Table of Content

12 January 2017, Volume 43 Issue 01

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Mapping of Common Bacterial Blight Resistance Gene in Common Bean

ZHU Ji-Feng,WU Jing,WANG Lan-Fen,ZHU Zhen-Dong,WANG Shu-Min

Acta Agron Sin. 2017, 43(01):  1-8.  doi:10.3724/SP.J.1006.2017.00001

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Common bacterial blight disease is a serious disease affecting the production of common bean (Phaseolus vulgaris L.) worldwide. The common bean germplasm Longyundou 5 is the main cultivar carrying common bacterial blight resistance genein Heilongjiang province. To study the genetic mechanisms behind this resistance, we constructed 785 F₂ plants from Longyundou 5. Linkage analysis was performed on this population by using SSR markers. A linkage map covering 1648.42 cM with an average marker distance of 8.00 cM among 206 SSR markers was constructed. This map contained 12 linkage groups with a mean group length of 137.37 cM and the number of loci ranging from three to thirty-five. Combined with the results of phenotypic evaluation, QTL analysis was performed by the inclusive composite interval mapping method with QTL IciMapping v4.0. A QTL was detected between p6s249 and p6s183 on chromosome Pv06, with an additive effect of 0.44, which means the favourable gene of this locus is from Longyundou 5. The LOD score of the QTL was 5.93 and the total phenotypic variation at 14 days after inoculation was 4.61%. These results showed the effect of the QTL was low, which will play an important role in breeding durable resistant varieties of common bean. Association analysis between 11 SSR primers linked with common bacterial blight resistance and the disease rating showed that SSR marker p6s249 is excellently associated (P<0.001) with common bacterial blight resistance and can be used for marker assisted selection.

Influence of Stem Solidness on Stem Strength and Stem Solidness Associated QTLs in Bread Wheat

PAN Ting,HU Wen-Jing,LI Dong-Sheng,CHENG Xiao-Ming,WU Rong-Lin,CHENG Shun-He

Acta Agron Sin. 2017, 43(01):  9-18.  doi:10.3724/SP.J.1006.2017.00009

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Improving stem strength is an important way to increase lodging resistance of wheat. Solid stem traits, including thickness-diameter ratio of culm, stem diameter, culm wall thickness and pith diameter, are the main targets for improvement of stem strength in wheat. In the present study, an F₂ population and F_2:3 families derived from the cross N18×WYSG wereused to study the influence of stem solidness on stem strength and to identify QTLs for solidnessrelated traits. The thickness-diameter ratio of culm, stem diameter, culm wall thickness and pith diameter were significantly correlated with stem strength. By using composite interval mapping (CIM), a total of 23 QTLs for the five traitswere detected on chromosomes 1B, 3B, 4A, 4B and 5A. Phenotypic variations explained by individual QTL ranged from 3.5% to 44.0%. Pleiotropic QTLs were found on chromosomes 3B (gwm547–gwm247),4A (wmc718–wmc468) and 5A (gwm156–gwm443), all contributing very high phenotypic variations. The reliability of the marker gwm247was confirmed using 24 F₇ lines derived from the N13 (hollow stem) × WYSG (solid stem) cross. The markers linked to major QTLs could be valuable in wheat breeding for lodging resistance with marker assisted selection technology.

Construction of High-density Genetic Map and QTL Mapping for Seed Germination Traits in Sunflower under Two Water Conditions

LYU Pin,YU Hai-Feng,YU Zhi-Xian,ZHANG Yong-Hu,ZHANG Yan-Fang,WANG Ting-Ting,HOU Jian-Hua

