hubei, and Anhui provinces in China. This study will provide valuable resources for the breeding of rapeseed in China, and supplemented important support to overcome the threat of rapeseed clubroot disease.

TaPP2-A13 gene shows induced expression pattern in wheat responses to stresses and interacts with adaptor protein SKP1 from SCF complex

MENG Yu-Yu, WEI Chun-Ru, FAN Run-Qiao, YU Xiu-Mei, WANG Xiao-Dong, ZHAO Wei-Quan, WEI Xin-Yan, KANG Zhen-Sheng, LIU Da-Qun

Acta Agronomica Sinica. 2021, 47(2):  224-236.  doi:10.3724/SP.J.1006.2021.01042

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To explore the function and molecular mechanism of Phloem protein 2 (PP2) gene in wheat (Triticum aestivum L.) response to stresses, a TaPP2-A13 putatively encoding a PP2 protein was obtained from TcLr15, a wheat near isogenic line against leaf rust pathogen, in the present study. The complete coding region of TaPP2-A13 encodes a hydrophilic polypeptide with molecular weight of 33.18 kD, and theoretical isoelectric point is 6.36. There is an F-box domain at N-terminal and a PP2 domain at C-terminal of the TaPP2-A13 protein sequence, which indicates that wheat TaPP2-A13 belongs to F-box/PP2 (FBP) subfamily. Wheat TaPP2-A13 shared relatively higher sequence similarity with PP2-A13 from Gramineae. Quantitative real-time PCR (qRT-PCR) results indicated that TaPP2-A13 was induced by infection of leaf rust pathogen (Puccinia triticina), and showed stronger expression in susceptible combination than that in resistant one. An obvious up-regulation of TaPP2-A13 was observed after treatment with abscisic acid (ABA), salicylic acid (SA) and methyl jasmonate (MeJA) in wheat. TaPP2-A13 was significantly down-regulated after treatment with PEG and H₂O₂, while TaPP2-A13 striking increased first, then fell down after NaCl treatment in wheat. Subcellular localization result indicated that TaPP2-A13 distributed in both of the nucleus and cytoplasm. The recombinant vector BD-TaPP2-A13 was used as the bait to screen Yeast 2 Hybrid (Y2H) library, 11 kinds of proteins were finally obtained. Further Y2H assays identified that TaPP2-A13 physically interacted with five kinds of proteins including TaPP2C5, TaSLY1, TaCHI, TaRbcS, and TaSKP1. BiFC and Co-IP results further confirmed that TaPP2-A13 interacted with TaSKP1, an adaptor protein from SKP1-Cullin-F-box (SCF) complex, which made us to speculate that TaPP2-A13 functions as a member of SCF complex by binding with TaSKP1. These findings laid some foundation for further analyzing the function of TaPP2-A13 and exploring its regulatory network.

Distribution survey of soybean cyst nematode of new race X12 in Gujiao city, Shanxi province

LIAN Yun, WANG Jin-She, WEI He, LI Jin-Ying, GONG Gui-Ming, WANG Shu-Feng, ZHANG Jing-Peng, LI Mao-Lin, GUO Jian-Qiu, LU Wei-Quo

