Table of Content

12 May 2011, Volume 37 Issue 05

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Improving the Resistance of Wuyunjing 8 to Rice Stripe Virus via Molecular Marker-Assisted Selection

ZHANG Hong-Gen, HU Zuo-Peng, LI Peng, LI Bo, LIU Chao, ZHU Bang-Hui, XU Ji-Fen, CHOU Zhong-Yi, TANG Shu-Zhu, LIANG Guo-Hua, GU Ming-Hong

Acta Agron Sin. 2011, 37(05):  745-754.  doi:10.3724/SP.J.1006.2011.00745

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In this study, a molecular marker-assisted selection (MAS) strategy was used to improve Wuyunjing 8’s resistance to rice stripe virus. The Wuyunjing 8 with high yield and erect head selected from 25 late-maturing varieties was used as accepter, and the variety Kuifeng with resistance to rice stripe virus as the donor. Four STS (sequence-tagged site) primers STS11-31, STS11-7, STS11-19, and STS11-43 anchoring the resistance genes were used for assisted selection in the backcross progenies. To 2008, seventy lines in BC₃F₅ and one hundred and fifteen lines of BC₄F₄ with stable agronomic traits were obtained with the result of molecular analysis. By appraising agronomic traits，yield , quality and resistance in backcross progenies, teen lines from BC₄F₅ and two lines from BC₃F₆, which all carried disease-resistant genes and were similar to Wuyunjing 8 on the integrated traits, were selected. These lines retain the characteristics of high yield and good quality of Wuyunjing 8 and have been prominently improved in resistance to rice stripe virus.

Development and Application of a Computer-Aided Selection System for Thermo-Sensitive Genic Male Sterile Rice Multiplying Site

LIU Hai, XIAO Ying-Hui, TANG Wen-Bang, DENG Hua-Bing, CHEN Li-Yun

Acta Agron Sin. 2011, 37(05):  755-763.  doi:10.3724/SP.J.1006.2011.00755

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Great success has been achieved in the utilization of two-line hybrid rice in China. Nevertheless, the seed production of two-line hybrid rice is still a key technology that limited the extension of two-line hybrid rice on large scale. Seed multiplication of the thermo-sensitive genic male sterile (TGMS) rice, which with a narrow range of temperature for fertility restoration, is hard to be success by using the most common multiplying technologies currently. In order to improve the yield stability and security in TGMS rice multiplication, we developed a practical computer selection system for choosing an optimal multiplying site. This system using the java language was able to select suitable multiplying sites with optimal ecological factors which meet the requirement of the fertility sensitive stage (FSS) and heading-flowering stage (HFS) for TGMS rice multiplication. By using this computer-aided selection system, 24, 29, 20, 21, and 22 ecological areas were selected ,which were superior to the most common seed producing area, Sanya of Hainan province, where the suitable probabilities of FSS and HFS are 35.0%, 42.5%, 55.0%, 65.0%, and 75.0% for the TGMS with the critical temperature of 22.0℃, 22.5℃, 23.0℃, 23.5℃, and 24.0℃, respectively, while the suitable probability of the optimal multiplying site selected by the computer-aided selection system were 83%, 93%, 100%, 100%, and 100% in both FSS and HFS for TGMS with different critical temperature, respectively, showing much higher values than those in Sanya, Hainan Province. In 2010, we tried to produce the seed of C815S, a TGMS rice with the critical temperature of 22.0℃ in Baoshan, Yunnan Province selected by the computer-aided selection system. The grain yield reached 8 437.5 kg ha^-1, and created the highest yield record of seed multiplication of the TGMS rice. These results suggested that the problems of unstable yield and low security for the TGMS rice seed multiplication should be solved by this computer aided selection system, and we believe the optimal multiplying site selected by the computer-aided selection system will provide a useful technical support for healthy and sustainable development in the two-line hybrid rice.

