Table of Content

12 July 2014, Volume 40 Issue 07

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REVIEW

Research Progress in Seed Germination and Its Control

XU Heng-Heng,NI LI,LIU Shu-Jun,WANG Wei-Qing,WANG Wei-Ping,ZHANG Hong,CHENG Hong-Yan,SONG Song-Quan

Acta Agron Sin. 2014, 40(07):  1141-1156.  doi:10.3724/SP.J.1006.2014.01141

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Most flowering plants reproduce through sexual breeding and seed production. The success of seed germination and the establishment of a normal seedling determinate the propagation and survival of plant species. Seed germination is the most critical and flimsy phase in plant life cycle because of its high vulnerability to injury, disease and environmental stress, which are very important especially for annual and biannual plant species. Seed germination is a complex and multistep process during which the quiescent dry seeds quickly recover the metabolic activity, complete essential cellular events for the embryo to emerge from surrounding structures, and prepare for subsequent seedling growth. In the present paper, the recent research progress in seed germination and its control is reviewed, mainly including the important physiological events during germination, the protein synthesis, posttranslational modification and proteome associated with seed germination, and regulation of phytohormone on seed germination. Furthermore, we have also proposed an energy stimulating hypothesis for seed germination, which provides a new idea for answering two fundamental questions in botany, agronomy and horticulture: how does the embryo emerge from its surrounding structures to complete germination, and how is embryo emergence blocked so that seeds can be maintained in the dormant state? and for decreasing the pre-harvest sprouting occurred in seed and foodstuff production of cereal crops.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Function of Acid Insoluble Lignin and GhLaccase in Cotton Resistance to Verticillium Wilt

WU Li-Zhu,WANG Xing-Fen,ZHANG Yan,LI Xi-Huan,ZHANG Gui-Yin,WU Li-Qiang,LI Zhi-Kun,MA Zhi-Ying

Acta Agron Sin. 2014, 40(07):  1157-1163.  doi:10.3724/SP.J.1006.2014.01157

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To search cotton resistance to verticillium wilt, we inoculated Verticillium dahliae into roots of three cotton varieties with different resistance, Pima 90-53, Jimian 20, and Han 208, observed the structure of cell wall, determined the content of lignin and analyzed the transcript level of Laccase. The results showed that, at one day after infection (dpi), the pathogen was unobserved in root vascular tissue of Pima 90-53, while observed in Jimian 20 and Han 208. At 35 days after infection, the cell wall was highly lignified and the vascular was unblocked in Pima90-53, while there were moderately lignified and slightly blocked in Jimian 20, and lowly lignified and seriously blocked in Han208. The contents of acid soluble lignin (ASL) and acid insoluble lignin (AIL) in leaves and petioles of the three cotton varieties planted in the diseased nursery were measured. The results showed that the content of AIL was negatively correlated with the disease index of the three cultivars (r = 0.99991^*), and the cotent ratio of AIL to ASL was in accord with the verticillium wilt resistance of cotton. The transcript level of Laccase was detected using real-time PCR method, the transcription level of GhLaccase in Jimian 20 was significantly higher than that in Han 208 at any point of test time. The expression level reached the highest at 8 h after infection and maintained the high level within three days. So GhLaccase performed high efficiency in response to the infection of Verticillium dahliae. In conclusion, AIL is positively correlated with the verticillium wilt resistance of cotton, and Laccase plays an important role in cotton resistance to Verticillium dahliae.

In silico Expression Profile of Maize Genes in Response to Osmotic Stress

GE Shu-Juan,SUN Ai-Qing,LIU Peng,ZHANG Jie-Dao,DONG Shu-Ting

Acta Agron Sin. 2014, 40(07):  1164-1173.  doi:10.3724/SP.J.1006.2014.01164

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In this study, a germplasm POB21 was used to analyze leaf cDNA library of maize treated with 15% PEG by in silico expression profile. The results indicated the POB21 genome shared significantly high similarity with reference genome. The gene expression in maize transcriptome presented strong nonhomogeneity and partial redundancy. A total of 1097 differentially expressed genes (DEGs) were screened out, of which 795 DEGs were up-regulated and 302 DEGs were down-regulated. GO enrichment analysis of these DEGs showed that three cellular components and three molecular functions of glycosyl transferase activity were enriched. The KEGG pathway analysis showed these DEGs were involved in metabolisms of carbohydrate, protein, nucleic acid, lipid, secondary metabolites, hormones and energy. The DEGs involving in proline metabolism indicated glutamate pathway is the predominant accumulation way of proline under osmotic stress in maize. The result lay a foundation for further study of molecular mechanism in response to osmotic response and functional genes screening of maize.

