Table of Content

12 February 2019, Volume 45 Issue 2

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Identification of maize flowering gene co-expression modules by WGCNA

Yu-Xin YANG,Zhi-Qin SANG,Cheng XU,Wen-Shuang DAI,Cheng ZOU

Acta Agronomica Sinica. 2019, 45(2):  161-174.  doi:10.3724/SP.J.1006.2019.83053

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Weighted gene co-expression network analysis (WGCNA) is one of the research methods in systematic biology. It can effectively analyze the complex samples, and has been extensively used in the analysis of complicated traits for many samples. Weighted gene co-expression network has the characteristics of scale-free distribution and could construct the scale free network. The genes with similar expression level can be clustered and assigned to a module, then the relationships between co-expression modules and specific tissues can be furtherly analyzed. Our research utilized the transcriptome data of 14 different tissues of maize (Zea mays L.) inbred line B73, and calculated the gene expression level of the whole genome. Through filtering out the genes with low expression level we finally got 22,426 genes with high expression level to construct the gene expression matrix. We utilized the different tissues as the trait to construct the trait matrix. The weighted gene co-expression network analysis packages of R software was used to perform the co-expression network analysis, and 20 co-expression modules were identified. We finally obtained 14 tissue specific modules which were highly correlated with traits (r > 0.65). The enrichment analysis tool Agrigo was taken to perform the GO enrichment of the tissue specific module genes, all the 14 tissues could be enriched in GO terms. Flowering is one of the important agronomic traits in the life cycle of maize controlled by external environment signals and genetic factors. Maize flowering not only represents the transition from the vegetative growth to reproductive growth, also relates to grain yield, plant height and resistance. In our research, we detected eight tissue specific modules, which could be obtained within flowering time related pathways. In addition, 17 flowering genes which have been reported in the literatures were assigned to the co-expression modules, and mainly assigned to the Blue and Darkmagenta modules. Therefore, we focused on the network of Blue and Darkmagenta modules. Our research calculated the gene expression abundances, and detected several flowering time related modules, which will contribute to revealing the genetic mechanism of maize flowering time regulation.

Genome-wide association of roots, hypocotyls and fresh weight at germination stage under as stress in Brassica napus L.

Cun-Min QU,Guo-Qiang MA,Mei-Chen ZHU,Xiao-Hu HUANG,Le-Dong JIA,Shu-Xian WANG,Hui-Yan ZHAO,Xin-Fu XU,Kun LU,Jia-Na LI,Rui WANG

Acta Agronomica Sinica. 2019, 45(2):  175-187.  doi:10.3724/SP.J.1006.2019.84093

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Brassica napus is an optimum crop for repairing the heavy metal pollution of soil. To identify the associated SNP locus and candidate genes with arsenic (As) stress tolerance in B. napus, we measured and performed genome-wide association studies (GWAS) on relative root length (RRL), relative hypocotyl length (RHL), and relative fresh weight (RFW) of 140 rapeseed accessions by the Brassica 60K Illumina Infinium SNP array. In total, 15 SNPs significantly associated with RRL, 20 loci with RHL, and 35 SNP with RFW were identified, and each of SNP explained 13.31%-24.39%, 18.04%-33.82%, and 20.19%-25.06% of observed phenotypic variation, respectively. The most notable significant SNPs were located on chromosomes A02, A07, and C02, which were repeatedly detected and associated with RRL, RHL, and RFW simultaneously. Based on the rapeseed genome annotation of the linkage disequilibrium (LD) regions, we predicted 61 As resistance of candidate genes, among them, PHT3;3, PHT1;9, GST, OTC5, NRAMP1, and ZIP12, were related to the heavy metal absorbing and transporting. With the results of qRT-PCR, the PHT3;3 and PHT1;9 were obviously induced by As stress treatment in roots, hypocotyls and leaves, indicating that they were the important candidate genes related to As absorption and transport in B. napus. These results provide a reference for elucidating the regulation mechanism of candidate genes and improving agronomic traits in B. napus under As stress.

