Table of Content

12 September 2016, Volume 42 Issue 09

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Identification of a New D1-allelic Mutant and Analysis of Its Gene Function in Rice

WANG Cui-Hong,MA Jian,WANG Shuai,TIAN Peng,QI Chang-Yan,ZHAO Zhi-Chao,WANG Jiu-Lin,WANG Jie,CHENG Zhi-Jun,ZHANG Xin,GUO Xiu-Ping,LEI Cai-Lin*

Acta Agron Sin. 2016, 42(09):  1261-1272.  doi:10.3724/SP.J.1006.2016.01261

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Plant height is one of important traits for rice yield. One genetically stable rice mutant, LTH-m3, was isolated from the cv. Lijiangxintuanheigu (LTH)-derived mutant population by mutagenesis using ethylmethane sulfonate (EMS). LTH-m3 was involved in the pathway of gibberellic acid (GA) and brassinosteroid (BR), and showed no sensitiveness to exogenous GA (GA₃) and significantly reduced sensitiveness to exogenous BR (eBL) compared with the wild type. The genetic analysis, gene cloning and transgenic complementary test confirmed that LTH-m3 was a new d1-allelic mutant with small grain and dwarf phenotypes, and a single base was mutated (G²⁵²²→A²⁵²²) in the functional dwarf gene D1 at the conjunction site of its sixth exon and intron, which caused excision of the sixth exon in mRNA and premature termination of the D1 encoded Gα protein, resulting in mutated phenotypes in the mutant. The further study showed that the D1 mutation caused obvious expression change of some dwarf genes such as SD1 and SLR1 in the mutant, and could affect the GA and BR pathways in their feedback regulations and signaling transductions in plant cells. The mutant overcome the defects of the universally blast-susceptible cv. LTH, such as too tall plant, soft stem and easy lodging, and could be utilized as an improved substitute of LTH in the future rice blast researches. The mutated D1 gene identified from the LTH-m3 mutant may be useful for further study of Gα functions and signaling pathway of GA and BR.

Global Identification and Comparison of MicroRNA in Wild and Cultivated Adzuki Bean

MA Yan-Ming,CHEN Chun-Hai,YANG Kai,LI Yi-Song,ZHAO Bo,LI Jiang,LI Yong-Qiang,WAN Ping

Acta Agron Sin. 2016, 42(09):  1273-1281.  doi:10.3724/SP.J.1006.2016.01273

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MicroRNAs (miRNAs) are a class of small regulatory RNAs with thefunction as crucial regulators that repress the expression of their target genes at the transcriptional or post-transcriptional level. Global identification of miRNA is important for the functional study. Adzuki bean (Vigna angularis) genome sequencing has beenfinished recently, but lack of a systematical analysis of miRNA. In this study, we performed deep miRNA sequencing in wild (CW108) and cultivated (JN6) adzuki beans. Our investigation not only identified the miRNAs that shared by these two species, but also found miRNAs that specifically existed in individual accession. Through comparison of the miRNA expression and their target gene predictions between the wild and cultivated adzuki beans, we found that the miRNA was diverged between them, which may be associated with plant-pathogen interaction pathway. Our study provided a valuable resource for functional analysis in adzuki bean.

Cloning and Expression Analysis of Protein Phosphatase 2A Gene TaPP2AbB″-α Promoter in Wheat