Acta Agronomica Sinica. 2021, 47(2):  237-244.  doi:10.3724/SP.J.1006.2021.04111

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X12 was a new race of soybean cyst nematode (SCN) with super strong pathogenicity and it was first detected in Xingjiashe county, Gujiao city, Shanxi province, China in 2012, which was a huge threat to soybean production. The research of race X12 distribution is meaningful for developing management strategies to prevent race X12 population from spreading. Therefore, a survey for the distribution of soybean cyst nematode race X12 in Gujiao city was conducted in 2019 and 2020. A distribution of races was constructed based on Riggs model. The race distribution was discussed in this study. A total of 33 soil samples infected soybean cyst nematode were collected. Twenty-six were identified as physiological subtypes, accounting for 78.8% of the samples, in which race 2 and race 4 accounted for 57.7% (15 samples) and 42.3% (11 samples), respectively. In general, race X12 was determined if race 4 population virulent on ZDD2315 accession with female index (FI) > 10. In 11 samples determined as race 4, including two samples were further determined as race X12 including the sample collected from Xingjiashe location, which was the original location detected as race X12 in 2012. There were three other SCN populations which determined as race 4 could virulent on ZDD2315 but with FI < 10. There were 73.1% and 57.7% of populations with FI > 50 among 26 evaluated populations on Peking and PI88788, respectively. The results showed that race X12 population were also detected in Hekouzhen except Xingjiashe. Only race 2 and race 4 were detected around Xingjiashe, covered 810 km². SCN populations with 3 samples were likely to preferentially evolve from subspecies 4 to subspecies X12. The results showed that strong and effective measures should be taken in Gujiao city to slow down the virulence escalation of SCN and the spread of X12 species.

Genome-wide association analysis for late blight resistance of potato resources

JIANG Wei, PAN Zhe-Chao, BAO Li-Xian, ZHOU Fu-Xian, LI Yan-Shan, SUI Qi-Jun, LI Xian-Ping

Acta Agronomica Sinica. 2021, 47(2):  245-261.  doi:10.3724/SP.J.1006.2021.04099

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The mining of broad-spectrum resistance genes is the basis of the breeding of potato varieties with high late blight resistance. In this study, 288 samples of late disease resistance selected by the International Potato Center (CIP) for years were planted and were investigated for two consecutive years, which could provide some theoretical and material basis for breeding of late blight resistant varieties and help to study on disease resistance mechanism. The late blight resistance of each sample was evaluated using AUDPC and sAUDPC values. The population simplified genome sequencing was performed by SLAF-seq and carried out by genome-wide association analysis in order to discover the genetic loci and candidate genes related to late blight resistance. There were wide genetic differences in resistance to late blight among 288 samples. Through genome-wide association analysis, based on five analytical models, a total of 82 loci significantly correlated with late blight resistance were identified. Combined with genomic annotation, there were 54 candidate genes known or likely to be associated with late blight resistance in the association interval. Among them, 23 genes were resistant genes, including late blight resistance gene R1 homolog, Sw-5 homolog (R8) and Rpi-vnt1, as well as gene encoding pleiotropic resistance protein. Five genes encoded MAPK protein and WRKY transcription factor; one gene was involved in the JA pathway; three genes were associated with salicylic acid pathway; six genes were related to the course of the disease; three genes were involved in the synthesis of phenylpropionic acid. Other genes related to resistance to late blight included HMGR gene (2) and cytochrome P450 (21).

Genome-wide association analysis reveals zinc-tolerant loci of rapeseed at germination stage

WEI Li-Juan, SHEN Shu-Lin, HUANG Xiao-Hu, MA Guo-Qiang, WANG Xi-Tong, YANG Yi-Ling, LI Huan-Dong, WANG Shu-Xian, ZHU Mei-Chen, TANG Zhang-Lin, LU Kun, LI Jia-Na, QU Cun-Min