A new method of synthesizing Brassica napus by crossing B. oleracea with the allohexaploid derived from hybrid between B. napus and B. rapa

Fang YUE,Lei WANG,Yan-Gui CHEN,Xiao-Xia XIN,Qin-Fei LI,Jia-Qin MEI,Zhi-Yong XIONG,Wei QIAN

Acta Agronomica Sinica. 2019, 45(2):  188-195.  doi:10.3724/SP.J.1006.2019.84055

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It is an important way to improve Brassica napus (A ⁿA ⁿC ⁿC ⁿ) try using its parental species. Here a hexaploid method was proposed to synthesize B. napus by crossing B. oleracea (C ^oC ^o) with the hexaploid derived from the interspecific hybridization between B. napus and B. rapa. The hexaploid (A ^rA ^rA ⁿA ⁿC ⁿC ⁿ) was developed by crossing B. napus cv. ‘Zhongshuang 11’ with B. rapa cv. ‘SWU07’, and followed by chromosome doubling. And the hexaploid was crossed with various types of B. oleracea to develop new type B. napus. The hexaploid exhibited stable karyotype in three successive generations. There was no significant difference for seed setting rate between open-pollination and selfing-pollination in generations. The pollen fertility ranged from 94.6% to 98.8%. The average seed-setting rate was 5.47 and 7.93 seeds per pod for the open-pollination and selfing-pollination in three successive generations, respectively. The average crossability was 0.05, 0.04, and 0.05 seeds per pod in three successive crossing generations between the hexaploid and B. oleracea, respectively. There was no significant difference in pod setting rate and seed setting rate among the hybrids between the hexaploid and the diverse types of B. oleracea. A few seeds were obtained by crossing B. oleracea with hexaploid A ^rA ^rA ⁿA ⁿC ⁿC ⁿ in the field, suggesting that the method of hexaploid is useful to introgress the genomic components of parental species into B. napus.

Development and evaluation of InDel markers in cotton based on whole-genome re-sequencing data

Mi WU,Nian WANG,Chao SHEN,Cong HUANG,Tian-Wang WEN,Zhong-Xu LIN

Acta Agronomica Sinica. 2019, 45(2):  196-203.  doi:10.3724/SP.J.1006.2019.84100

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Insertion and deletion (InDel) are abundant forms of genetic variation in the genome. InDel has been recognized as an ideal source for marker development due to its high-density distribution and genotyping efficiency. In this study, the whole genome re-sequencing data of 262 upland cotton accessions were applied to identify 3206 InDel markers, and 320 markers with uniform distribution across the genome were selected to be evaluated. Eighty-seven polymorphic markers were identified, accounting for 26.88% of screened markers. A total of 160 allelic loci were detected using the 87 polymorphic markers in the 262 upland cotton accessions with an average polymorphic information content (PIC) of 0.3073 (ranging from 0.0836 to 0.3750) and an average genetic diversity of 0.3876 (ranging from 0.0874 to 0.5000), indicating a relatively low genetic diversity. Population structure analysis revealed extensive admixture and identified two subgroups, clustering analysis and principal component analysis supported the subgroups identified by STRUCTURE. Association analysis were performed by MLM (Mixed linear model), and 65 marker loci were associated with fiber quality traits (P < 0.01), explaining 2.57%-8.12% of the phenotypic variation. Genome-wide and gel based InDel markers developed based on re-sequencing data in this study provide a facile tool for cotton germplasm resources research and molecular marker assisted selection breeding.

Cloning and characterization of phytochrome interacting factor 4 (BnaPIF4) gene from Brassica napus L.