Acta Agron Sin. 2017, 43(01):  19-30.  doi:10.3724/SP.J.1006.2017.00019

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Seed germination and emergence of sunflower are seriously affected by water stress. In this study, SSR, SRAP, and AFLP markers were applied to construct a genetic linkage map by using the F6 population derived from a cross of K55 (drought sensitive) ´ K58 (drought resistant). For mapping quantitative trait loci (QTLs) for nine traits of seed germination in sunflower,the parents and 187 F6 family lines were used to investigate seed germination traits under normal condition (CK) and 18% polyethylene glycol (PEG-6000) (drought stress). A genetic map consisting of 17 linkage groups was constructed with 1105 loci (368 SSR, 369 SRAP, 333 AFLP) which covers 3846.0 cM and the length of each linkage group varies from 147.6 to 295.5 cM, the number of markers in each linkage group varies from 10 to 165 with an average distance of 3.481 cM. As a result, a total of 33 QTLs were detected. We identified fourteen additive QTLs for germination index (GI), germination rate (GR), embryo length (EL), radicle length (RL), embryo fresh weight (EFW), radicle fresh weight (RFW) under18% PEG condition with explained phenotypic variance ranging from 6.1% to 14.0%. Nineteen additive QTLs were identified for germination energy(GE), radicle length (RL), embryo fresh weight (EFW), radicle fresh weight (RFW), embryo dry weight (EDW), radicle dry weight (RDW) under normal condition with explained phenotypic variance ranging from 6.1% to 25.8%. Each ofQefw5-2, Qefw5-1, Qefw5-4, Qrfw10, Qrfw5, and Qrl9could explain phenotypic variance over 10%. Nine QTLs affecting trait differences between stress treatment and control were identified, which are considered to directly contribute to drought tolerance. These QTLs identified could provide important reference to molecular breeding for drought-resistance during seed germination in sunflower.

Cloning and Expression Analysis of Key Gene ScD27 in Strigolactones Biosynthesis Pathway

WU Zhuan-Di**,LIU Xin-Long**,LIU Jia-Yong,ZAN Feng-Gang,LI Xu-Juan,LIU Hong-Bo,LIN Xiu-Qin, CHEN Xue-Kuan, SU Huo-Sheng,ZHAO Pei-fang,WU Cai-Wen*

Acta Agron Sin. 2017, 43(01):  31-41.  doi:10.3724/SP.J.1006.2017.00031

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Strigolactones (SLs) is a novel class of plant hormones. D27 regulating reversible metabolic process is located in up-stream of strigolactones biosynthesis pathway. In this study, primers were designed based on the conserved domains from four species inluding Oryza sativa, Zea mays, Sorghum bicolor, and Brachypodium distachyon. Using cDNA from sugarcane cultivar ROC22 as the template, the full-length cDNA sequence of D27 gene from sugarcane was cloned by RT-PCR and RACE method. This gene isnamed as ScD27, with the GenBank accession number of KP987221.1. Its length is 1379bp, and it contains an 867bp open reading frame (ORF), encoding 288 amino acid residues. ScD27 is not a secretory protein and has a molecular weight of 71.58kD, with a theoretical isoelectric point of 5.04. ScD27 is mainly located in chloroplast and the conserved domains of this protein involve two zinc finger protein structures (ZnF_TAZ and ZnF_A20). Amino acid sequences encoded by ScD27 shared more than 70% similarity with the reported amino acid sequences encoded by D27 of Sorghum bicolor, Setaria italica Beauv., Hordeum vulgare subsp. vulgareand Brachypodium distachyon. ScD27 gene was differentially expressed in different parts of sugarcane plant, with higher level of transcript in stem tip and axillary bud but much lower level in leaf, stem and root. Furthermore, the expression of ScD27 could be induced by the stresses of PEG, salt and the deficiencies of phosphorus and nutrition. These results demonstrated that ScD27 might be a key gene participating in the response to abiotic stresses during sugarcane SLs biosynthesis pathway.

Cloning and Expression Analysis of CDK Gene in Sugarcane

SU Ya-Chun**,HUANG Long**,LING Hui,WANG Zhu-Qing,LIU Feng,SU Wei-Hua,HUANG Ning,WU Qi-Bin, GAO Shi-Wu,QUE You-Xiong*