Acta Agronomica Sinica. 2021, 47(2):  262-274.  doi:10.3724/SP.J.1006.2021.04037

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Zinc (Zn) is one of the important mircroelements, but the excessive amount application would affect plant growth and development. Genome-wide association analysis (GWAS) was performed on the relative hypocotyl length (RHL) using the 140 B. napus genotyped under zinc stress treatment (30 mg L^-1) at germination stage by Illumina 60K SNP array, and then significant SNP locus and candidate genes were detected. In the study, the population structure analysis revealed that the 140 B. napus were classified into two subgroups, and the kinship coefficients of the 89% materials were less than 0.1, indicating the tested population had a distant relationship. GWAS analysis indicated that there were significantly 8 SNP locus correlated to RHL, and single SNP loci could give an explanation on the 22.0%-33.2% phenotype variation. The differential expressed gene (DEGs) were detected by RNA-Seq. GO enrichment analysis indicated that the up-regulated genes mainly participated in redox reaction, ion transport, stress response, defense response and sulfur compound transport. Nineteen candidate genes response to zinc stress were identified by GWAS analysis and RNA-seq, including the genes encoding zinc finger protein (B-box type and ZFP1), glutathione transferase GSTU21, peroxidase family protein, ABC and MFS transporters, cell wall-related kinase protein, and genes encoding transcription factors (TF), such as BnaA07g27330D (MYB), BnaA02g30270D (bHLH), BnaA07g27840D (WRKY57), BnaA07g31860D (ORA47), and BnaA07g28000 (NAC). This study laid the foundation for understanding the molecular mechanism of zinc stress in B. napus.

Identification of resistance gene against phytophthora root rot in new soybean lines breeded in Henan province

ZHANG Xue-Cui, SUN Su-Li, LU Wei-Guo, LI Hai-Chao, JIA Yan-Yan, DUAN Can-Xing, ZHU Zhen-Dong

Acta Agronomica Sinica. 2021, 47(2):  275-284.  doi:10.3724/SP.J.1006.2021.04105

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Phytophthora root rot is one of the destructive diseases affecting soybean production, which is a great threat to soybean production. Planting resistant soybean cultivars is the most effective way to control this disease. Henan province was located in the hinterland area of the summer-sowing soybean production region of Huang-Huai in China, which had the potential threat region of phytophthora root rot. The objective of this study was to screen effective resistance cultivars for disease control and resistance breeding by phenotypic identification and molecular detection of resistance gene. Sixty-four new soybean lines bred in Henan were evaluated for their resistance responses to two Phytophthora sojae isolates PsJS2 and Ps41-1 using the hypocotyls inoculation technique. The result showed that 35 lines and 16 lines were resistance to Ps41-1 and PsJS2, respectively. Sixteen lines and 10 lines were intermediate to Ps41-1 and PsJS2, respectively. And there were 16 lines resistance to both Ps41-1and PsJS2, accounting for 25% of tested lines. Sixty-four lines was detected for Phytophthora resistance gene by using molecular marker WZInDel11 co-segregating with a resistance gene RpsZheng. The results showed that, 13 of 16 lines resistant to both PsJS2 and Ps41-1 contain target band of WZInDel11, while 5 lines resistant to one of two P. sojae isolates show segregating to P. sojae produced heterozygous bands. The homozygous resistant plants of these lines segregating for resistance could be accurately detected by marker WZInDel11, and further were directly developed into homozygous resistant lines. Combining the results of pedigree analysis, it was speculated that two lines might contain the resistance gene RpsZheng, two lines might contain RpsYD29, and 14 lines might contain RpsZheng or its allele. In conclusion, the results indicated that the new soybean lines cultivated in Henan Province had excellent resistance sources to P. sojae. This study provides important information for disease control and resistance breeding.

Phenotype analysis and gene mapping of small kernel 7 (smk7) mutant in maize

JIANG Cheng-Gong, SHI Hui-Min, WANG Hong-Wu, LI Kun, HUANG Chang-Ling, LIU Zhi-Fang, WU Yu-Jin, LI Shu-Qiang, HU Xiao-Jiao, MA Qing