Tao FENG,Chun-Yun GUAN

Acta Agronomica Sinica. 2019, 45(2):  204-213.  doi:10.3724/SP.J.1006.2019.84085

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Phytochrome interacting factor 4 (PIF4) is a key transcription factor in light signaling pathway of plants, PIF4 interacts with Brassinazole-resistant (BZR) to mediate the interaction between light signal and brassinosteroid signal and participates in plant photoresponse. In this study, two novel PIF4 gene were isolated from Brassica napus L. cv. Xiangyou 15, they were identified on chromosomes A03 and C03 and encoding 413 and 414 amino acids, respectively, named as BnaPIF4_A03 and BnaPIF4_C03, their coding sequence (CDS), full-length mRNA and full-length gene were 1242 bp and 1245 bp, 1701 bp and 1731 bp, 2527 bp and 2665 bp, respectively. BnaPIF4_A03 and BnaPIF4_C03 had seven and eight exons, six and seven introns, respectively. Compared with the sequenced Zhongshuang 11, BnaPIF4_A03 gene had a single base insertion mutation in the first intron, a deletion mutation in the fourth and sixth introns, and a longer 3'-UTR. Other sequences of the two genes did not differ between Xiangyou 15 and Zhongshuang 11. The BnaPIF4_A03 and BnaPIF4_C03 gene-encoded proteins had a typical plant bHLH domain and were subcellularly localized in the nucleus. They are typical plant PIF4 proteins. Multiple sequence alignment and phylogenetic analysis showed that the BnaPIF4 protein was highly homologous to the PIF4 protein of Brassica oleracea, Arabidopsis thalian, and Eruca sativa. The evolutionary relationship of PIF4 protein was consistent with that of species, and the PIF4 proteins in the closely related species are highly clustered in the phylogenetic tree. PIF4 protein repeats were observed in a large number of plants and the degree of differentiation of PIF4 was lower in lower plants than in higher plants. It indicates that PIF4 protein differentiation is a late evolutionary event and there may be functional redundancy in PIF4 protein. Yeast hybridization experiments showed that there were interactions between BnaPIF4 and BnaBZR proteins, but BnaPIF4 could not interact with the promoter of BnaBZR gene, indicating that BnaPIF4 interacts with BnaBZR at the protein level but not at the transcription level. The genes expression patterns of BnaPIF4_A03 and BnaPIF4_C03 in Xiangyou 15 were consistent. BnaPIF4 gene was mainly expressed in the green tissue of B. napus L., with higher expression levels in stem epidermis, immature pods and leaves, and lower expression levels in flowers and roots, and the gene expression level of BnaPIF4 gradually decreased in the development process of B. napus L.

Genetic diversity and population structure analysis by SSR markers in waxy maize

Yuan LU,Wei-Da AI,Qing HAN,Yi-Fa WANG,Hong-Yang LI,Yu-Ji QU,Biao SHI,Xue-Fang SHEN

Acta Agronomica Sinica. 2019, 45(2):  214-224.  doi:10.3724/SP.J.1006.2019.83008

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To understand the genetic basis of waxy maize (Zea mays L. var. ceratina Kulesh), 87 waxy maize inbred lines were screened by 29 pairs of SSR markers for genetic diversity analysis. Totally, 180 alleles were detected in this population, with an average of 6 alleles per locus. Polymorphic information content (PIC) ranged from 0.308 to 0.915, with an average of 0.572. The genetic similarity between materials ranged from 0.49 to 0.93 with an average of 0.66. Based on the UPGMA (unweighted pair-group method with arithmetic means) cluster analysis, divided 87 waxy maize inbred lines into four groups with genetic similarity of 0.64, including 9, 66, 10, and 2 materials. In addition, 87 waxy maize inbred lines were also divided into four genetic subpopulations, including 24, 25, 19, and 19 materials, by the population genetic structure analysis. Further study showed that genetic variation among most of waxy maize inbred lines in this population was relatively simple. This study provides a germplasm base and theoretical basis for new variety breeding and evolutionary genetics analysis of waxy maize.