Isolation of NBS-LRR Late Blight Resistance Genes from Potato BAC Library by System of Magnetic Separation

XU Jian-Fei, JIN Li-Peng, PANG Wan-Fu, BIAN Chun-Song, DUAN Chao-Guang, LIU Jie, HUANG San-Wen, QU Dong-Yu

Acta Agron Sin. 2011, 37(05):  764-771.  doi:10.3724/SP.J.1006.2011.00764

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Cultivated potato (Solanum tuberosum) is an auto-tetraploid crop, which is very difficult to isolate late blight resistance genes. Nevertheless, it is discovered that there is conseved NBS-LRR domain among late blight resistance genes. In this study, conserved probes of R3a late blight resistance genes family were developed by alignment of sequences. And then, the DNA of BAC SH23G23 containingthe R3a gene was partially digested into 7–11 kb fragments. By magnetic separation system combined with conserved probes, the 7–11 kb fragments were enriched and cloned into binary vector pBINPLUS. Through identification of positive clones and colony PCR, the ratio of clones including R3a gene to all positive clones reached 82.76%, which was nearly 19 times higher than enrichment before. The system of magnetic separation for R genes and their analogs established in this study provides a new strategy for conserved domain genes cloning from polyploid crops.

Genome-wide Analysis of MuDR-related Transposable Elements Insertion Population in Maize

FENG Jing, FU Hua-Gan, WANG Ting-Ting, DAO Yong-Sheng, GAO You-Jun, ZHENG Yong-Lian

Acta Agron Sin. 2011, 37(05):  772-777.  doi:10.3724/SP.J.1006.2011.00772

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Insertional mutagenesis has now been widely used to knockout genes for functional genomics. The maize Mutator transposons hold an advantage of high activity to construct large mutant libraries. In this study, a MuDR line was used to cross with an elite Chinese maize inbred line Z31. A total of 1000 M1 individuals were planted and self-pollinated to generatetheir M2 families. Experiments were conducted to investigate the insertion specificity of MuDR related transposable elements. Six hundred and ninety-five MuDR inserted flanking sequences were isolated with a modified MuTAIL-PCR method and analyzedwith bioinformatics. Three hundred and seventy-four non-redundant insertion sites were identified and 298 of them were mapped to a single locus on the integrated maize map. The results revealed some prominent features of the MuDR-related insertions of maize: random distribution across the 10 chromosomes, preferential insertion into genic sequence and favoring some classes of functional genes.

Analysis of Quantitative Trait Loci for Resistance to Rice False Smut

LI Yu-Sheng, HUANG Sheng-Dong, YANG Juan, WANG Cai-Lin

Acta Agron Sin. 2011, 37(05):  778-783.  doi:10.3724/SP.J.1006.2011.00778

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A recombinant inbred line(RILs) population with 157 lines derived from an inter-subspecies cross of Daguandao/IR28 by the single seed descent method was used to detect quantitative trait loci (QTLs) conferring resistance to rice false smut [caused by U stilaginoidea virens (Cooke) Takahashi] in 2007 and 2009. The disease rate index of the two parents and 157 RILs caused by rice false smut were scored and the QTLs for rice false smut resistance were detected accordingly by QTL Cartographer software. Seven QTLs controlling false smut resistance were detected on chromosomes 1, 2, 4, 8, 10, 11, and 12, respectively, with the phenotypic variance of 9.8%–22.5%. There were five and four QTLs detected in 2007 and 2009, respectively, and only two QTLs were found in both two years, the phenotypic variation was explained by individual QTL ranged from 18.0% to 19.3% for these two QTLs,and the additive effects of these two QTLs contributed to the 8.0%–16.5% decrease of disease index and therefore the disease resistance increased. The direction of the additive effects at six loci qFsr1, qFsr2, qFsr8, qFsr10, qFsr11, and qFsr12 coincided with that predicted by phenotypes of the parents, and the IR28 alleles at these loci had positive effect against rice false smut while the negative effects were found in Daguandao alleles at qFsr4. Both qFsr11 and qFsr12 should be useful in rice breeding for resistance to rice false smut in marker-assisted selection (MAS) program.

Identification of QTLs for Grain Traits in Rice Using Extreme Materials in Grain Size