Acta Agronomica Sinica. 2021, 47(2):  285-293.  doi:10.3724/SP.J.1006.2021.03015

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In this study, a stable small kernel mutant, named small kernel 7 (smk7), was isolated from ethylmethane sulfonate (EMS) mutagenesis of maize inbred line B73. Compared with wild type, the smk7 mutants showed smaller kernel size, defective embryo and endosperm development and a significant decrease in 100-kernel weight. The smk7 kernels showed a low level of germination rate at 10% and cannot grow into normal plants. No significant changes were detected in protein, starch and oil content between mature wild type and smk7 kernels, but the starch grains became significantly smaller and irregular in smk7 kernels compared with wild type. The smk7 kernels could be clearly distinguished from the wild type as early as 12 days after pollination (DAP), on the basis of their smaller and emptier phenotype. Microscopic inspection of the paraffin sections revealed that the development of embryo and endosperm were delayed, and the cell wall in growth in basal endosperm transfer layers (BETL) were arrested in smk7 compared with wild type. The F₂ populations with multiple backgrounds were constructed by crossing heterozygous plants (+/smk7) with several other inbred lines. Genetic analysis showed that the mutant phenotype was controlled by a single recessive gene. Based on genotyping by target sequencing (GBTS) strategy, the SMK7 was initially mapped on the short arm of chromosome 2. The fine mapping results suggested that SMK7 was located between markers RM1433917 and RM1535316, with a physical distance of 120 kb. There were eight protein-coding genes in this region. This study laid a foundation for further genes cloning and research of the SMK7 function in regulating maize kernel development.

Statistical analysis of randomized complete block design with repeated measure data using Generalized Linear Mixed Models (GLIMMIX)

ZHANG Jiu-Quan, YAN Hui-Feng, CHU Ji-Deng, LI Cai-Bin

Acta Agronomica Sinica. 2021, 47(2):  294-304.  doi:10.3724/SP.J.1006.2021.04085

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Multiple measurements of the same subject are conducted, and there is autocorrelations among the data at each time point. Some special treatment is required for statistical analysis of repeated measure data. Although the repeated measure is widely used in agricultural and other research fields, the relevant and effective statistical methods are rare. In order to establish a simple, easy to use, and reliable statistical method, generalized linear mixed models (GLIMMIX) of SAS was adapted. Selection of covariance structure, variance analysis, and means comparison processes were showed by using RCB data. Traditional split plot and MANOVA methods wasted large amounts of information, reduced the power of the test, and could not handle missing data effectively, even resulting in incorrect conclusions. GLIMMIX was the best choice for variance analysis and means comparison of repeated measure data, because it was easy to use, and had powerful function, high reliability, and ability to handle missing data. At present, there was few relevant report in China, and this method would be very practical and innovative in this field.

Anatomy characteristics and IbEXP1 gene expression of tuberization under ammonia nitrogen treatment in sweet potato

WANG Cui-Juan, CHAI Sha-Sha, SHI Chun-Yu, ZHU Hong, TAN Zhong-Peng, JI Jie, REN Guo-Bo

Acta Agronomica Sinica. 2021, 47(2):  305-319.  doi:10.3724/SP.J.1006.2021.04112

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This study chose Shangshu 19 (S19) and Jixu 23 (J23) categorized by valid tuber root number per plant as analyzing varieties and arranged treatment combinations consisted of two nitrogen forms ammonium nitrogen (A_N) and amide nitrogen (X_N) integrated with two nitrogen rates 60 kg hm^-2 (L_N60) and 180 kg hm^-2 (H_N180), using field and pot trial assays, plus a check treatment received no nitrogen supply in order to make research on the anatomical observation on sweet potato tuber root differentiation and expression characteristics of IbEXP1 gene associated with tuber root formation in ammonia nitrogen in 2014 and 2015. Our results showed that the storage root yield of Shangshu 19 associated with more valid tuber root number per plant was significantly higher than Jixu 23 at harvest stage, which was significant difference compared with each other. In addition, nitrogen levels and nitrogen forms had significant interaction effects. The 60 kg hm^-2 ammonium nitrogen treatment in two sweet potato genotypes achieved the highest final storage root yield in field experiment and showed higher valid tuber root number per plant, which attributed to the younger tubers whose root diameter between 0.5 cm and 5.0 cm during the canopy closure period. It had been observed that 60 kg hm^-2 ammonium nitrogen treatment possessed the most vessels in the primary xylem bundle and the lignified parenchyma cells of the stele tissues in the pre-cambial period, followed with possessing high level expression of IbEXP1 gene, the biggest root diameter and stele diameter and the most number of primary and secondary xylem bundles in the course of primary cambium growth. As the vascular cambium was initiated, relative expression of IbEXP1 gene at 60 kg hm^-2ammonium nitrogen treatment and the degree of parenchyma cells lignification were intermediate between no nitrogen application and high nitrogen treatments, however, the diameter of root and stele and the ratio of them were highest, which achieved the perfect harmony in lignification and division of parenchyma cells in tuberization.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of planting density and fertilization on dry matter accumulation, yield and water-fertilizer utilization of dryland potato