YI Heng,LI Ang,LIU Hui-Min,JING Rui-Lian

Acta Agron Sin. 2016, 42(09):  1282-1290.  doi:10.3724/SP.J.1006.2016.01282

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Protein phosphatase 2A (PP2A) is a heterotrimeric protein, consisting of a scaffolding subunit (A), a catalytic subunit (C), and a member of four families of regulatory subunits (B). PP2A plays significant roles in the pathway responding to abiotic stresses in plants. TaPP2AbB″-α, a member of regulatory subunit B″ in wheat (Triticum aestivum L.), enhanced root development and could develop more lateral roots in the gene overexpressed Arabidopsis, especially under the osmotic stresses of mannitol and NaCl. In order to elucidate transcriptional regulatory mechanism of the promoter PB″α of TaPP2AbB″-α, we isolated an 1899 bp full-length sequence of promoter PB″α from a drought-tolerant wheat cultivar Hanxuan 10. The PB″α sequence contained TATA-box, CAAT-box and a series of cis-acting elements responding to drought and osmotic stresses, such as elements of EECCRCAH1 (from ?1058 to ?1052 bp), GCCCORE (from ?1073 to ?1068 bp) and MYCCONSE (from ?1179 to ?1174 bp). The full-length promoter PB″α and five 5′-end truncated PB″α promoters in different lengths fused with the reporter gene β-glucuronidas (GUS) were transformed into Arabidopsis, respectively. The histochemical staining results showed that the full-length promoter PB″α, and the deletion fragments of PB″α-1545 and PB″α-1389 could drive GUS gene expression in shoots and roots of transgenic Arabidopsis seedlings. As the result of quantitative fluorometric GUS assay, only the expression of PB″α, PB″α-1545 and PB″α-1389 could be up-regulated by salt and osmotic stresses in transgenic Arabidopsis lines, and the active region of PB″α promoter was located in the interval between ?1389 bp and ?946 bp. In conclusion, PB″α has strong basic promoter activity which is up-regulated significantly by salt and osmotic stresses. These findings contribute to the selection of a suitable promoter for crop improvement.

Development of Functional Markers and Identification of Haplotypes for Rice Grain Shape Gene GW8

YI Chuan-Deng*, WANG De-Rong, JIANG Wei, Li Wei, CHENG Xiao-Jun, WANG Ying, ZHOU Yong, LIANG Guo-Hua, and GU Ming-Hong

Acta Agron Sin. 2016, 42(09):  1291-1297.  doi:10.3724/SP.J.1006.2016.01291

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Rice grain shape including grain length, grain width, grain thickness, and grain length-to-width ratio is a major character affecting rice yield and quality. On the basis of the alignment of gene GW8 genomic DNA sequence, three functional markers were developed on the 10-bp indel in promoter region and two missense polymorphism sites (A/C and T/G) in the exon3, respectively. Subsequently the markers were used to identify the genotypes of gene GW8 in the 294 accessions of rice mini-core collection and 65 japonica varieties certificated in Jiangsu province from 2007 to 2013. We found that the allelic variations of the three target loci had significant or very significant effects on most traits of grain shape. On the bais of the three variation sites of gene GW8, eight haplotypes (combinations) were found to have very significant effect on the four grain shape traits in the rice mini-core collection. The main haplotypes were Hap3, Hap6, and Hap1, contained in 126, 85, and 58 representative varieties, respectively; Hap7 has the most strongest effect on grain length, ratio of length to width and 1000-grain weight. While the only two haplotypes, Hap6 and Hap2, contained in 63 and 2 japonica varieties certificated in Jiangsu provice, respectively. The results paved a way to apply the useful allelic variations or haplotypes of gene GW8 in rice yield and quality breeding programs.

Molecular Cloning of Two Maize (Zea mays) CRY1a Genes and Their Expression Patterns of in Response to Different Light Treatments

YAN Lei,YANG Zong-Ju,SU Liang,XIAO Yang,GUO Lin,SONG Mei-Fang,SUN Lei,MENG Fan-Hua,BAI Jian-Rong,YANG Jian-Ping

Acta Agron Sin. 2016, 42(09):  1298-1308.  doi:10.3724/SP.J.1006.2016.01298

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Cryptochromes are blue light receptors that regulate the development of growth and circadian clock in plants. To stress study the functions of crytochrome 1 (CRY1) on photomorphogenesis and flowering regulation in maize (Zea mays L.), we isolated the cDNA clones of two ZmCRY1a genes from inbred line B73 by homologous cloning, and designated as ZmCRY1a1 and ZmCRY1a2. The length of both ZmCRY1a coding DNA sequences were 2124 nucleotides, which encoded 707 amino acid residues. Bioinformatics analyses were employed to predict their function domains and to build a phylogenetic relationship tree among plant CRY1 homologs by the DNAMAN software and the NCBI blast. The two ZmCRY1a proteins possessed three function domains: DNA photolyase, FAD binding, and Crytochrome C domains. Phylogenetic analysis indicated that the two ZmCRY1a proteins belonged to the same branch with OsCRY1a, while showing low similarity to other CRY1 proteins from dicotyledonous species, such as A. thaliana and Glycine max. The transcription abundances of two ZmCRY1a genes in different organs and in response to light treatments were detected using quantitative RT-PCR (qRT-PCR). qRT-PCR assays indicated that the two ZmCRY1a genes were highly expressed in leaf with 52.1 or 6.2 times higher than ZmCRY1a1 abundance in root, respectively. The transcription abundances of the both genes were very high under different continuous light conditions, especially in blue and far-red light. Although encoding blue light receptors, they both greatly responded to dark-to-far-red and dark-to-red transitions. In addition, their transcription abundances could also respond to photoperiod treatment (both long-day and short-day conditions). In long-day condition, ZmCRY1a1 abundance hadfive peaks and ZmCRY1a2 abundance hadfour peaks. In short-day condition, both ZmCRY1a genes had two big peaks which happened at 10 h and 14 h after transition into darkness. Our results suggest that both ZmCRY1a genes may be involved in seedling de-etiolation and flowering time control, thus their roles in crop improvement are worthy of more exploration in the future.