Cloning and Characterization of Brassica juncea Zinc Finger Protein Transcription Factor Gene Bj26

JIA Shuang-Wei,GAO Ying,ZHAO Kai-Jun

Acta Agron Sin. 2014, 40(07):  1174-1181.  doi:10.3724/SP.J.1006.2014.01174

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Zinc-finger proteins, forming an important transcriptional factor family, are involved in gene transcriptional regulation, development and stress-responses in plants. The previous studies revealed that BjC-P is a fungus-inducible promoter from Brassica juncea and W-box-like-4 is the core element responsive to fungal infection. Here, we report the molecular cloning and characterization of a zinc finger protein-encoding gene (designated Bj26). Bj26 was screened out from the Brassica juncea cDNA library by the Yeast One-Hybrid System. Bioinformatic analysis showed that Bj26 contains open reading frame of 735 bp that encodes a new C2H2-type zinc finger protein with an isoelectric point (pI) of 9.2 and a molecular weight of 26.6 kD. The protein consists of two typical zinc-finger domains and contains two conserved QALGGH amino acid sequences. Subcellular localization showed that Bj26 is located in the nuclear. The histochemical and quantitative GUS assays, through transient gene expression in Nicotiana benthamiana leaf, showed that Bj26 can bind to the core element W-box-like-4 and activate the function of BjC-P. qRT-PCR analysis showed that the gene Bj26 expression obviously increased under the induction of the fungal elicitor (Hexa-N-Acetyl-Chitohexaose). CDS alignments and phylogenetic analysis of Bj26 and other C2H2-type proteins from Arabidopsis thaliana (At) and Oryza sativa (Os) (MEGA 6) showed Bj26 shares high similarity with that from Arabidopsis thaliana (At). All of the above results suggested that Bj26 protein mediates the process of plant response to fungal pathogen.

Identification and Gene Fine Mapping of an Early Senescent Leaf Mutant esl5 in Oryza sativa

SANG Xian-Chun,XU Fang-Fang,ZHU Xiao-Yan,XING Ya-Di,HE Pei-Long,ZHANG Chang-Wei, ANG Zheng-Lin,HE Guang-Hua

Acta Agron Sin. 2014, 40(07):  1182-1189.  doi:10.3724/SP.J.1006.2014.01182

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Premature senility directly influences crop yield and quality in the production. Therefore, it is crucial to identify early senescent leaf mutants and then clone genes associated with senescence by map-based strategy, which is significant in the research of senescence mechanism. An early senescent leaf mutant esl5 has been discovered from the progeny of indica restorer line Jinhui10 with seeds treated by ethylmethane sulfonate, this paper performed the studies on its morphological identification, cytological observation, physiological analysis and gene mapping. The results showed that the esl5 demonstrated normal phenotype at the seedling stage, displayed yellow green color at the tillering stage, and appeared yellow and senescent leaf blades at booting stage. Cell structure ofthe esl5 was badly influenced, showing destroyed cell membranes, loose and irregular stroma lamella in the section of senescent leaves. Chlorophyll content and photosynthetic rate of the esl5 were significantly twice than those of the wild type. Besides of the lower activities of SOD and CAT, the higher contents of ·OH and H₂O₂ were detected in the esl5 than in the wild type. The growth period of esl5 delayed 20 days, seed number per panicle, filled-seed number and seed setting rate increased significantly, but 1000-seed weight increased significantly at compared with the wild type. Genetic analysis suggested that the mutant was controlled by a recessive nuclear gene, and the ESL5 was fine mapped on chromosome 3 between Indel markers Indel03-1 and Indel03-2 with 83.4 kb physical distance, containing 11 annotated genes. These results provide a foundation for the cloning of ESL5 by map-based strategy, which is essential in the research of senescence mechanism as well as molecular breeding in Oryza sativa.