ZHANG Qiang, YAO Guo-Xin, HU An-Long, TANG Bei, CHEN Chao, LI Zi-Chao

Acta Agron Sin. 2011, 37(05):  784-792.  doi:10.3724/SP.J.1006.2011.00784

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The grain length (GL), grain width (GW), grain thickness (GT), ratio of grain length to width (RLW), and 1000-grain weight (TGW) were evaluated in Beijing. Using a BC₂F₂ population including 216 lines derived from a backcross combination between GSL156 with large grain (71.9 g) and Chuanqi with small grain (12.1 g). The quantitative trait loci (QTLs) for above five grain traits were identified by composite interval mapping using SSR markers. The results showed that the five grain traits exhibited a normal continuous distribution in BC₂F₂ population, indicating that they were quantitative traits controlled by multiple genes. A total of 28 QTLs conferring the five grain traits were detected on chromosomes 1, 2, 3, 4, 5, 6, and 12, respectively. Fourteen QTLs, namely qGL3-2, qGL3-3, qGT12-1, qGT2-1, qGT5-1, qGW1-1, qGW12-1, qGW2-1, qGW5-1, qRLW3-1, qTGW12-1, qTGW2-1, qTGW3-3,and qTGW5-1, were main-effect QTLs and explained 13.70%, 52.51%, 21.13%, 18.79%, 20.92%, 14.59%, 18.33%, 30.03%, 20.05%, 24.53%, 13.47%, 11.43%, 21.30%, and 15.68% of the observed phenotypic variance, respectively. Among them, most QTLs were mapped on chromosome 3. Six QTLs had the alleles contributing to positive effect which were derived from small grain parent Chuanqi while the other 22 QTLs alleles from large grain parent GSL156. The modes of gene action were mainly additive or partial dominance. The marker interval RM7580–RM8208 on chromosome 3 was common to the three QTLs for GW, RLW, and TGW, respectively. The marker interval, RM7636–RM5812 on chromosome 2, RM3351–RM26 on chromosome 5, and RM1103–RM17 on chromosome 12, were common to the three major QTLs, which were associated with GW, GT and TGW, respectively.The eight SSR markers used in this study would be useful in molecular breeding in rice. The alleles from parent with larger grain were showed significant effects on GL, GW, GT, and TGW.

Root Infection and Systematic Colonization of DsRed-labelled Fusarium verticillioides in Maize

WU Lei, WANG Xiao-Ming, XU Rong-Qi, LI Hong-Jie

Acta Agron Sin. 2011, 37(05):  793-802.  doi:10.3724/SP.J.1006.2011.00793

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Fusarium verticillioides (Sacc.) Nirenberg [syn. F. moniliforme J. Sheld., teleomorph: Gibberella fujikuroi (Sawada) Ito in Ito & K. Kimura] is an important causal agent of diseases in maize (Zea mays L.) worldwide, which invades maize plants at all growth stages. This filamentous fungus not only incites obvious symptoms on maize ear, stem, root, and seedling, but also is able to infect plants without any visible symptom (endophytic infection). This makes difficult to detect interaction between this fungus and its hosts.Fluorescent reporter gene-labelled filamentous fungus permits in vitro and in planta monitoring growth and development of the fungus. In this study, gene DsRed encoding red fluorescent protein was delivered into F. verticillioides strain Fv-1 via Agrobacterium tumefaciens-mediated transformation. Using the DsRed-tagged F. verticillioides, systemic colonization of the fungus in roots and stems of the susceptible maize inbred line B73 was investigated. The aim of this study was to understand the interaction between F. verticillioides and maize. The fungus invaded and multiplied inside the lateral root tissues. Some conidia tended to colonize on the veins of the maize root surface and grew along the veins after their germinaiton. Others penetrated the plant cells where they attached and formed hyphae for attacking other cells nearby. Usually, the mycelia migrated from root to stem through intercellular parts of tissues, while some mycelia run across different host cells. Analysis of colony forming unit (CFU) from diseased plants demonstrated that following inoculation the CFU values from roots tended to decrease, but those from stems inclined to increase. This indicates that F. verticillioides is able to attack the aboveground parts of plant via systemic colonization on roots. The results from the present study are useful in disclosing the interaction between F. verticillioides and maize, and can be extended to studying interactions between other soil-borne fungi and plants.

Screening and Identification of Proteins Interacting with ERF Transcription Factor W17 in Wheat