Identification of fertility restoration and molecular mapping of restorer genes in two maize restore lines of CMS-C

Bi-Tao MOU,Zhuo-Fan ZHAO,Ling YUE,Chuan LI,Jun ZHANG,Zhang-Bo LI,Han SHEN,Mo-Ju CAO

Acta Agronomica Sinica. 2019, 45(2):  225-234.  doi:10.3724/SP.J.1006.2019.083033

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The objective of the present study was to identify novel and powerful restorer lines for CMS-C. So maize inbred lines Z16 and 7250-14-1 were crossed with both isonuclear alloplasmic and isoplasmic allonuclear CMS-C, CMS-T, and CMS-S male sterile lines. Self-cross and back-cross were conducted for some of the fertility restored F₁ for genetic analysis and restorer gene mapping. Male fertility expression was investigated for all the F₁, F₂ and backcross populations, showing that Z16 and 7250-14-1 could restore the fertility for C Huangzaosi, C478, C698-3, and CMo17 completely, and partly restore the fertility for C48-2. Z16 could not restore the fertility for G48-2, EC48-2, ES48-2, RB48-2, and Lei48-2, while 7250-14-1 could partly restore the fertility for G48-2, EC48-2, and ES48-2, and maintain the sterility for RB48-2 and Lei48-2. Both Z16 and 7250-14-1 couldn’t restore the fertility of CMS-T, and partly restore the fertility for CMS-S. Genetic analysis showed that the fertility restoration was controlled by a pair of dominant genes for Z16 when crossed with C478 or C Huangzaosi. But for 7250-14-1, the fertility restoration was controlled by a pair of dominant genes for C Huangzaosi, and two pairs of complementary dominant genes for C478. Both of the restorer genes for Z16 and 7250-14-1 were mapped on the short arm of chromosome 8 by molecular markers. For Z16, it was mapped within a physical distance of 494 kb from the marker B-1 to the end of the chromosome, and for 7250-14-1, it was located between B-1 and Chr8-86080, with physical distance of 249 kb. This study not only provides some information for the practical application of Z16 and 7250-14-1, but also lays a foundation for the cloning and functional analysis of restorer genes.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Suppression mechanism of volatile sprout-inhibitors on potato tuber sprouting

Xue ZOU, Fan DING, Jin-Long YU, Jie PENG, Meng-Sheng DENG, Yu WANG, Li-Fang LIU, Kai-Zong YU-HAN, Nian-Wei CHEN, Xi-Yao WANG

Acta Agronomica Sinica. 2019, 45(2):  235-247.  doi:10.3724/SP.J.1006.2019.84063

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Tuber sprouting losses commercial value. In this experiment, the sprout inhibition abilities of naphthalene, camphor, menthol were researched and the acting mechanism by RNA-seq, iTRAQ was explained. The inhibition abilities showed a trend of menthol > camphor > naphthalene. The metabolic consumption was reduced due to sprouting inhibition and the tuber weight loss of menthol treatment was only 36% of the control loss in 180 days storage. Compared with the control, about 1227 (299) and 296 (204) genes and proteins whose expression levels were significantly up-regulated (or down-regulated) were detected respectively in sprouting tuber with camphor treatment for three days. Those genes and proteins mainly involved in response to stimulus and defense response. Transcripts of PEL, PME, PG related to pectin degradation, CYP77A6, HPFT, WES related to cutin synthesis, ACO related to synthesis of ethylene, and GATA4L coding transcription factor were upward with dormancy release during storage. Relative expression of those genes was stimulated at different degrees in camphor treatment at the early stage, but significantly inhibited at the middle and late stages, showing 0.68%-23.35% of the control expression at 49 days. Menthol treatment maintained these genes with low level expression in tuber, but significantly increased the expression of cell cycle inhibitor gene KRP4 to 15.9 times of control. Camphor treatment increased transcripts of genes WRKY75, STH-2, RBOH participating in plant-pathogen interaction pathway to the highest levels at sprouting stage. Therefore, we can conclude that camphor and menthol suppress the growth and development of sprouting tuber, eventually kill the bud and reduce the tuber weight loss during storage. Camphor treatment promotes the biosynthesis of protective substances to resist stress at the early stage and strengthen the resistance to pathogen infection at the sprouting stage; menthol treatment prevents bud sprouting by increasing KRP4 expression to inhibit cell division.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Photosynthetic characteristics of senescent leaf induced by high planting density of maize at heading stage in the field