Acta Agron Sin. 2017, 43(01):  42-50.  doi:10.3724/SP.J.1006.2017.00042

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Plant cyclin-dependent kinases (CDKs) are a specific class of serine/threonine protein kinases, having synergy with cyclins, as an important acting factor in the process of cell regulation. In this study, a unigene from previous transcriptome data of sugarcane in response to sorghum mosaic virus (SrMV) infection, which exhibited highly homologous to Sorghum biocolor CDK sequence (GenBank Acc No. XP_002466536.1), was validated by RT-PCR and named as ScCDK (GenBank Acc No. KR258796) with a full-length cDNA of 1799 bp. ScCDK contained a complete open reading frame (65–1603 bp) encoding 512 amino acids, and a typical conservative CDK domain, such as ATP binding site, polypeptide substrate binding site and activation loop. Furthermore, based on the bioinformatics prediction, this soluble protein, which was most probably involved in intermediary metabolism, was located in cell nucleus and had no signal peptide but had more random coil upon secondary structure. Real-time quantitative PCR (RT-qPCR) analysis revealed that the expression of this target gene was tissue-specific, with the highest transcript level in bud, followed by the expression in stem pith, root, leaf sheath and epidermis. Besides, its expression could be up-regulated by the treatments of PEG, NaCl and ABA, with nearly 1.9-fold up-regulation of ScCDK transcript under the stress of ABA, compared with the control. These results suggest that the ScCDK may relate to the response of sugarcane to drought and osmotic stresses, meanwhile, be induced by hormones and involved in cell cycle division.

Gene Mapping and Cloning of a Premature Leaf Senescence Mutant psls1 in Rice

HUANG Ya-Min,ZHU Shan-Shan,ZHAO Zhi-Chao,PU Zhi-Gang,LIU Tian-Zhen, LUO-Sheng,ZHANGXin

Acta Agron Sin. 2017, 43(01):  51-62.  doi:10.3724/SP.J.1006.2017.00051

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Leaf early senescence directly reduces its photosynthetic capacity, decreasing crop yield and grain quality. It is of great importance to identify novel mutants and characterize their molecular and physiological mechanisms. In this paper, we reported gene mapping and cloning of a psls1 mutant (premature senescence leaf with spots) in rice. The mutant showed early senescence symptoms, including decreased chlorophyll content, over-accumulated H₂O₂, yellow-withered leaf and increased dead cell from bottom to top of plant after the 7-leaf stage. Moreover, the plant height, tiller number, panicle length, and the number of grains per panicle were significantly lower in psls1. We observedthe degradation of chloroplast, unclean thylakoid and numerous osmiophilic granules in psls1 leavesby transmission electron microscope (TEM). Genetic analysis demonstrated that the phenotype of psls1 was determined by a single recessive gene. Using genetic population derived from psls1 × IRAT129, the psls1 locus was mapped in a 89 kb region flanked by markers zs-3 and zs-8 on chromosome 7, containing 12 putative open reading frames (ORFs). Sequence analysis revealed a single-base substitution occurred in the genomic sequence of LOC_Os07g46460, which led to a 59 bp deletion in its cDNA, and therefore, predicted LOC_Os07g46460 (PSLS1), encoding a ferredoxin-dependent glutamate synthase as the candidate gene. The mRNA expression level of mutated PSLS1 decreased sharply, resulting in reduction of glutamate synthase activity and abnormal amino acid metabolism in psls1. Under low nitrogen treatment, the senescence phenotype of psls1 could occur as early as at the 3-leaf stage. These results indicated that psls1 senescence phenotype might be associated with the loss of glutamate synthase activity and the abnormal amino acid metabolism.

Fine Mapping andGenetic Effect Analysis of qKRN5.04, a Major QTL Associated with Kernel Row Number

BAI Na,LI Yong-Xiang*,JIAO Fu-Chao,CHEN Lin,LI Chun-Hui,ZHANG Deng-Feng,SONG Yan-Chun,WANG Tian-Yu,LI Yu,SHI Yun-Su*

Acta Agron Sin. 2017, 43(01):  63-71.  doi:10.3724/SP.J.1006.2017.00063

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For kernel row number (KRN), one of the important factors of maize yield, the genetic basis dissection and fine mapping of crucial gene would be greatly beneficial to maize molecular breeding. In present study, series of advanced backcross population and secondary segregation population were developed from a backcross of the derived line of four-row waxy corn (four kernel rows, as the donor parent) and Nong531 (18-22 kernel rows, as the recurrent parent). The QTL mapping for KRN was conducted by the inclusive complete interval mapping (ICIM) method in multiple environments. And a major KRN QTL, qKRN5.04, was mapped to the interval of 136.3-140.0 Mb on chromosome 5, with the largest phenotypic variation of 21.76% and the effect value of 0.80-1.76 row. Furthermore, according to recombinant analysis of secondary population, qKRN5.04 was fine mapped to the region of about 300 kb, which provided both practical InDel markers for marker-assisted selection and sufficient supports for the map-based cloning and candidate gene mining of the target locus.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effect of Biochar on Root Morphogenesis and Anatomical Structure of Rice Cultivated in Cold Region of Northeast China