Cloning of New Herbicide Resistant Gene in Soil Metagenomics and the Generation of Transgenic Rice Plants

WANG Yun-Peng,MA Jing-Yong,MA Rui,MA Jian,LIU Wen-Guo

Acta Agron Sin. 2014, 40(07):  1190-1196.  doi:10.3724/SP.J.1006.2014.01190

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The EPSPS, EC 2.5.1.19 (5-enolpyruvylshikimate-3-phosphate synthase) is considered as one of the crucial enzyme in the shikimate pathway for the biosynthesis of essential aromatic amino acids and secondary metabolites in plant. It is also proved as a specific target of broad spectrum herbicide glyphosate. In this research, a new glyphosate resistant EPSPS gene named soilEPSPS was isolated by screening the metagenomic library. The sequence analysis suggested that soilEPSPS consists of 1404 bp and encodes a polypeptide of 467 amino acids that are not involved in the amino acid sequence protected by the published patentsions. The result of prokaryotic expression confirmed that soilEPSPS had a better ability of glyphosate resistance than EPSPS CP4 gene. Fusing the gene and the Rubisco SSU signal peptide constructed the plant expressing vector with the actin promoter driven, and transformation of rice mediated by Agrobacterium tumefaciens. PCR and Southern analyses showed that a total of 26 transgenic plants were obtained and three of them were single copy insertion events. Resistant experiment showed that the homozygous T₂ plants in these events could tolerate the spray of 500 mmol L^-1 glyphosate solution. This study laid a foundation for breeding transgenic herbicide resistant rice varieties.

Correlation of SSR Markers with Agronomic Traits in Peanut (Arachis hypogaea L.)

ZHOU Jin-Chao,YANG Xin-Lei,MU Guo-Jun,CUI Shun-Li,HOU Ming-Yu,CHEN Huan-Ying,LIU Li-Feng*

Acta Agron Sin. 2014, 40(07):  1197-1204.  doi:10.3724/SP.J.1006.2014.01197

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A Recombinant Inbred Line (RIL) population including 251 lines, derived from the cross between Silihong and Jinonghei 3 was used to study the correlations between SSR markers and agronomic traits at two locations of Baoding and Handan, Hebei with Pearson’s correlation and stepwise multiple linear regression analysis. The results showed that there were significant correlations (P≤0.05, P≤0.01) among 18 agronomic traits, with the higher correlations between pod weight per plant and seed weight per plant (r=0.970), as well as the height of main stem and length of first branches (r=0.918). There existed significant correlation between SSR marker and agronomic trait with a average of 2–6 markers correlated with each agronomic trait. Fourteen SSR markers were associated with 13 agronomic traits with explanined phenotypic variances of 5.2%–11.5%. All these laid a solid foundation for peanut conventional breeding and molecular marker-assisted breeding programs.

Isolation and Expression of Mulberry (Morus alba L.) EIN2 Gene

LIU Chang-Ying,Lü Rui-Hua,ZHU Pan-Pan,FAN Wei,LI Jun,WANG Xiao-Hong,LI Zhen-Gang,WANG Xi-Ling,ZHAO Ai-Chun,LU Cheng,YU Mao-De

Acta Agron Sin. 2014, 40(07):  1205-1212.  doi:10.3724/SP.J.1006.2014.01205

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 EIN2 is a central component of ethylene signaling pathway, transferring the ethylene signal from endoplasmic reticulum to nucleus. A putative EIN2 gene obtained from Morus Genome Database and its expression levels were detected by using RT-PCR. The full-length genomic sequence of MaEIN2 is 5614 bp in length, which consists of seven exons and six introns. The CDS of MaEIN2 is 3921 bp and encodes 1036 amino acids. Phylogenetic tree analysis revealed that MaEIN2 had closer relationships with dicotyledons plants and further with monocotyledons plants. The expression levels of MaEIN2 in old leaf and mature fruit were much higher than these in young leaf and immature fruit. The expression levels of MaEIN2 was increasing gradually in fruit development, indicating MaEIN2 was involved in the ripening and senescence of plant organs. Ethephon, ABA and NaCl were used to incubate the mulberry seeds, showing that ethephon induced the expression of MaEIN2 in seedlings, while ABA and NaCl downregulated the expression of MaEIN2. This work lays a foundation for further understanding of the function of MaEIN2.