Han-Yu WU,Ya-Jun ZHANG,Wang-Feng ZHANG,Ke-Ru WANG,Shao-Kun LI,Chuang-Dao JIANG

Acta Agronomica Sinica. 2019, 45(2):  248-255.  doi:10.3724/SP.J.1006.2019.83042

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A field experiment was conducted using maize variety “Xianyu 335” at heading stage to study the influences of planting density (15,000 plants ha ^-1, 75,000 plants ha ^-1, and 135,000 plants ha ^-1) on canopy light intensity, specific leaf weight, nitrogen content, chlorophyll content, gas exchange, and chlorophyll a fluorescence induction kinetics of the ear leaf and the fourth leaf below ear. With increasing the density, the light intensity within the canopy significantly reduced, especially around the fourth leaf below ear, and the specific leaf weight and content of nitrogen and chlorophyll in the ear leaf and the fourth leaf below ear reduced. The fluorescence induction kinetics of the ear leaf revealed little changes under different planting densities. Compared with low density, the J and I phases of the fluorescence induction kinetics curves increased slightly in the fourth leaf below ear under high density. In addition, at high planting density, the photosynthetic rate, stomatal conductance and transpiration rate of the both leaves decreased. The intercellular CO₂ concentration decreased in the ear leaf, while increased in the fourth leaf below ear. Therefore, we believe that the heterogeneity of light environment can rapidly induce senescence in the lower leaves of the canopy (such as the fourth leaf below ear) at heading stage under high planting density in the field. In the process of leaf senescence within canopy, the limiting factor of photosynthesis is not light energy capture and electron transport, while may be the decrease of carbon assimilation.

Effects of straw-incorporation combined with autumn plastic mulching on soil water consumption characteristics and winter wheat yield in arid farming areas

Yu-Zhang CHEN,Shou-Xi CHAI,Hong-Bo CHENG,Yu-Wei CHAI,Chang-Gang YANG,Kai-Min TAN,Lei CHANG

Acta Agronomica Sinica. 2019, 45(2):  256-266.  doi:10.3724/SP.J.1006.2019.71081

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Straw-incorporation and autumn plastic-film mulch are useful techniques for water-saving cultivation in semi-arid areas in northwest China. To investigate the effects of different straw-incorporation and autumn plastic-film mulching treatments on soil water consumption, winter wheat yield and water use efficiency (WUE), we conducted a two-year (2011-2012 and 2012-2013 wheat growing seasons) experiment in fixed fields in Tongwei county, Guansu province. The five treatments were corn straw-incorporation combined with autumn plastic film mulching (CF), single corn straw-incorporation (CNF), wheat straw-incorporation combined with autumn plastic film mulching (WF), single wheat straw-incorporation (WNF), and non-mulching and non-straw returning (CK). Compared with CK, CF and WF led to the increase of water storage of 0-200 cm soil layer with an average of 6.1% in 2011-2012 and 9.6% in 2012-2013, while CNF and WNF showed tender effect with the average increasing percentage of 0.7% and 4.6% in 2011-2012 and 2012-2013, respectively. In the wet year of 2011-2012, evapotranspiration of CF was 19.0 mm lower than that of CK (P < 0.05), and the evapotranspiration of CNF, WF, and WNF was similar to that of CK with no significant difference. In the dry year of 2012-2013, evapotranspiration of CK was 39.1 mm lower than the average of the other four treatments. Evapotranspiration of CF and WF significantly increased from reviving to jointing stages, but reduced from flowering to maturity stages. Deep soil water of CF and WF was consumed more than that of CK in 2012-2013. On the average of CF and WF, the grain yield and WUE were increased, compared with that of CK, by 31.0%-69.4% and 25.6%-43.0%, respectively. Particularly, CF ranked the first in improving yield (51.1% higher than CK) and WUE (41.7% higher than CK). In contrast, the average grain yield and WUE of CNF and WNF were increased by 1.2%-28.0% and 3.0%-11.6%, respectively. This study suggests that CF is an applicable technique in winter wheat cultivation in Northwest dryland.