ZHOU Jin-Song,YAN Ping,ZHANG Wei-Ming,ZHENG Fu-Yu,CHENG Xiao-Yi,CHEN Wen-Fu

Acta Agron Sin. 2017, 43(01):  72-81.  doi:10.3724/SP.J.1006.2017.00072

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To explore potential and practical application value of biochar in rice production in the cold region of Northeast China, we added 0-20.0% (w/w) biochar in rice nursery substrate of paddy soil and studied the root morphogenesis and anatomical structure of rice at 30 days after seed germination, The treatment of 5.0% biochar significantly increased the root length, root surface area and root volume, with the maximum value for all the root morphological indexes in the treatment of 10.0% biochar. When the biochar added more than 10.0%, the root morphological indexes started to decrease. It was indicated that the increase of root length, root surface area and root volume was the consequence of producing more fine roots. Meanwhile, when 5.0% biochar added in the rice nursery substrate, root epidermis thickness, cortex thickness, sclerenchyma tissue, number of vessels, sectional area of vessels, cortex cavity area, sectional area of whole root and root radius increased in comparison with those of control. In the treatment of 5.0%-10.0% biochar addition, all the indexes of anatomical structure of root reached the maximum. When the biochar added more than 10.0%, all the indexes of anatomical structure of root had a descending trend. It was revealed that the well-developed root epidermis and cortex were the main reason of promoting enlargement of roots when a moderate amount of biochar was added in the rice nursery substrate. Taken together, we conclude that the proper addition of 5.0%-10.0% (w/w) biochar is advantageous to the elongation, enlargement and formation of well-developed root system ,resulting in improved quality of rice seedlings in the dry rice-nursery of protected area when the paddy soil is used as the nursery substrate in the cold region of Northeast China.

Analysis of Yield Components with High Harvest Index in Brassica napusunder Environments Fitting Different Yield Levels

LU Kun,Shen Ge-Zi,LIANG Ying,FU Ming-Lian,HE Bin,TIE Lin-Mei,ZHANG Ye, PENG Liu,LI Jia-Na

Acta Agron Sin. 2017, 43(01):  82-96.  doi:10.3724/SP.J.1006.2017.00082

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Low harvest index is a bottleneck for further improvement of seed yield and oil production in rapeseed (Brassica napus). A total of 321 B. napus accessions with normal growth and maturation at both the super high yield production area Lincang, Yunnan province and the major production area of the upper Yangtze River basin, Beibei, Chongqing were chosen in this study. Variance of yield-related traits and their differences between two locations were compared, and the relationship between yield harvest index (YHI), oil production harvest index (OHI) and 17 yield component traits were also investigated by correlation and path analyses. At Yunnan, the main reasons for high yield of B. napuswereadequate illumination, big diurnal temperature difference, sufficient photosynthate, more biomass, higher number of siliques per plant and seed number per silique, especially the number of siliques on the secondary branches, which might play key roles in improvement ofB. napus yield. The silique number on the main inflorescence, primary and secondary branches was significantly and positively correlated with YHI at Chongqing, but the reverse relationship was observed between YHI and silique number on main inflorescence at Yunnan. The number of seeds per silique on the main inflorescence, primary and secondary branches at Yunnan were significantly higher than those at Chongqing, and the number of seeds per silique on the main inflorescence and primary branch showed significant or extremely significant positive correlation with YHI and OHI simultaneously at both two cultivated areas, suggesting that sufficient accumulation ofphotosynthate and high grain filling efficiency are necessary for large number of seeds per silique.Thousand-seed weights on the main inflorescence, primary and secondary branches at Yunnan were all lower than those at Chongqing, suggesting that once the photosynthate is insufficient, the seed number per plant will decrease and partial seeds will become the priority for seed-filling in B. napus, to ensure the quality of offspring seeds. Under the high yield production condition of Yunnan, thousand-seed weights on three different parts showed significant or remarkably significant positive correlation with YHI and OHI, while those at Chongqing were not, indicating that thousand-seed weight is determined by the transport capacity of photosynthate under the condition of sufficient illumination. In summary, the number of siliques on the main inflorescence andseed yield per plant are two key factors for increasing YHI under adequate illumination environment.Butthe composition of YHI is more complicated under weak illumination environment. Thus, higher YHI could be achieved when the yield components on the main inflorescence and primary branch areorganic ally integrated and biological yield is restrained.