Development and Universality Evaluation of EST-SSR Markers in Jute (Corchorus spp.) from GenBank Database

ZHANG Li-Wu**,YUAN Min-Hang,HE Xiong-Wei,LIU Xing,FANG Ping-Ping,LIN Li-Hui,TAO Ai-Fen,XU Jian-Tang,QI Jian-Min

Acta Agron Sin. 2014, 40(07):  1213-1219.  doi:10.3724/SP.J.1006.2014.01213

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Developing EST-SSR markers from GenBank Database is important in dissecting genetic base in jute. The aim of this study was to analyze SSR distribution in ESTs of jute, develop new EST-derived SSR markers, and validate polymorphisms of EST-SSR markers in jute. All 838 EST sequences of jute were downloaded from GenBank database. Sixty-six pairs of primers were screened by the software SSRPrimer and designed by the software Primer 3.0. The PCR products of these primers were detected by agarose gel electrophoresis. Polymorphism of six diverse accessions in jute was tested. Among these primers, 42 (63.6%) successfully amplified at least one clear and stable fragment from the jute genome and showed polymorphism between at least two diverse accessions. The polymorphic SSRs contained repeat motifs with (AT)n or (GC-)n, which could be regarded as the dominant motifs in jute. The EST-SSR markers in jute could be developed effectively, which can not only enrich the number of molecular markers, but also dissect genetic basis of important traits in jute.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Metabolism of Reactive Oxygen Species Involved in Increasing Root Vigour of Cotton Seedlings by Soaking Seeds with Mepiquat Chloride

WANG Ning,TIAN Xiao-Li,DUAN Liu-Sheng,YAN Gen-Tu,HUANG Qun,LI Zhao-Hu

Acta Agron Sin. 2014, 40(07):  1220-1226.  doi:10.3724/SP.J.1006.2014.01220

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The plant growth regulator, mepiquat chloride (1,1-dimethylpiperidinium chloride, DPC) has been used worldwide to suppress excessive growth in cotton plants. It also increases the root vigour of cotton plants. To reveal the possible role of reactive oxygen species (ROS) involved, we conducted a experiment to investigate the effect of soaking seed with 200 mg L^–1 mepiquat chloride (DPC) on root vigour of cotton (Gossypium hirsutum L.) seedlings by using a cotton cv. Guoxin 3. The results showed that soaking seed with DPC could significantly increase the root vigour of cotton seedlings with two expanded cotyledons.Root viability estimated by 2,3,5-triphenyl tetrazolium chloride (TTC) reduction and root respiratory rate were increased by 167% and 90% in DPC treatment. The average OD of in situ TTC staining in DPC treated root tips was 0.3-fold higher than that of control. At 300 μm from the root apex away, DPC treatment resulted in a 36% increase of net K⁺ influx. The result of acridine orange staining suggested that seedlings treated with DPC had less apoptotic cells in root elongation zone compared with control. In addition, DPC treatment significantly altered the activities of antioxidant enzyme and ROS accumulation in roots of cotton seedlings. Catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were enhanced, but superoxide dismutase (SOD) was reduced, which therefore resulted in 56% less H₂O₂ accumulation and lighter diaminobenzidine staining (H₂O₂ histochemical detection in situ) in roots compared with control. Another type of ROS, O₂⁻, its production rate also decreased by 65% in roots treated with DPC. Taken together, we speculated that the increased root vigour of cotton seedlings by soaking seed with DPC may be partially explained by improvement of ROS metabolism.

Variation of Provitamin A and Vitamin E Components at Milk Stage of Kernel Development in Sweet Corn

FENG Fa-Qiang,WANG Guo-Hua,WANG Qing-Feng,YANG Rui-Chun,LI Xiao-Qin

Acta Agron Sin. 2014, 40(07):  1227-1234.  doi:10.3724/SP.J.1006.2014.01227

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Vitamin A and Vitamin E are two kinks of micronutrients that must be acquired regularly from dietary sources. Sweet corn is a type of fresh corn for direct consumption by human beings. The content of provitamin A and vitamin E components at milk stage of kernels development were measured by HPLC in 47 sweet corn lines. The results showed that the contents of carotenoids and tocopherols and the α/γ tocopherol ratio were extremely different among 47 sweet corn lines. The non-provitamin A, including lutein and zeaxanthin, is the main components of the total carotenoids. The main component of vitamin E is γ-tocopherol. The pearson correlation analysis showed that significantly positive correlation and non-correlation were detected among most traits. β-Carotene was significantly positive correlated with zeaxanthin, β-cryptoxanthin and α-carotenoids, respectively. Three isomers of vitamin E were significantly correlated between each other. The ratio of α/γ tocopherol had a significantly negative correlation with δ-tocopherol and γ-tocopherol and a significantly positive correlation with zeaxanthin and α-tocopherol. A significantly positive association was found between β-carotene and α-tocopherol. These results provide useful information for the research on provitamin A and vitamin E metabolism and nutritional improvement in sweet corn.