Proteomic analysis of drought stress response on drought resistance for Vicia faba L. variety ‘Qinghai 13’ in Qinghai Plateau of China

Ping LI,Wan-Wei HOU,Yu-Jiao LIU

Acta Agronomica Sinica. 2019, 45(2):  267-275.  doi:10.3724/SP.J.1006.2019.84075

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Proteomics is playing an increasingly important role in the functional genomics era. Two-dimensional electrophoresis and mass spectrometry can be used to study the changes of proteome of crop under stress and increase the recognization and comprehension of crop response to drought stress. In order to explore the mechanism of drought resistance of Vicia faba L. variety ‘Qinghai 13’, we treated the seedlings with three days for water stress and analyzed by two-dimensional gel electrophoresis combined with mass spectrometry analysis. By t-test, 32 differentially expressed proteins spots were detected between normal and drought-stress treatments, respectively, including up- and down-regulated proteins, seven disappear protein spots and a new protein spot. Twenty-one differentially expressed proteins in seven function categories were identified and confirmed by MALDI-TOF/TOF. Among them, two participated in information transfer, one in oxygen radical scavenging, one in protective response, eight in energy metabolism, one in protein processing, five in photosynthesis, and three unknown in function. These results indicate that drought-inducible 22 kD protein, stress-inducible protein, superoxide dismutase and 17.5 kD class HSP are directly related with drought resistance, which may be the important reasons for strong drought resistance of ‘Qinghai 13’.

Leaf photosynthesis and matter production dynamic characteristics of peanut varieties with high yield and high oil content

Si-Long CHEN,Zeng-Shu CHENG,Ya-Hui SONG,Jin WANG,Yi-Jie LIU,Peng-Juan ZHANG,Yu-Rong LI

Acta Agronomica Sinica. 2019, 45(2):  276-288.  doi:10.3724/SP.J.1006.2019.84050

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The pod yield and seed oil content are important factors affecting oil yield in peanut varieties. Obviously, it is essential for high oil yield to explore the dry matter accumulate, yield, seed oil content and leaf photosynthesis characteristics. In order to clarify the formation mechanisms for high yield and high oil content in peanut varieties and to provide a theoretical base for peanut high quality and high yield cultivation techniques, a field experiment was conducted to evaluate three widely cultivated peanut varieties (Jihua 2 and Luhua 12, the high-yield and normal-oil; Jihua 4, the high-yield and high-oil). The dry matter accumulation, pod yield, seed oil content accumulation, and leaf photosynthetic characteristics were determined, showing that the pod yield and seed oil content of Jihua 4 were the highest among the three varieties used. The average rate of dry matter accumulation and the maximum rate of dry matter accumulation showed a trend of Jihua 4 > Jihua 2 > Luhua 12. The maximum weight of dry matter of Jihua 4 was moderate. The maximum seed oil accumulation rate and average seed oil accumulation rate showed a trend of Jihua 4 > Luhua 12 > Jihua 2, the active seed oil accumulation stage of Jihua 2 was the longest, while that of Jihua 4 was the shortest among the three varieties. The leaf photosynthesis potential of Jihua 4 in the entire growth period was above 20% higher than that of Jihua 2 and Luhua 12, respectively. The photosynthesis potential in pod-setting stage was very important to peanut yield, accounting for 80% over whole growing season. The leaf photosynthetic rate of Jihua 4 at pod-setting stage was more than 24% higher than that of Jihua 2 and Luhua 12. There was a significant difference in photosynthesis parameters among the three varieties. The light saturation point and CO₂ saturation point of Jihua 4 were the highest. The pod yield was positively significantly correlated with average plant dry matter accumulation rate, leaf photosynthetic rate and total leaf area duration, respectively. The seed oil content was positively significantly correlated with average plant dry matter accumulation rate, average seed oil accumulation rate, light saturation point, CO₂ saturation point. Furthermore, there existed a weak but significant correlation between pod yield and seed oil content. In conclusion, Jihua 4 has higher economic coefficient, photosynthesis potential after pod-setting stage, leaf photosynthetic rate, light saturation point and CO₂ saturation point, average accumulation rate of dry matter and seed oil, which is the main reason for higher productivity potential in yield and oil in Jihua 4.