Characteristics of Nitrogen Uptake, Utilization and Distribution in Ordered Transplanting and Optimized Broadcasting Rice

GUO Bao-Wei,ZHANG Hong-Cheng*,ZHU Da-Wei,Xu Ke,HUO Zhong-Yang,WEI Hai-Yan,DAI Qi-Gen, HU Ya-Jie,CUI Pei-Yuan

Acta Agron Sin. 2017, 43(01):  97-111.  doi:10.3724/SP.J.1006.2017.00097

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The stable super high yield of broadcasting rice relies on the ordered plantation of rice. In this study, three planting methods including ordered transplanting (OT), optimized broadcasting (OB) and cast transplanting (CT) using dry-raised rice seedlings in plastic plates with 2-hole, 3-hole, and 1-hole were used with mechanical transplanting (MT) using blanket rice seedlings as control to investigate the nitrogen uptake, utilization and translocation characteristics. Ordered transplanting and optimized broadcasting rice had lower N content at the whole growing stage, lower N accumulation at critical stage for effective tillering (CS) and elongation stage (ES), and higher N accumulation after ES significantly or very significantly than CT rice, showing N accumulation in treatments was OT>OB>CT. And 2-hole and 3-hole plants kept higher N content than 1-hole plants at each stage with proper N accumulation before ES and stronger N uptake ability after ES. N accumulation and N uptake rate in treatments after heading were 2-hole>3-hole>1-hole. Nitrogen agronomic efficiency, physiological efficiency, partial factor productivity, N requirement for 100 kg, nitrogen use efficiency for biomass production, nitrogen use efficiency for grain production, nitrogen harvest index and grain yield among different transplanting ways showed the trend of OT>OB>CT and MT. N use efficiency, partial factor productivity and nitrogen harvest index (NHI) among different hole treatments had the trend of 2-hoel>3-hole and 1-hole, and N requirement for 100 kg grain 2-hoel and 3-hole > 1-hole, while nitrogen use efficiency for biomass production and nitrogen use efficiency for grain production showed the trend of 2-hoel and 3-hole< 1-hole. N content and accumulation in panicle among different transplanting ways after heading showed the trend of OT>OB>CT, while the opposite trend was shown in culm, sheath and leaf. And N content in leaf and panicle among different hole treatments was shown 2-hoel>3-hole and 1-hole and N accumulation among different hole treatments in each organ was 2-hoel >3-hole >1-hole. N transportation and transportation rate were OT>OB>CT among different transplanting ways, and 2-hoel, 3-hole<1-hole among hole treatments. Base on the above results, we conclude that ordered transplanting and optimized broadcasting rice, especially that with 2-hoel treatment, had the rational N content and accumulation at early stage, stronger N uptake ability and higher N accumulation, transportation with higher transportation ratio after heading, and high nitrogen agronomic efficiency, physiological efficiency, partial factor productivity, N requirement for 100 kg, nitrogen use efficiency for biomass production, nitrogen use efficiency for grain production and nitrogen harvest index, which is the nutritional basis for high yield of OT and OB rice.