QIU Zhi-Gang, XU Zhao-Shi, ZHENG Tian-Hui, LI Lian-Cheng, CHEN Ming, MA Wei-Zhi

Acta Agron Sin. 2011, 37(05):  803-810.  doi:10.3724/SP.J.1006.2011.00803

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Ethylene responsive factors (ERFs) regulate a variety of biotic- and abiotic-stress responses. Transcription factor W17 is an ERF isolated from wheat (Triticum aestivum L.), which participates in stress responses. To provide data for exploring the functional mechanism of ERF proteins, we constructed a wheat cDNA library and screened proteins interacting with W17 by yeast two-hybrid system. The mixture of recombinant plasmid pGBKT7-W17, pGADT7, and wheat cDNA library was introduced into yeast cell AH109. Transformed cells were incubated on SD/–Trp/–Leu/–His/–Ade plate for 3–5 d at 30℃ before selection of clones with diameter larger than 2 mm, and further incubated on SD/Raf/Gal/x-gal for screening blue clones. Four types of proteins that interacted with W17 were obtained, namely stress-related functional protein, post-translational modification protein, ribulose-1,5-bisphosphate carboxylase/oxygenase, and unknown protein. The protein–protein interaction was retested using the co-transformation yeast system of pGBKT7-W17 and candidates of interaction protein carried by pGADT7. The result showed that Hsp90 and PPR proteins interacted with W17 in vivo. Most of candidate proteins involved in signal transduction and immune process, such as Tir cytoskeleton coupling protein (TCCP), 26S proteasome subunit, RNA binding protein, WD40, PPR, HSP90, and cysteine proteinase inhibitor. This result suggests that W17 possibly plays significant roles in stress signal transduction, transcription regulation of downstream genes, and translation process in stress environments.

Analysis of Genetic Diversity of Major Sugar Beet Varieties from Three Regions of China with SRAP Markers

WANG Mao-Qian, WU Ze-Dong, WANG Hua-Zhong

Acta Agron Sin. 2011, 37(05):  811-819.  doi:10.3724/SP.J.1006.2011.00811

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Shortage ofsugar beet germlasm resources results in the lag in researches of breeding and molecular biology. It is necessary to analyze the major varieties from three major production regions of China. Eighty-eight primer pairs were used to amplify the genomic DNA from leaves of four types of sugar beet varieties with different economic traits, which contain high yield type; high yield, low sugar and Rhizomania resistant type; standard type; medium yield, high sugar and anti-brown spot type, and 33 of which were obtained to be with availability. Two hundred and forty-one varieties from three major regions of China and nine varieties from abroad were detected with 33 primer pairs of SRAP markers. A total of 719 unambiguous bands were obtained, 459 of which were polymorphic. The average ratio of polymorphic bands was 63.8%. Compute over-all mean showed that genetic distance was 0.4165, genetic similarity among varieties was 0.6593, the genetic similarities were 0.7528 among foreign varieties, 0.6945 among monogerm varieties, 0.6816 among polygerm tetraploid varieties, and 0.6612 among polygerm diploid varieties. A total of 250 varieties were divided into four cluster groups based on cluster analysis by MEGA3.1 (at intercept of 0.2). Each genepool from three major region showed the highest. The varieties from China and abroad were classified into two different groups by POPGEN32. This indicated definite difference in the genetic background between foreign and native varieties.s of sugar beet production in China showed high level of genetic diversity, of which the Northeast genepool

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Protein Response of Rice Leaves to High Temperature Stress and Its Difference of Genotypes at Different Growth Stage

ZHOU Wei-Hui, XUE Da-Wei, ZHANG Guo-Beng

Acta Agron Sin. 2011, 37(05):  820-831.  doi:10.3724/SP.J.1006.2011.00820

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High temperature has become a major disastrous factor affecting rice productivity, and the temperature stress becomes more severe due to the global warming effect. The present study was carried out to identify the rice genotypes with high heat tolerance and understand the tolerant mechanisms of both physiology and proteomics. The results showed that seed setting rate, SPAD value, plant height, root length and biomass were dramatically reduced under high temperature, while contents of malondialdehyde, hydrogen peroxide and superoxide anions, and activity of superoxide dismutase were greatly increased, irrespectively of growth stage. Moreover, Minghui 63 (a heat-sensitive genotype) was much more affected by heat stress than Milyang 46 (a heat-tolerant genotype). Proteomic analysis showed that high temperature resulted in down-regulation of the proteins related to photosynthesis, energy and metabolism, while resistance-related proteins were up-regulated. The results also confirmed the heat tolerance of Milyang 46 and the heat sensitivity of the rice plants at heading stage. The up-regulation of anti-stress protein, 2-cys peroxiredoxin BAS1, under heat stress was first reported in this study.