Effects of different types of biochar on soil microorganism and rhizome diseases occurrence of flue-cured tobacco

Cheng-Jiang LI,Da-Fei LI,Gui-Su ZHOU,Long XU,Tian-Yang XU,Zheng-Xiong ZHAO

Acta Agronomica Sinica. 2019, 45(2):  289-296.  doi:10.3724/SP.J.1006.2019.01105

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A field experiment was carried out to study effects of rice husk biochar and wood biochar application respectively on rhizosphere microorganisms, rhizome diseases occurrence, and leaf yield of flue-cured tobacco. The application of biochar significantly affected the amount of rhizosphere microorganisms and the use of carbon sources of flue-cured tobacco. In turn, as well as the occurrences of granville wilt and tobacco black shank, also the yield and output value of tobacco leaf, which varied with the types of biochar. The treatment of wood biochar significantly increased the number of bacteria at vigorous growth stage and actinomycete at mature stage in flue-cured tobacco by 11.7% and 12.8% respectively, while the treatment of rice husk biochar significantly increased the number of fungus in both stages. Compared with the control, the application of biochar significantly reduced the number of Ralstonia solanacearm and Phytophthora parasitica var. nicotianac and the percentage to total microorganism. But rhizosphere microorganisms of flue-cured tobacco had the opposite effect on the carbon use ability in vigorous growing stage; before mature stage, phenolic acids and amines used by rhizosphere microorganisms were the lowest. The effect above, was more obvious in treatment of wood biochar than in treatment of rice husk biochar. Compared with control, the treatment of wood biochar decreased the incidence and disease index of granville wilt by 24.3% and 33.3%, and those of tobacco black shank decreased by 23.9% and 14.9%, while increased the output and output value by 4.7% and 21.1%. In rice husk biochar treatment, the incidence and disease index of granville wilt decreased by 18.1% and 23.9%, the incidence and disease index of tobacco black shank decreased by 15.9% and 6.0%, and the output and output value increased by 2.2% and 12.0%. In summary, the application of biochar can significantly impactive the situations of rhizosphere microorganisms of flue-cured tobacco and the utilization of different types of biochar, reducing the occurrence of granville wilt and black shank, and increasing the yield and output value of tobacco leaf. The effect of wood biochar is better.

Spatiotemporal characteristics of water requirement and agricultural drought during summer maize season in Huaihe River Basin

Chao GAO,Xue-Wen LI,Yan-Wei SUN,Ting ZHOU,Gang LUO,Cai CHEN

Acta Agronomica Sinica. 2019, 45(2):  297-309.  doi:10.3724/SP.J.1006.2019.83010

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Based on daily meteorological data from 110 stations during 1961-2015 in the Huaihe River Basin, we analyzed the spatial and temporal variations of water requirement in different growth stages of summer maize by the Penman-Monteith (P-M) formula and ‘crop coefficient method’. Crop water deficit index (CWDI) was used as an indicator of drought evaluation to reveal the spatial and temporal variation of drought in summer maize growth period. The CWDI sequence was fitted by 33 distribution functions of four categories, and an optimal probability distribution model was established to estimate the probability of drought in the growth stages of summer maize in the Huaihe River Basin. In the past 55 years, the water requirement of summer maize in whole growth period and each growth stage showed a significant decreasing trend and the spatial distribution of water requirement showed higher in central and northern region and lower in southwest and southeast region. The trend of water deficit index in summer maize growth period did not change significantly. In addition to jointing-tasseling stage, the rest of the growing stages showed water deficit in whole the basin, and the northern region was more severely affected by water deficit than the southern region. During the growth period of summer maize, the probability of drought in the sowing-emergence stage and the tasseling-milking stage was the highest. Except for the probability between 30% and 50% of severe drought in the sowing-emergence period, the drought probability of different grades in each growth stage was less than 20%.