Identification of Alkali Tolerance of Mungbean Germplasm Resources during Germination

XU Ning,CHEN Bing-Xu,WANG Ming-Hai,BAO Shu-Ying,WANG Gui-Fang,GUO Zhong-Xiao

Acta Agron Sin. 2017, 43(01):  112-121.  doi:10.3724/SP.J.1006.2017.00112

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Mixed alkali (NaHCO₃ : Na₂CO₃ with the mole ratio of 9 : 1) was used to simulate the typical alkali stress environment in Northeast China. The seeds of 34 accessions of mungbean germplasm resources were treated with 50 mmol L^–1 solution with distilled water as control and germinated in petri dishes for seven days. The germinating energy was measured on the third day and the germination rate, hypocotyl length, radicle length, hypocotyl dry weight, and radicle dry weight were measured on the seventh day. Through the subordinative function analysis, clustering analysis, and factor analysis, the alkali tolerance of 34 mungbean materials were evaluated. All of the materials based on subordinative function were clustered into four groups: nine accessions were tolerant to alkali, e.g. Bailyu 11, 19 accessions had midium tolerance, e.g. Gonglyu 1, five accessions were sensitive to alkali, e.g. Jilyu 3, and Weilyu 7 was strongly sensitive to alkali. The vigor index, hypocotyl dry weight, and radicle length were the most significant indexes which are recommended as the suitable indexes for identifying alkali tolerance of mungbean at germination. The results lay a foundation for alkali tolerance gene mining and variety improvement in mungbean.

Effects of Plastic-Film Mulching and Supplementary Irrigation on Yield Formation and Water Use Efficiency of Hybrid Millet

GAO Liang,ZHANG Wei-Hong,DU Xiong,GUO Jiang,SONG Jin-Hui,WANG Xiao-Ming,ZHAO Zhi-Hai

Acta Agron Sin. 2017, 43(01):  122-132.  doi:10.3724/SP.J.1006.2017.00122

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Hybrid millet is a new type of foxtail millet and widely planted in semi-arid plateau area in North China. However, drought is one of the major limited factors for increasing grain yield effectively. So we conducted field experiments in 2013 (wet year) and 2014 (dry year) to examine the effect of supplementary irrigation with plastic-film mulching on yield formation and water use efficiency of hybrid millet. For hybrid millet, 40–80 days after sowing was the critical period of water requirement, the supplementary irrigation at jointing stage helped to increase seed heads quantity, from jointing to heading not less than 110 mm of evapotranspiration (ET) was the sufficient condition for producing enough biomass. Achieving a higher grain yield needed a ET of 400 mm during whole growing season. The biomass at heading stage determined the subsequent grain yield with a characteristic of “stage hierarchy determination”, supplementary irrigation with plastic-film mulching increased biomass at heading stage significantly. Under mulching of wet year or in dry year, supplementary irrigation increased dry matter production after flowering. In dry year under rainfed condition dry matter after flowering accumulated in vegetative organs, supplementary irrigation promoted to translocate the dry matter from vegetative organs into grains. Under supplementary irrigation, plastic-film mulching increased grain yield by 10.1%–18.6% and WUE by 10.7%–19.4% compared with un-mulching, respectively. In dry year, because of the persistent drought before heading, under rainfed condition plastic-film mulching resulted in a grain yield lower than un-mulching, supplementary irrigation was a necessary condition for increasing yield and WUE. In wet year, supplementary irrigation decreased WUE, plastic-film mulching increased grain yield and improved the yield-increasing effect of supplementary irrigation. In dry year, the yield-increasing effect due to supplementary irrigation was better than that due to plastic-film mulching. In conclusion, plastic-film mulching combined with suit irrigation at jointing and/or heading is an effective way to increase yield and WUE of hybrid millet.

RESEARCH NOTES

Development and Characterization of Amphidiploid Derived from Interspecific Cross between Cultivated Peanut and Its Wild Relative Arachis oteroi

LI Li-Na,,DU Pei,FU Liu-Yang,LIU Hua,XU Jing,QIN Li,YAN Mei,HAN Suo-Yi,HUANG Bing-Yan,DONG Wen-Zhao,TANG Feng-Shou,ZHANG Xin-You

Acta Agron Sin. 2017, 43(01):  133-140.  doi:10.3724/SP.J.1006.2017.00133

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Wild Arachis species are important genetic resources. To introgress resistant genes of Arachis species, developed a new amphidiploid AmE-4 through man-made cross between cultivated peanut variety Yuhua 9331 and a diploid Arachis species A. oteroi, with the assistance of following embryo rescue and chromosome doubling by colchicine treatment. AmE-4 was identified and characterized by fluorescence in situ hybridization (FISH) and SSR molecular marker. Morphological observation revealed significant differences in leaves between amphidiploid AmE-4 and Yuhua 9331, while the agronomic traits such as main stem height, length of first lateral branch and number of branches showed less difference between them. The date of first flower appearance in AmE-4 delayed sixty days compared with that in Yuhua 9331, and its pods setting and development were also poor, which would hinder its further utilization. In addition, 57 dominant or co-dominant SSR molecular markers were developed and could be used to identify translocation or introgression lines with A. oteroi chromosome fragment in future studies.