Mapping Quantitative Trait Loci for Seed Size and Shape Traits in Soybean

CHEN Qiang,YAN Long,DENG Ying-Ying,Xiao Er-ning,Liu Bing-Qiang,YANG Chun-Yan*,ZHANG Meng-Chen*

Acta Agron Sin. 2016, 42(09):  1309-1318.  doi:10.3724/SP.J.1006.2016.01309

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Seed size and shape not only relate to seed yield and quality, but also affect mechanical seeding in soybean (Glycine max L.). In this study, F_6:8 and F_6:9 populations derived from Jidou 12 × Heidou were used to analyze the genetic character and detect quantitative trait locus (QTL) for seed length, seed width, seed thickness, seed length-to-width ratio, seed length-to-thickness ratio, and seed width-to-thickness ratio. Softwares WinQTLCart 2.5, QTLNetwork 2.1 and IciMapping 4.1 were used to identify the additive, epistatic and environmentally interacted QTLs for seed size and shape related traits. As results, the heritability of the six traits varied from 64.01% to 79.57%. A total of 38 additive QTLs were identified to be located on 12 chromosomes, with the heritability varying from 2.21% to 10.71%.Eight of them(qSL-17-1,qSL-18-1, qSW-6-1, qST-2-1, qST-6-1, qSLT-2-2, qSWT-2-1,and qSWT-20-1)were identified using three methods, simultaneously. In the meantime, seven pairs of additive × additive epistasis were detected and the heritability of epistasis pairs ranged from 0.78 to 6.20%. Additionally, the effects of QTL by environment interaction ranged from 0.0005% to 0.3900%. The QTL identified using different mapping softwares in this study could provide a reliable theoretical basis for marker-assisted selection breeding.

Transcriptome Analysis of Stem Morphogenesis Under Shade Stress in Soybean

REN Meng-Lu,LIU Wei-Guo,LIU Ting,DU Yong-Li,DENG Yu-Chuan,ZOU Jun-Lin,YUAN Jin,YANG Wen-Yu

Acta Agron Sin. 2016, 42(09):  1319-1331.  doi:10.3724/SP.J.1006.2016.01319

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Maize-soybean relay-cropping system is a key technology in agriculture, studying the molecular mechanisms for shade stress responses of soybean grown in the intercropping system will be useful for soybean improvement by genetic manipulation. An experiment was conducted using two different shade susceptive soybean (Glycine max L.) varieties Nandou 12 and Nan032-4 to investigate the transcriptome changes in response to shade stress by RNA-seq technology. The results indicated that 287 differentially expressed genes in Nandou12 and 110 the genes in Nan032-4 were significantly affected by shade, and the expression of the genes was mainly up-regulated. Gene ontology analyses showed that differentially expressed genes were enriched in secondary cell wall biogenesis, polysaccharides synthesis, calmodulin binding, hydrolase activity and so on. In the shade treatment, differentially expressed genes responded to lignin and auxin biosynthetic processes were up-regulated in Nandou 12; and genes responded to jasmonic acid and ethylene biosynthetic processes were up-regulated, but genes responded to gibberellin metabolic process were down-regulated in Nan 032-4. However, Nandou 12 had more differentially expressed genes than Nan 032-4. The accumulateion of polysaccharides in cell wall and acceleration of secondary cell wall formation hindered the radial growth of stem making stem thinner, meanwhile the increase of hydrolysis enzyme activity accelerated the relaxation of cells, making stem longer. Nandou12 and Nan032-4 also had their particular genes to response shade, but Nandou 12 had more cell wall polysaccharides, lignin content and auxin content to increase the intensity of stem keeping a certain morphological advantage, resulting in higher lodging resistance under the shade, that is a stronger adaptability to shade.