LIU Yan-Lan, GUO Xian-Shi, ZHANG Xu-Cheng, MA Ming-Sheng, WANG Hong-Kang

Acta Agronomica Sinica. 2021, 47(2):  320-331.  doi:10.3724/SP.J.1006.2021.04100

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It is important to increase potato production and the natural resource utilization efficiency in dryland farming system. A field experiment was conducted using Longshu 10 with three planting modes from 2017 to 2019, including farmer mode (CK), the mode with high yield and efficiency (YE), and higher yield mode (HY). The leaf area index (LAI), SPAD, photosynthetic rate, accumulation and remobilization of dry matter, water use efficiency (WUE) and fertilizer use efficiency (FUE) was investigated. The results showed that LAI and SPAD were increased in YE and HY compared to CK, and it was more significant in 2017 when there was less rainfall. Meanwhile, less reduction in LAI and SPAD after tubers enlargement resulted in an increase of canopy photosynthetic rate by 29.9%, 34.7% (in 2018 and 2019), and 40.2%, 50.5% (in 2018 and 2019) during the expanding stage and starch accumulation stage, respectively. Average aboveground dry matter in YE and HY was higher than CK by 123.1% and 118.5% in the enlargement stage due to higher LAI and photosynthetic rate. The contribution rate of assimilation after potato tuber enlargement in YE and HE was higher than CK by 22.56% and 19.29%, resulting in an average potato production increase of 47.93% and 47.78%, and average water use efficiency increased by 77.59% and 75.85%, respectively. YE and HY advantaged in tuber production and income improvement. Compared with CK, the net income increased by 7330.3 Yuan hm^-2 and 6024.6 Yuan hm^-2 in 2017 to 2019, respectively. The accumulation of N, P, and K was significantly enhanced due to large population canopy and high plant biomass accumulation. Compared to CK, N and P use efficiency, and the harvest index of N and P was increased under YE mode by 15.21%, 17.20% and 3.85%, 7.79%, respectively, and the N use efficiency was increased by 12.37% under HY mode. WUE, N, and P use efficiency of YE mode was higher than HY by 2.05%, 2.53%, and 23.41%, respectively, and the net income increased by 1305.7 Yuan hm^-2. Therefore, replacement of slow-release urea with organic manure by 40% and improvement of planting density with 60,000 plants hm^-2 in YE mode potentially increased in water use efficiency, nutrient use efficiency, high canopy photosynthetic rate maintenances, and remobilization of dry matter from stem and leaf to tubers. In conclusion, YE as a high tuber production and resource use efficiency planting mode, is recommended in semi-arid areas with black-film mulched potato cultivation regime.