Effects of Light, Nitrogen and Their Interaction on Grain Yield and Nitrogen, Phosphorus and Potassium Absorption in Japonica Super Rice

WANG Ya-Jiang,WEI Hai-Yan*,YAN Xi-Ting,GE Meng-Jie,MENG Tian-Yao,ZHANG Hong-Cheng,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,FEI Xin-Ru

Acta Agron Sin. 2014, 40(07):  1235-1244.  doi:10.3724/SP.J.1006.2014.01235

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A field experiment was conducted using japonica super rice Nanjing 44 and Ningjing 3 with two nitrogen fertilization levels (N10: 150 kg ha^-1, N20: 300 kg ha^-1) and three shading treatments (L1: no shading, L2: shading 20 days before heading, L3: shading 20 days after heading) to study theeffects of light, nitrogen and their interaction on grain yield and NPK absorption. Results showed that yield under the same level of nitrogen fertilizer was L1>L3>L2. Compared with L1, L2 significantly reduced NPK accumulation from jointing to heading and at whole heading stage, mainly due to the significant decrease of the root oxidation ability of α-NA and root dry weight before heading, resulting in decreased root nutrient uptake capacity and the final yield decrease of 30.58%–35.26%. L3 significantly reduced NPK accumulation from heading to maturity and at whole maturity stage, mainly due to the significant decrease of the root oxidation ability of α-NA and root dry weight after heading. Although the root was gradual aging with the function declining after heading, resulting in the reducedeffect onroot system, nutrient absorption and yield in L3 than in L2, the final yield was still 10.91%–18.47% lower in L3 than in L1. Under L2 and L3 conditions, with increasing nitrogen level, the root oxidation ability of α-NA and root dry weight increased significantly, resulting in that NPK accumulation increased significantly in various stages from jointing to maturity, then the final yield and nitrogen use efficiency improved significantly. This indicated that nitrogen fertilizer could partially offset the impact of low light stress on NPK nutrient absorption and grain yield in japonica super rice.

Effects of Cultivation Patterns on Root Morph-physiological Traits and Aboveground Development of Japonica Hybrid Rice Cultivar Changyou 5

CHU Guang,ZHOU Qun,XUE Ya-Guang,YAN Xiao-Yuan,LIU Li-Jun,YANG Jian-Chang

Acta Agron Sin. 2014, 40(07):  1245-1258.  doi:10.3724/SP.J.1006.2014.01245

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The objective of this study was to investigate if a cultivation technique could coordinately increase both grain yield and nutrient use efficiency of rice through an improvement in morphological and physiological traits of roots. A field experiment was conducted using japonica hybrid rice cultivar Changyou 5 with four cultivation patterns including no nitrogen application (0N), local high yielding cultivation (control), super high yielding cultivation (SHY) and high nutrient use efficiency cultivation (HUEN) .The results showed that, the grain yield was 12.29 t ha^-1 under SHY and 9.62 t ha^-1 under HUEN, which was 41.4% and 10.7% higher than that under the control, on the average, respectively. When compared with the control, SHY and HUEN increased nitrogen (N) agronomic efficiency (the increase in grain yield divides by the amount of N application) by 80.6% and 76.8%, and irrigation water use efficiency by 62.1% and 32.3%, respectively. The SHY and HUEN also significantly increased biomass from heading to maturity, leaf area index, root dry weight and root length, grain-leaf ratio, root-shoot ratio, the amount of root bleeding, photosynthetic rate of the flag leaf, root oxidation activity, total absorbing surface area and active absorbing surface area, contents of cytokinins (zeatin + zeatin riboside) in roots, leaves and root bleedings, and activities of sucrose synthase and adenosine diphosphate-glucose pyrophosphorylase in grains during grain filling. The results indicate that higher grain yield and high nutrient and water use efficiencies can be coordinately achieved through using integrating and optimizing cultivation techniques in rice production.