Cloning and Characterization of Light Harvesting Chlorophyll a/b-Binding Protein Coding Gene (ScLhca3) in Sugarcane

ZHAI Yu-Shan, DENG Yu-Qing, DONG Meng, XU Qian, CHENG Guang-Yuan, PENG Lei, LIN Yan-Quan*,XU Jing-Sheng*

Acta Agron Sin. 2016, 42(09):  1332-1341.  doi:10.3724/SP.J.1006.2016.01332

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The Lhca gene family in green plants encodes several light-harvesting chlorophyll a/b-binding proteins that harvest and transfer light energy to the reaction center of photosystem I (PSI) in photosynthesis. The cDNA sequence of Lhca3 gene was firstly obtained from sugarcane leaf full-length cDNA library through sequencing and validated by homology comparison. It was designated ScLhca3 and submitted to the GenBank (accession number: KU215669). ScLhca3 contains an 804 bp open reading frame (ORF) and encodes a deduced protein of 267 amino acids, with a molecular weight and pI of 28.91 kD and 8.96, respectively. Bioinformatics analysis showed that ScLhca3 is a hydrophilic non-secretory protein with three transmembrane domains and a chlorophyll a/b binding domain. Sequence multi-alignment and phylogenetic analysis demonstrated that the ScLhca3 protein sequence shared a high identity with Lhca3 from other plants, with the specificity of species. The protokaryotic expression vector pGEX-6P-1-ScLhca3 was constructed and expressed in E. coli cells under the induction of IPTG. The subcellular localization experiment showed that the ScLhca3 fused with GFP, a reporter protein, was located on chloroplast. Real-time quantitative PCR analysis showed the expression of ScLhca3 had a clear tissue specificity, and was upregulated by CdCl₂, ABA, and H₂O₂, but downregulated by darkness, NaCl, and PEG.

Cloning, Expression, and Functional Analysis of Transcription Factor GeneGbMYB60 in Cotton

GAO Wei**,LIU Hui-Li**,TIAN Xin-Quan,ZHANG Hui,SONG Jie,YANG Yong,LONG Lu,SONG Chun-Peng*

Acta Agron Sin. 2016, 42(09):  1342-1351.  doi:10.3724/SP.J.1006.2016.01342

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MYB transcription factors are conserved proteins in all eukaryotic cell, which play important roles in plant growth, development, metabolism, abiotic and biotic stress resistance, as well as phytohormone-mediated signal transduction. In this research, a MYB gene was isolated from the sea-island cotton cultivar Hai 7124. This gene was named GbMYB60 based on the sequence similarity search and phylogenetic analysis. The full-length of GbMYB60coding sequenceis 990 bp, and GbMYB60 encodes a 36.9 kD R2R3-type MYB protein, which is specifically located in nucleus of plant cell. GbMYB60 was preferentially expressed in leaf and induced by abiotic stresses (such as salt, mannitol, cold, and heat) and phytohormones (abscisic acid, ethephon, methyl jasmonate and salicylic acid) treatments, but the general expression of GbMYB60 was low in all tissues. Salt and mannitol tolerances were analyzed in control and GbMYB60 silenced-cotton generated by virus-induced gene silencing system, and the results showed that GbMYB60 positively regulated cotton tolerance to salt but not to mannitol.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Grain Quality and Its Response to Nitrogen Fertilizer in Mid-season Indica Rice Varieties Planted in Different Decades from 1950s to 2010s

TAO Jin,QIAN Xi-Yang,JU Cheng-Xin,LIU Li-Jun,ZHANG Hao,GU Jun-Fei,WANG Zhi-Qin,YANG Jian-Chang*