Development and application of a near infrared spectroscopy model for predicting high sucrose content of peanut seed

LEI Yong, WANG Zhi-Hui, HUAI Dong-Xin, GAO Hua-Yuan, YAN Li-Ying, LI Jian-Guo, LI Wei-Tao, CHEN Yu-Ning, KANG Yan-Ping, LIU Hai-Long, WANG Xin, XUE Xiao-Meng, JIANG Hui-Fang, LIAO Bo-Shou

Acta Agronomica Sinica. 2021, 47(2):  332-341.  doi:10.3724/SP.J.1006.2021.04106

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Sugar content is an important factor affecting the flavor and processing characteristics of peanut (Arachis hypogaea L.) kernel and the sucrose content accounts for more than 90% of the total sugar content in peanut kernel. High-efficiency detection approach for sucrose content is crucial in developing high sucrose peanut varieties. In this study, 185 peanut genotypes with diversified sucrose contents were scanned in wave length of 1100-2500 nm for constructing a near-infrared spectrum of naturally dried seeds. The sucrose contents were determined by high performance liquid chromatography (HPLC) combined with standard curve method. A near-infrared calibration model of peanut seed sucrose content was established by partial least square method (PLS). For sucrose content, the coefficient of determinations (R²) was 0.962 with mean square deviation of 0.383. The coefficient of correlation between the predicted values and chemically tested value were 0.947 in 20 external samples, indicating that the model could predict sucrose content of peanut kernel. Six new sweet peanut lines with sucrose content over 7%, oleic acid over 78%, oil content less than 48% and desirable agronomic characters were selected among the hybrid progenies of “Jihua 02-1-4 × Zhonghua 26”.

Effects of long-term nitrogen fertilization with different levels on sorghum grain yield, nitrogen use characteristics and soil nitrate distribution

WANG Yuan, WANG Jin-Song, DONG Er-Wei, WU Ai-Lian, JIAO Xiao-Yan

Acta Agronomica Sinica. 2021, 47(2):  342-350.  doi:10.3724/SP.J.1006.2021.04091

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To determine a suitable nitrogen fertilizer application rate, an experiment was conducted using Jinza 34, Liaoza 27, Jinsi 2, Jinnuo 3, and Fenjiuliang 1 with six nitrogen (N) fertilization levels, including 0 (N0), 75 (N75), 150 (N150), 225 (N225), 300 (N300), and 450 kg hm^-2 (N450). The effects of long-term nitrogen fertilization with different levels on sorghum grain yield, nitrogen use characteristics and soil nitrate nitrogen distribution were investigated. The grain yield, grain number and N accumulation of sorghum increased initially and then tended to be stabile with the increase of nitrogen fertilizer application. Among them, the maximum increase of sorghum under N75 treatment compared with that under N0 treatment was 23.68%, 48.05%, and 51.86%, respectively. With the increase of nitrogen fertilizer application, the grain starch content decreased, while the grain starch yield increased firstly and then decreased. Nitrogen apparent recovery rate, nitrogen fertilizer agronomic efficiency and nitrogen use efficiency which were accumulated for five years were reduced significantly with the increase of nitrogen fertilizer application. Compared with the N150 treatment, nitrogen use efficiency accumulated for five years under N75 treatment, which was 63.01%, was increased by 76.91%. When nitrogen fertilizer application was beyond 225 kg hm^-2, after four to five years later, nitrate nitrogen residue was increased rapidly in the 60-200 cm soil layer year by year, NO₃^--N accumulation peaks distributed in the 0-200 cm soil layer and the risk of nitrate nitrogen leaching was increased. In view of the yield, starch yield, nitrogen utilization and environmental benefit, the reasonable nitrogen fertilizer application for sorghum was between 75 kg hm^-2 and 150 kg hm^-2.

Yield gaps of rice-wheat double cropping and its relationship with resource utilization in Yangtze-Huaihe Rivers region

DU Xiang-Bei, XI Min, KONG Ling-Cong, WU Wen-Ge, CHEN Jin-Hua, XU You-Zun, ZHOU Yong-Jin