Comprehensive Valuation of Drought Resistance and Screening of Indices of Important Flax Cultivars

LUO Jun-Jie,OU Qiao-Ming,YE Chun-Lei,WANG Fang,WANG Yong-Zhen,CHEN Yu-Liang

Acta Agron Sin. 2014, 40(07):  1259-1273.  doi:10.3724/SP.J.1006.2014.01259

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Seven main agronomic traits, eight physiological indices and yield index of 15 main flax cultivars in China were measured during maturity under the conditions of irrigation and natural rainfall. Comprehensive drought resistance coefficient (CDC value), factor analysis, subordinate function coefficients, clustering analysis, grey relational analysis were used to evaluate the drought resistance, classify drought resistance type and select evaluation indices in tested flax cultivars. The response to drought stress and correlations of tested traits and indices were different. Yield and photosynthesis factors as well as leaf antioxidant factors were closely associated with drought resistance, so could be used as priority indicator of drought resistance evaluation. Factor analysis showed that six common factors could represent 90.89% of the original information of flax drought resistance data. The ranks of drought resistance of tested flax cultivars based on drought resistance comprehensive evaluation values (D value) and weight drought resistance coefficient (WDC value) were similar, the drought resistance was the same for six flax cultivars, arranging from the first to third in drought resistance. D values of tested flax cultivars had significant and positive correlation with CDC value, WDC value and Y value. Y values of tested flax cultivars also had very significant and positive correlation with CDC value and WDC value. According to D value clustering analysis, tested cultivars were divided into five grades in drought resistance, reflecting the diffirence of cultivars in breeding condition and adaptive region growing well. Drought resistance evaluated mainly with yield by D value as index and WDC value as auxiliary index in flax were appropriate and accurate. Drought resistance comprehensive evaluation methods can be used in studying exactly drought resistance evaluation, classification of drought resistant type and screening evaluation indices in flax.

Effects of Continuous Cropping on Dry Matter Accumulation and Distribution of Potato Plants in Yellow River Irrigation Areas of Middle Gansu Province

LIU Xing,Zhang Shu-Le,Liu Guo-Feng,QIU Hui-Zhen,WANG Di,ZHANG Jun-Lian,SHEN Qi-Rong

Acta Agron Sin. 2014, 40(07):  1274-1285.  doi:10.3724/SP.J.1006.2014.01274

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The Yellow River irrigation areas of middle Gansu Province is one of the major growing regions of processing potato in China and potato is often planted continuously by farmers eager to maximize profit, this practice results in the severe decline in tuber yield and also affects the healthy development of the potato industry locally. It is necessary to explore effects of continuous cropping on potato yield formation. On the basis of the long-term experiment, with taking filed cropping six potato cropping treatments, corresponding to continuously planted potato crop over 0–5 years respectively, we made an attempt to understand the effects of continuous cropping on potato tuber yield, dry matter accumulation and distribution, and accumulation and translocation of dry matter during post-anthesis. There were no statistical differences in tuber yield under the short-term continuous cropping compared with control, however, significant decline in tuber yield by 21.68%–75.67% occurred after three years of continuous cropping, which was mainly derived from the decline in the average fresh-weight of individual tuber. Dynamics of dry matter accumulation in the whole plant and tuber both showed the “S” curve feature, and the continuous cropping decreased the average rate and the duration in dry matter accumulation during quickly accumulative period of potato compared with control. The continuous cropping also affected dry matter distribution, especially increased dry matter distribution ratio in root compared with control. For tuber yield formation, the long-term continuous cropping increased the contribution of translocation of dry matter stored in vegetative organs during pre-anthesis, whereas decreased the contribution of direct assimilate accumulation in tuber during post-anthesis. In conclusion, the long-term continuous cropping leeds to an imbalance of sink-source relationship of potato plants, which is the main cause of tuber yield decline.