Acta Agron Sin. 2016, 42(09):  1352-1362.  doi:10.3724/SP.J.1006.2016.01352

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Understanding the changes in grain quality and its response to nitrogen (N) fertilizer during the improvement of crop varieties has great significance in both crop breeding and cultivation. This study aimed to investigate the changes in grain yield and quality during the improvement of mid-season indica rice varieties and the effect of N fertilizer application on the quality. Twelve representative mid-season indica rice varieties (including hybrid combinations) grown in Jiangsu Province during the last 70 years were used with three N application treatments: 0 kg N ha^–1 (zero N, 0N), 210 kg N ha^–1 (medium amount of N, MN), and 300 kg N ha^–1 (high amount of N, HN). These varieties were divided into four groups, including 1940-1950s, 1960-1970s, 1980-1990s, and 2000-2010s (super rice), according to their application times. With the variety improvement, grain yield was significantly increased, and the head rice percentage, chalkiness, ratio of length to width, amylose content, gel consistency, protein components, and rapid viscosity analyzer (RVA) pasting properties were all significantly improved. However, chalkiness for modern varieties was still high. Grain yield was the highest in HN for super rice varieties, and in MN, for other varieties or no significant difference between MN and HN. With the increase in N application, protein content and chalkiness increased, taste quality decreased which was evidenced by the reduction in breakdown values and the increase in setback values. The contents of K, P, S, Ca, and Mg in the head rice decreased in HN compared with those in 0N or MN. The results demonstrate that the improvement of mid-season indica rice varieties markedly improves both grain yield and quality. Generally, increasing N fertilizer application especially up to the HN level could decrease rice quality. How to increase both grain yield and quality through optimizing N management is still a question to be studied.

Accumulation, Translocation and Utilization Characteristics of Nitrogen in Yongyou 12 Yielding over 13.5 t ha^-1

WEI Huan-He,MENG Tian-Yao,LI Chao,ZHANG Hong-Cheng,DAI Qi-Gen,MA Rong-Rong,WANG Xiao-Yan,YANG Yun-Wen

Acta Agron Sin. 2016, 42(09):  1363-1373.  doi:10.3724/SP.J.1006.2016.01363

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In order to determine the absorption and accumulation of nitrogen (N) in super high yielding rice population of Yongyou 12, the field experiments were conducted with these populations of high yield (HY, 10.5–12.0 t ha^-1), higher yield (HRY, 12.0–13.5 t ha^-1), and super high yield (SHY, >13.5 t ha^-1) in 2013 and 2014. Results indicated thatcompared with HRY and HY. SHY showed lower N content at jointing while higher N content at heading and maturity. SHY showed lower N accumulation at jointing while higher N accumulation at heading and maturity. N accumulation and accumulation rate from sowing to jointing of SHY was lower, while opposite trends were observed from jointing to heading and from heading to maturity for SHY. There existed a very significantly negative correlation between N accumulation from sowing to jointing and grain yield, while very significantly positive correlations were observed between N accumulation from sowing to jointing and from heading to maturity and grain yield. SHY showed higher N accumulation in leaf, stem, and panicle at heading and maturity, as well as N translocation from stem and N increase in panicle after heading. There existed a significantly positive correlation between N translocation from stem after heading and grain yield, while a very significantly positive correlation was observed between N increase in panicle after heading and grain yield. When values were averaged across two years,internal nutrient efficiency, N uptake in the panicle per hundred, partial factor productivity, and N harvest index of SHY were 50.8kg grain kg^-1, 1.97kg, 42.1kg kg^-1, and 0.552, respectively. Our study indicated that SHY showed lower N accumulation before jointing, while higher N accumulation from jointing to heading, and from heading to maturity, when compared with check. Increasing N translocation from stem after heading was beneficial to improve grain yield. N uptake in the panicle per hundred of SHY was 2.0kg, relatively low P use efficiency was observed in SHY, a great attention should be paid to improving P use efficiency.