Acta Agronomica Sinica. 2021, 47(2):  351-358.  doi:10.3724/SP.J.1006.2021.02028

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The Yangtze-Huaihe rivers region is an important production base of rice and wheat in China. It is necessary to clarify the differences and formation mechanism between different yield levels in the region, and to explore the limiting factors for regional grain production, which can provide scientific basis and reference for the management practices to reduce the annual yield gap in the Yangtze-Huaihe rivers region. Based on annual rice-wheat production situation, crop yield was divided into three different levels, farmer yields, experimental yields and high record yields. Yield gaps and the climate factors of different yield levels were quantified. Results showed that there were significant differences between farmer yields and experimental yields, high record yields of rice, wheat and annual in the Yangtze-Huaihe rivers region, which were 3315.9, 1537.5, and 4645.6 kg hm^-2, 7498.6, 3977.9, and 9840.9 kg hm^-2, respectively. Compared with the experimental yields, the farmer yields of rice, wheat and annual had yield increase potential of 46.2%, 29.7% and 37.3%, and 104.5%, 77.0% and 79.0% in comparison with the high record yields, respectively. The number of grains per spike was the main factor resulting in the yield difference in rice, and the grain numbers per spike and the number of spikes contributed to the yield difference in wheat. Compared with the farmer average yield, the grain numbers per spike of rice in experimental yields and high record yields were increased by 30.4% and 116.1%, respectively; the spikes and grain numbers per spike of wheat were increased by 40.9%, 70.0% and 21.8%, 19.6%, respectively. Reducing the yield gaps mainly depended on increasing the grain numbers per spike for rice, and synergistic improvement in the number of spikes and the grain numbers per spike for wheat. Cumulative radiation and low accumulated temperature during the growth period were the main climatic factors affected rice production, while excessive rainfall was the main climatic factor affected wheat production. The results suggested that in order to strengthen rice production and stabilize wheat production was an effective way to increase the annual grain production in the Yangtze-Huaihe rivers region.

Effects of different cooling methods on maize soil physical and chemical properties and yield in dryland

WANG Qi, FU Ya-Fang, SI Lei-Yong, JIN Yan, XIA Zhen-Qing, LU Hai-Dong

Acta Agronomica Sinica. 2021, 47(2):  359-367.  doi:10.3724/SP.J.1006.2021.03038

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Aiming at the phenomenon of premature senescence of plants under long-term maize plastic film mulching in rainfed and arid regions in Northwest China, adding cooling measures on mulched maize were taken to study the effects of soil temperature change on maize yield formation and analysis the changes of soil physical and chemical properties in topsoil of maize from the perspective of never changing the water conserving function of plastic film, which would provide the theoretical reference for the analysis of the early senescence in the later growth stage of ordinary plastic film maize. This experiment design using Shaandan 609 (SD 609) as tested materials, based on a 2-year field experiment, compared with the effects of three modes, ordinary plastic film mulch + black sunshade net (A), ordinary plastic film mulch + straw (B) and ordinary plastic film mulch (C) on soil temperature, soil nutrients, dry matter mass accumulation yield and water and fertilizer use efficiency in yield. The results were as follows: (1) Adding coverings on plastic film mulching (black sunshade net, straw) can effectively decrease the soil temperature and compactness, especially early stage of maize growth. (2) Compared with the control treatment C, cooling treatment A and treatment B significantly increased the content of organic matter, total nitrogen and total potassium in the later stage of maize growth, and the average partial fertilizer productivity increased by 7.24% and 6.97%, respectively. (3) Cooling treatments can delay the attenuation of green leaf area in the later stage of maize growth, improve the accumulation rate of dry matter and increase the kernel weight of maize. Compared with treatment C, the 2-year average maize yields of cooling treatment A and treatment B were increased by 6.39% and 5.93% and the average water use efficiency by 8.17% and 7.67%, respectively. In rainfed and arid regions in Northwest China, properly reducing the temperature under the film of mulched maize are helpful to improve soil physical and chemical properties, promote the accumulation of dry matter and the formation of yield and improve the high utilization efficiency of fertilizer and water.