Effect of Subsoiling in Fallow Period and Nitrogen Application on Soil Moisture and Grain Protein Accumulation in Dryland Wheat

SUN Min,GAO Zhi-Qiang*,ZHAO Wei-Feng,REN Ai-Xia,Deng Yan,MIAO Guo-Yuan

Acta Agron Sin. 2014, 40(07):  1286-1295.  doi:10.3724/SP.J.1006.2014.01286

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The objective of this study was to explore a technique to increase and maintain soil moisture of dryland through subsoiling during fallow period (SS) and the proper nitrogen (N) application in wheat production. In a two-year field experiment carried out in Wenxi County of Shanxi Province, China from autumn 2009 to summer 2011, we tested soil moistures in different soil layers, protein content and its components in grain, and activities of enzymes related to protein accumulation during grain filling after SS and non-tillage practice (CK) in combination with the applications of low (LN, 75 kg ha^-1), medium (MN, 150 kg ha^-1), or high (HN, 225 kg ha^-1) N. Before sowing, the soil moistures in 0-300 cm soil layers under SS condition were higher than those under CK condition, especially in 60–160 cm soil layers, which were increased by 12%–34% in dry year and 10%–22% in humid year. Under SS condition, the activities of protein-related enzymes increased, such as glutamine synthetase (GS) in grain, glutamate synthase (GOGAT) in flag leaf, and GOGAT in grain in LN and MN treatments, and glutamic acid-pyruvate transaminase (GPT) in grain. In mature grains, the globulin content and protein yield in SS treatment were increased compared with CK, and Glutenin content and glutenin/gliadin ratio in humid year also increased in SS. The soil moisture in 20–200 cm soil layer at anthesis stage showed a decrease trend with the increase of nitrogen application level; however, the GS activity in grain, GOGAT activity in flag leaf at middle to late filling stage , GPT activity in grain at late filling stage were enhanced, and the contents of protein and its components in grain were increased. The glutenin/gliadin ratio in grain was the highest in MN treatment. Nitrogen application had obvious effects on soil moisture in the deep soil layer at anthesis, also on protein yield, GS and GPT activities in grain under SS condition. Under SS plus N application condition, soil moisture at anthesis was closely correlated with grain albumin, glutenin, and protein content in humid year and with glutenin/gliadin ratio in dry year. In conclusion, subsoiling during fallow period is an effective method to maintain soil moisture in dryland; N application at 225 kg ha^-1 has a positive effect on increasing contents of grain protein and its components, whereas N level of 150 kg ha^-1 is favorable for high protein yield and glutenin/gliadin ratio in grain in dry year.

Improvement of Hybridization Success Rate in Soybean from Northeast China during Winter Nursing in Hainan Island

ZHANG Yong,SUN Shi,YANG Xing-Yong,SUN Xue-Gang,WU Cun-Xiang,HAN Tian-Fu

Acta Agron Sin. 2014, 40(07):  1296-1303.  doi:10.3724/SP.J.1006.2014.01296

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To accelerate the soybean breeding progress and to broaden the genetic basis of new varieties, it is necessary to improve the hybrid seed-setting rate of soybean during winter nursing. Seven early-maturing soybean varieties from northeast China were selected in hybridization experiments with photoperiod treatments in Sanya, Hainan, China. Morphological traits, growth and development periods, floral organ characteristics and pollen fertility were observed or documented under long day (LD, 18 h) treatment and normal short day (NSD) conditions, respectively. At the same time, the effects of light treatment, emasculation of the female parent, and flower bud size on the hybridization were investigated. The results showed that under the NSD environment in Sanya, the flowering period and plant height shortened, the flower number and single floral weight decreased, the flower and its constituents became smaller, and the pollen sterility rate increased (P<0.01) as compared with those under LD treatment (P<0.01), Taking the plants with big flower bud under NSD as the female parent, and the plants under LD treatment as the male parent, we made the crosses and pollinated without emasculation, with the hybrid seed-setting rate of 64.36%, which is high enough for breeding purpose. According to the results, we propose the solution for improving the hybrid success rate of soybean in winter nursery.

RESEARCH NOTES

Cloning and Expression Analysis of Two Homologous Genes Coding sn-Glycerol-3-Phosphate Acyltransferase 6 in Brassica napus