Effect of High Temperature Stress on Bt Insecticidal Protein Content and Nitrogen Metabolism of Square in Bt Cotton

HENG Li,HU Da-Peng,WANG Gui-Xia,LYU Chun-Hua,ZHANG Xiang,CHEN Yuan,CHEN De-Hua

Acta Agron Sin. 2016, 42(09):  1374-1380.  doi:10.3724/SP.J.1006.2016.01374

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To explore the reason for low insect resistance under high temperature climate in Bt cotton production, we selected two Bt cotton cultivars as experimental material with treatments of 38°C for three, five and seven days in 2011, and 38°C/25°C at day /night for four, seven and ten days, respectively at the artificial climate chamber in 2012. The results showed that the Bt insecticidal protein contents declined within seven days under 38℃, with the largest reduction occurred within three days. Compared with control, the square Bt insecticidal protein contents decreased by 18.71% and 26.54% for cultivar Sikang3 and Sikang1, respectively. Under 38°C/25°C at day /night , the square Bt insecticidal protein contents had no obvious reduction within four days, and significant reduced after seven days with the reduction of 11.32% for SK-3and 14.18% for SK-1. Under the treatment conditions the soluble protein contents, glutamate pyruvate transaminase (GPT) activities reduced, but the free amino acid contents, protease activities increased. There existed significant negative correlation of insecticidal protein content with free amino acid contents, and protease activities ; and significantly positive correlation of insecticidal protein content with soluble protein contents, and GPT activities under high temperature stresses. Therefore, the reduced synthesis and the enhanced degradation for protein in the square under the high temperature condition resulted in the decrease of soluble protein content, including Bt insecticidal protein content. The larger reductions of the square Bt insecticidal protein content and nitrogen metabolic strength were detected in cultivar Sikang1 as confound with cultivar SK-3 under the high temperature treatments.

Relationship between Yield Loss and Flooding during Middle and Later Growth Periods in Hybrid Rice

XU Fu-Xian, ZHANG Lin, XIONG Hong, ZHOU Xing-Bing, ZHU Yong-Chuan, LIU Mao,JIANG Peng, GUO Xiao-Yi

Acta Agron Sin. 2016, 42(09):  1381-1390.  doi:10.3724/SP.J.1006.2016.01381

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Rice plants are damaged by flood water from consecutive heavy rainfalls. However, limited information is available on evaluating yield loss of rice grown under different flooding conditions. Pot experiment and field experiment were conducted to understand the yield loss of hybrid rice under different submergence depths, hours and stages in Luxian County, Sichuan Province, China, in 2012 to 2014. The results showed that yield loss was significantly influenced by flood submergence at the heading stage, followed by the booting stage and the milk-ripening stage. The yield loss was greater in the treatment of complete submergence (CS) than in that of two thirds plant height submergence (2/3PHS). Seed setting rate and grain weight of hybrid rice were significantly and negatively correlated with the submergence hours. For 2/3PHS treatment, when hybrid rice was flooded more than 100 hours at booting stage, heading stage, and milk stage, yield loss degree of hybrid rice were 50%, 60%, and 12%, respectively. For CS treatment, when hybrid rice was flooded more than 100 hours at booting stage, heading stage, and milk stage, yield loss degree of hybrid rice was 100% at booting stage and heading stage, while less than 25% at milk stage. The submergence hours correspending to yield loss degree of 40%, 60%, and 80% were calculated by a simulation equation. We established a model for studying the relationship between the degree of yield loss and submergence hours at different growth stages of hybrid rice with different submergence degrees, and the determination coefficient ranged from 0.6038 to 0.9868. When hybrid rice was submerged for 56.3 hours at booting, heading and milk-ripening stages, respectively, the error difference of yield loss degree was 3.63%?6.81% between the measured and predicted values. Our result indicated that yield loss can be accuracy estimated by this model in rice production under flooding damage.