Regulation on Contents of Endogenous Hormones and Asr1 Gene Expression of Maize Seedling by Exogenous ABA under Low-temperature Stress

LI Xin-Yuan,YANG Ye,ZHANG Li-Fang,ZUO Shi-Yu,LI Li-Jie,JIAO Jian,LI Jing

Acta Agron Sin. 2017, 43(01):  141-148.  doi: 10.3724/SP.J.1006.2017.00141

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Abscisic acid (ABA) is an important signal factor under low-temperature stress. This study aimed to investigate the effect of exogenous ABA on growth regulation of maize seedlings under low-temperature stress. Maize variety “Jiulong 5” resistant to low temperature was weed with foliage spray of ABA (5, 15, 25, 35 mg L^-1) at three-leaf period under varying degrees of low-temperature, to analyze relative electric conductivity, activities of autioxidant enzymes and contents variation of endogenous ABA and IAA of maize blades, as well as Asr1 gene expression level by Real-time PCR. The relative electric conductivity of maize blades showed an increasing tendency, meanwhile, activities of SOD and POD were enhanced by exogenous ABA treatments among which SOD activity was significantly higher in ABA treatments of 15 mg L^-1 and 25 mg L^-1 than in the control under low-temperature stress. Also the synthesis of endogenous ABA and IAA were increased significantly. The expression level of Asr1 gene significantly promoted in ABA treatments of 5, 15, and 25 mg L^-1. ABA contant had a highly significant correlation with the relative expression of Asr1 gene and SOD activity and a significant correlation with POD activity. In conclusion the expression of Asr1 gene is mediated and regulated by ABA, the promotion of Asr1 gene expression also promotes the synthesis of endogenous ABA, and enhances antioxidant enzyme activities, resulting in improved maize resistance to low temperature. But the mediation and regulation of exogenous ABA have a concentration effect, showing promotion at low concentation and inhibition at high concentation.

Photosynthetic Characteristics and ¹⁴C-Assimilate Translocation in Wheat Spike during Mid- to Late-filling Stage under Water Deficit

MI Hui-Cong,XIE Shuang-Ze,LI Yue,DING Han,LYU Jin-Yin

Acta Agron Sin. 2017, 43(01):  149-154.  doi:10.3724/SP.J.1006.2017.00149

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The objective of this study was to understand the effect of water deficit onphotosynthetic and assimilate translocation in wheat spike during mid- to late-filling stage by using two pot-cultured¹⁴C-labelled varieties differing in drought tolerance. Under moderate water deficit, the net photosynthetic rate (P_n) of flag leaf and spike at 20 days after anthesis (DAA) decreased by 50.2% and 19.9% in Zhengyin 1 (drought sensitive) and by 33.7% and 12.8% in Pubing 143 (drought tolerance), respectively. Obviously, the decrease of photosynthetic capacity greater in the drought-sensitive variety than in the drought-resistant variety in response to water stress. The ¹⁴C-assimilates accumulated rapidly in grains during 15–20 DAA and reached the peak at 25 DAA. Simultaneously, the ¹⁴C-assimilates in glume, lemma, and awn had a quick outward transportation during 15–20 DAA, and completely transferred to grains at 25 DAA. Compared with normal water condition, moderate water deficit resulted in significantly higher ¹⁴C-assimilates in grains at maturity. The ¹⁴C-assimilate accumulation in Pubing 143 was significantly higher than that in Zhengyin 1, and the yield loss caused by drought stress was 23.2% in Pubing 143 and 36.7% in Zhengyin 1. Compared with drought-sensitive variety, drought-tolerant variety received less influence of moderate water deficit on spike P_n and stronger assimilate translocation from spike bracts to grain. This might be the physiological basis of stable yield in drought-resistant wheat variety.