LIU Cong,XIAO Dan-Wang,HU Xue-Fang,WU Ke-Bin,GUAN Chun-Yun,XIONG Xing-Hua

Acta Agron Sin. 2014, 40(07):  1304-1310.  doi:10.3724/SP.J.1006.2014.01304

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A key enzyme sn-glycerol-3-phosphate acyltransferase (GPAT) catalyzes the initial step of TAG biosynthetic pathway, and is involved in many processes including plant growth, development and response to abiotic stresses. In this study, two B. napus GPAT6 homologs were cloned from the leaf of the cultivar xiangyou 15 using RT-PCR, and designated as BnGPAT6-1 and BnGPAT6-2, respectively. The coding DNA sequences (CDS) of two BnGPAT6 genes are 1506 bp in length, encoding two different polypeptides of 501 amino acid residues. The proteins were predicted to consist of a haloacid dehalogenase-like hydrolase domain and a lysophospholipid acyltransferase domain. Multiple sequence alignments and phylogenetic analysis of GPAT proteins showed that BnGPAT6-1 and BnGPAT6-2 share high similarity with GPAT6 genes from B. rapa, B. oleracea, Arabidopsis thaliana,and A. lyrata. Tissue expression amounts of BnGPAT6 genes showed that their mRNA were more abundant in flower than the other organs, and the patterns rise up at first and then down in the developing embryo. The expression of BnGPAT6 genes are inhibited by ABA, while go up simultaneously under drought and 6-BA conditions. In the treatment of salt, the expression of BnGPAT6 genes are uptrend in a short time and then down, and there isn’t obvious change under stress of water logging.

Genetic Diversity Analysis of Germplasm Resources and Construction of Mini-core Collections for Vicia faba L. at Home and Abroad

JIANG Jun-Ye,YANG Tao,WANG Fang,FANG Li,ZHONG Wei-Wen,GUAN Jian-Ping,ZONG Xu-Xiao

Acta Agron Sin. 2014, 40(07):  1311-1319.  doi:10.3724/SP.J.1006.2014.01311

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The genetic diversity of 1075 genotypes from a primary geographic core collection of faba bean (Vicia faba L.) was analyzed by using SSR markers. The number of observed and effective alleles of 8.54 and 2.26, the Shannon’s information index of 1.02, were detected. Unconspicuous population structure among the 1075 genotypes indicated an extensive genetic background and nice representativeness. A mini-core collection comprised 129 Chinese and 63 oversea faba bean genotypes was randomly sampled from each cluster of dendrogram including all the 1075 tested genotypes. The observed alleles, effective alleles and Shannon’s information index of the mini-core collection covered 87.32%, 101.26%, and 101.82% that of primary geographic core collection respectively. The t-test did not show significant differences in genetic diversity between the primary geographic core collection and the mini-core collection, which validated the representativeness of the mini-core collection in genetic diversity of faba bean. The mini-core collection will play an important role in exploration of new genes within faba bean.

Changes of Safe Production Dates of Double-season Rice in Middle Reach of the Yangtze River

AI Zhi-Yong,GUO Xia-Yu,LIU Wen-Xiang,MA Guo-Hui，QING Xian-Guo

Acta Agron Sin. 2014, 40(07):  1320-1329.  doi:10.3724/SP.J.1006.2014.01320

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Safe production date is an important basis for variety and planting pattern selections, high use efficiency of heat and light resources, and production season safety. In this study, the daily average temperatures during the 50 years (1960–2009) provided by 47 meteorological stations in Middle Reach of the Yangtze River were analyzed, and several safe production dates for double-season rice with 50% and 80% guarantee rates were provided. Among the safe dates with 80% guarantee rate which were used generally in double-season rice production, the safe sowing date of early-season rice seedlings raised in dry nursery covered with film was three days later, that in wet nursery without covering was three days earlier, the safe transplanting date of early-season rice was four days earlier, the safe full heading date of late-season hybrid indica rice was three days earlier, and that of late-season inbred indica rice was one day later, the days of safe growth season of the double-season rice whose early-season rice seedlings raised in dry nursery covered with film were four days shorter, those in wet nursery without covering were one day longer during the second 25 years than during the first 25 years, and safe maturity date of late-season rice between the first and the second 25 years was not changed. In this paper safe production dates with 80% guarantee rate from each meteorological station during the second 25 years were proposed, which could be utilized as a references for production season arrangement, variety and planting pattern selections in double-season rice production according to the nearest guiding principles. The changes of climate and safe production date were not more significant in middle reach of the Yangtze River than in the Northeast and the North China. The clear advance of safe sowing date of early-season rice seedlings raised in wet nursery without covering and safe transplanting date of early-season rice was advantageous to move seeding date forward and improve yield potential for early-season rice. Changes of other safe dates were disadvantageous to prolong growth season and increase yield potential, even have a small advance for full heading date of late-season rice. Consequently, from the perspective of production safety, the direct-seeding rice should not be generalized blindly, for the machine-transplanting rice more attention should be paid to safe production date, suitable variety selection and sowing date arrangement in this area.