RESEARCH NOTES

Establishment of HPLC-RID method for the determination of soluble sugars in peanut seed

LI Wei-Tao, GUO Jian-Bin, YU Bo-Lun, XU Si-Liang, CHEN Hai-Wen, WU Bei, GONG Ting-Feng, HUANG Li, LUO Huai-Yong, CHEN Yu-Ning, ZHOU Xiao-Jing, LIU Nian, CHEN Wei-Gang, JIANG Hui-Fang

Acta Agronomica Sinica. 2021, 47(2):  368-375.  doi:10.3724/SP.J.1006.2021.04110

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Edible peanut is one of the important directions of peanut breeding in China and even in the world. However, the lack of efficient detection method of soluble sugar content related to edible quality in peanut kernel limits the progress of edible peanut breeding. In this study, a method of extracting soluble sugar from peanut kernel by 80% ethanol and water bath was established. The method simplified the pre-treatment steps of samples and speeded up the extraction progress compared with the GB method. The accuracy and repeatability tests showed that this method had high repeatability accuracy and effectiveness. Then, the samples extracted by this method and GB method were both tested by HPLC-RID, it was found that the soluble sugar in mature peanut kernel was mainly sucrose, with little glucose and fructose in 20 peanut varieties. There were no significant differences between these two methods. The results of 20 peanut varieties using the method and GB method showed that the sucrose content ranged from 16.19 mg g^-1 to 83.81 mg g^-1, 15.60 mg g^-1 to 81.38 mg g^-1, and with an average of 30.41 mg g^-1, 30.20 mg g^-1. In summary, the results not only further verified the practicability of the method established in this study, but also showed that there was a huge difference in the sucrose content between these peanut varieties.

Identification of brown rust resistance and molecular detection of Bru1 gene in new and main cultivated sugarcane varieties

ZHANG Rong-Yue, WANG Xiao-Yan, YANG Kun, SHAN Hong-Li, CANG Xiao-Yan, LI Jie, WANG Chang-Mi, YIN Jiong, LUO Zhi-Ming, LI Wen-Feng, HUANG Ying-Kun

Acta Agronomica Sinica. 2021, 47(2):  376-382.  doi:10.3724/SP.J.1006.2021.04119

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The aim of this study was to assess brown rust resistance of new sugarcane varieties bred in China and main cultivated varieties in sugarcane planting area, and screen the elite new brown rust resistant varieties for popularization and application in production. In total, 60 new varieties in the national regional test of new sugarcane varieties were tested in Kaiyuan and Lincang, and 34 main cultivated varieties were studied in Lincang, Puer, and Yuxi, Yunnan province, and Yizhou, Guangxi province, China, where the incidence of brown rust was particularly high. The resistance of these sugarcane varieties to brown rust was investigated under natural inoculation and molecular marker-assisted identification was used to detect the brown rust resistance gene Bru1. The results of field survey showed that 66 (70.21%) of the 94 new and main cultivated varieties were highly resistant to moderately resistant, and 28 (29.79%) were susceptible to highly susceptible. Molecular detection indicated that Bru1 gene was found among 54 (57.45%) of the 94 new and main cultivated varieties. Some main cultivated varieties that were currently planted across large areas such as Guitang 29, Guitang 44, Dezhe 03-83, Liucheng 03-1137, Yuetang 60, and Guitang 46 were highly susceptible to brown rust, and 31 new varieties such as Yuegan 48, Funong 09-2201, Guitang 08-120, Liucheng 09-15, Zhongzhe 1, Yunzhe 08-1609, Yunrui 10-187, and Zhongtang 1201 were resistant. Therefore, in the sugarcane planting areas with high incidence of brown rust and wet and rainy climates, more effort should be eliminated the main susceptible varieties and promoted the application of new resistant varieties. This will help to achieve a reasonable distribution of varieties, fundamentally control the outbreak of disease in sugarcane planting areas, and provide security for the high-quality development of sugarcane industry in China in the future.