Effect of ExogenousPolyamines on Mechanism of Floret Degeneration in Wheat

Lü Xiao-Kang,WEN Xiao-Xia,LIAO Yun-Cheng,LIU Yang*

Acta Agron Sin. 2016, 42(09):  1391-1401.  doi:10.3724/SP.J.1006.2016.01391

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Kernel number per spike has a close relationship with floret degeneration in wheat, which is regulated greatly by polyamines (PAs), one of important plant growth regulators. In this study, we applied exogenous spermine (Spm), spermidine (Spd) and putrescine (Put) to the young spikes of cultivars Shuangda 1 (large-spike type) and Xinong 538 (small-spike type) to investigate the effects of PAs on floret degeneration,endogenous hormones, and the carbon and nitrogen changes in wheat floret. The results indicated that exogenous Spd and Spm had similar effects on floret degeneration whereas exogenous Put was in function. In the treatments with external Spd and Spm applied, the floret degeneration was inhibited and the number of fertile floretsincreased significantly. In the external Put treatment, floret degeneration aggravated and the fertile floret number decreased significantly. Such influence by external PAswas different in upper and lower florets of a spike and the upper florets (inferior florets) showed greater effects than the lower ones (superior florets). The concerntrations of endogenous Spd and Spm, zeatin (Z) + zeatin ridoside (ZR),and the ratio of Z+ZR-to-abscisic acid (ABA)in inferior florets increased after applying exogenous Spd and Spm. However, the evolution rate of endogenous ethylene (ETH) in inferior floret decreased. As a result, the total soluble sugar and protein contents increased significantly in inferior floret. In contrast, exogenous Put showed reverse effects compared to Spd and Spm. Our results indicate that PAswere involved in the regulation of floret degeneration by changing the endogenous hormone concerntrations and the carbon and nitrogen metabolism in wheat plants.

RESEARCH NOTES

Effect of Heat Stress on Spikelet Degeneration and Grain Filling at Panicle Initiation Period of Rice

WANG Ya-Liang**,ZHANG Yu-Ping**,ZHU De-Feng*,XIANG Jing,WU Hui,CHEN Hui-Zhe,ZHANG Yi-Kai

Acta Agron Sin. 2016, 42(09):  1402-1410.  doi:10.3724/SP.J.1006.2016.01402

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Pot experiment was conducted to investigate the effects of heat stress on rice spikelets degeneration and grain filling at panicle initiation stage. A tolerant (Huanghuazhan) and a susceptible (Fengliangyou 6) cultivars were treated in phytotron with high temperature (10:00–15:00, 40℃) and normal temperature (10:00–15:00, 32℃) for one, three, five, seven, and nine days at last leaf emergence stage, with these grown under natural condition as control. The results indicated that the ratio of spikelet degeneration increased greatly with increasing heat-treating time. The ratio of spikelet degeneration of Huanghuazhan increased 45.8% and 62.9% after nine days under high temperature as compared with normal temperature treatment and control, and the ratio of Fengliangyou6 increased 81.7% and 136.1% in the same treatment, showing higher ratio of spikelet degeneration in Fengliangyou6 than Huanghuazhan. The pollen activity significantly decreased after one day under high temperature stress, and anther formation significantly inhibited after five days under high temperature stress. Bad anther formation and poor pollen activity under heat stress resulting in seed-setting rate significantly decreased. Spikelet length and grain filling of two cultivars decreased due to heat stress effect, resulting in a significant reduction of grain weight, with a larger reduction rate in Fengliangyou6 than in Huanghuazhan. Grain filling reduced significantly after five days of high temperature treatment. According to the study, heat stress at last leaf emergence stage may sharply decrease rice yield, and corresponding cultivation measures should be strengthened in production.

Identification of Resistance to Brown Rust and Molecular Detection of Bru1 Gene in 101 Main Sugarcane Breeding Parents in China

LI Wen-Feng,WANG Xiao-Fan,HUANG Ying-Fun*,ZHANG Rong-Yue,SHAN Hong-Li,LUO Zhi-Ming,YIN Jiong

Acta Agron Sin. 2016, 42(09):  1411-1416.  doi:10.3724/SP.J.1006.2016.01411

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Sugarcane brown rust induced by Puccinia melanocephala is an important global disease. Bru1 is a major brown rust resistance gene with a broad-spectrum resistance against various brown rust pathogens originating from different countries. In order to assess the resistance level of main sugarcane breeding parents to Puccinia melanocephala, and determine the distribution of the Bru1 gene in these breeding parents in China, 101 main sugarcane breeding parents collected from the Chinese National Nursery of Sugarcane Germplasm Resources were evaluated and identified for their brown rust resistance at the seedling stage and for the presence of the brown rust resistance gene Bru1. Bru1 was detected to present in 48 (47.5%) resistant clones out of the 101 tested parental lines, indicating that brown rust resistance in main sugarcane breeding parents in China is primarily controlled by Bru1. The absence of Bru1 in the other 29 resistant and 24 susceptible parental lines suggests that they may carry brown rust resistance-associated genes other than Bru1. These results may facilitate future efforts to breed varieties with improved resistance to brown rust and may provide resistant parental lines for selecting and planting elite resistant varieties to effectively control brown rust disease in sugarcane.