RESEARCH NOTES

Silking duration characteristics in different maize hybrids and its response to sowing date

Yue-E LIU,Tian-Fang LYU,Jiu-Ran ZHAO,Rong-Huan WANG,Tian-Jun XU,Chuan-Yong CHEN,Yi-Tian ZHANG,Yuan-Dong WANG,Xiu-Zhi LIU

Acta Agronomica Sinica. 2019, 45(2):  310-315.  doi:10.3724/SP.J.1006.2019.83034

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Silking is an important growth stage and has important effects on maize (Zea mays L.) yield. The research of silking characteristics plays a fundamental role in maize productivity. To examine the silking characteristics difference of different maize hybrids and its responses to sowing date, we conducted an experiment with three sowing date (4/10, 5/10, 6/10) treatments using the most widely cultivated maize hybrids of Zhengdan 958 (ZD958), Xianyu 335 (XY335), and Jingke 968 (JK968). The silking duration difference between different hybrids and the relationship of silking duration with ear length variation and yield components were analyzed. The significant differences were found in silking durations with an order of XY335 (9.12 d) > ZD958 (8.94 d) > JK968 (7.68 d). The silking ratio per day was well correlated with days to silking (P < 0.05), A non-linear positive relationship existed between silking ratio per day (y) and days to silking (x). The highest silking ratio per day showed an order of XY335 (16.51%) < ZD958 (17.07%) < JK968 (19.98%). Significant differences of silking duration were found between different sowing date treatments. The silking durations of ZD958, XY335, and JK968 in different sowing date treatment ranged from 8.10 d to 9.55 d (CV = 6.57%), from 7.54 d to 10.53 d (CV = 9.40%), from 6.55 d to 8.66 d (CV = 11.68%), respectively. Silking duration significantly and positively correlated the coefficient of variation of ear length, and negatively correlated with yield and kernel number per ear. No significant correlation was found between silking duration and 1000-kernel weight. Sowing date has significant effects on silking duration. With increasing silking duration , the coefficient of variation of ear length is increased significantly, the uniformity of ear length and kernel number per ear are decreased, resulting in maize yield decrease significantly.

Development of molecular markers polymorphic between Dongxiang wild rice and Geng rice cultivar ‘Nipponbare’

Xiao-Ding MA,Jiang-Hong TANG,Jia-Ni ZHANG,Di CUI,Hui LI,Mao-Mao LI,Long-Zhi HAN

Acta Agronomica Sinica. 2019, 45(2):  316-321.  doi:10.3724/SP.J.1006.2019.82037

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Dongxiang wild rice is a type of common wild rice (Oryza rufipogon) that has the northernmost natural distribution of any wild rice species. The genome of Dongxiang wild rice differs from that of modern cultivated rice varieties (Oryza sativa). At present, a set of molecular markers that covers the entire genome of Dongxiang wild rice is lacking. In this study, we used Dongxiang wild rice and the Geng rice variety “Nipponbare” as research materials. By screening the existing collection of 1017 SSR and InDel markers and the 217 InDel markers which were designed using Dongxiang wild rice genome resequencing information, we obtained a set of 203 markers polymorphic between Dongxiang wild rice and ‘Nipponbare’, which were relatively uniformly distributed on the 12 rice chromosomes, and basically covered the entire genome, with an average inter-locus distance of 1.9 Mb. Through the genotyping of five Xian and five Geng varieties, we concluded that those 203 polymorphic molecular markers have a high application value in genotype analysis of Dongxiang wild rice and Geng rice offspring population. These results provide a powerful tool for exploring beneficial genes from Dongxiang wild rice as well as marker-assisted breeding and selection.