Effects of Asymmetric Warming on Grain Quality and Related Key Enzymes Activities for Japonica Rice (Nanjing 44) under FATI Facility

DONG Wen-Jun, TIAN Yun-Lu, ZHANG Ban, CHEN Jin, ZHANG Wei-Jian

Acta Agron Sin. 2011, 37(05):  832-841.  doi:10.3724/SP.J.1006.2011.00832

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Climate warming presents significantly asymmetric trends with greatly diurnal differences, greater temperature elevations existing for the daily mean minimum temperature than for the daily mean maximum temperature. So far, the evidence is lacking for the effects of asymmetric warming on grain quality of single cropping rice based on field experiments. We performed field warming experiment under Free Air Temperature Increased (FATI) facility to investigate the impacts of asymmetric warming on grain quality and activities of key enzymes of single cropping rice in 2008 in Nanjing city, Jiangsu province, China. The results showed that the all-day warming (AW), daytime warming (DW) and nighttime warming (NW) treatments obviously advanced the grain filling and seed setting stage and changed the beginning date and the duration of high temperature above 35°C in the stage of grain filling, consequently resulting in obvious changes of head rice rate, chalky grain rate, chalkiness, RVA characteristics, starch content and its components, protein content and the activities of key enzymes for starch and protein syntheses. All the treatments decreased significantly head rice rate, increased significantly chalky grain rate and chalkiness of rice grain, and had no significant impact on the starch content of rice grain but tended to reduce the amylose content and increase the ratio of amylopectin to amylose. And the highest values of the amylose content and the ratio of amylopectin to amylose existed in the NW and AW plots which were 4.5% lower and 4.6% higher than those in the control plots in 2008, respectively. The activity of ADPG-PPase in grain decreased under the warmed plots during the early phase of rice grain filling,while had certain differences during the middle and late phases of rice grain filling. Warming treatments had no significant effect on the activity of SBE in grain. There were increasing trends of peak viscosity, hot viscosity, break down and pasting temperature, and decreasing trends of final viscosity, setback and consistency in rice grain under the warmed plots. The highest increase of peak viscosity and break down existed in the AW plots, and the highest decrease of final viscosity and consistency existed in the DW plots compared with those in control plots. The content of grain protein was decreased by warming treatments. Grain protein contents were significantly decreased by 5.6% and 4.0%, respectively in the AW and NW treatments. The activities of GS and GOGAT in grain were decreased under the warmed plots during the early phase of rice grain filling, while there were differences for them during the middle and late phase of rice grain filling. All these results suggest that milling and appearance qualities of rice would get worse under warming plots. The impact of ADPG-PPase activity was greater on amylose content and that of SBE on amylopectin content in rice during the early phase of grain filling. The protein synthesis was closely related to the activities of GS and GOGAT during the early phase of rice filling. Therefore, the effects of asymmetric climate warming on grain quality and activities of key enzymes for single cropping rice are complicated.

Effects of Nitrogen Management on Protein Expression of Flag Leaves during Grain-Filling Period in Large Panicle Rice (Oryza sativa L.)

ZHANG Zhi-Xin, LI Zhong, CHEN Jun, LI Ai-Song, CHEN Long-Fu, CHEN Hong-Fei, HUANG Jin-Wen, LIN Wen-Xiong

Acta Agron Sin. 2011, 37(05):  842-854.  doi:10.3724/SP.J.1006.2011.00842

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In rice (Oryza sativa), approximately 60%–100% of the carbon in mature grains originates from CO₂ assimilation during the grain-filling period, with the flag leaf as the most important contributor to the yield. It is therefore important to understand molecular mechanisms of flag leaf during the grain-filing period. Two-dimensional electrophoresis (2-DE) technology was applied to investigate the differential expression patterns of leaf proteins from different periods during grain-filling process in rice cultivation Jinhui 809 treated by two different nitrogen application ratios. The results showed 32 differentially expressed proteins with 27 up-regulated and five down-regulated, in response to increased nitrogen application at grain-filling stage. According to their relative functions the identified proteins were classified into five main categories: photosynthesis (12); adversity-resistance response (5); hormone synthesis and signal transduction (5); cell growth and differentiation (5); unknown functions (5). Then photosynthesis-related features together with adversity-defense related indicators (SOD, POD, CAT, MDA, and soluble protein) were determined. The appropriate increase in nitrogen application at late growth stage on one hand delayed the degradation of chlorophyll and soluble protein in leaf during grain filling period, in turn elongated the leaf photosynthesis process; on the other hand promoted the activities of SOD, POD, CAT, while decreased the lipid peroxidation degree, which together indicated the strengthen of leaf adversity-defense ability. The results not only verify the high efficient effect of increased nitrogen application on leaf metabolisms during grain-filling process, but also provide the theoretic basis for studies on rational management of nitrogen fertilizer and its relevant molecular regulation in the future.

Effects of “San-Ding” Cultivation Method on Yield Formation and Physiological Characteristics of Double Cropping Super Rice

JIANG Feng, HUANG Min, Md.Ibrahim , CENG Yan, JIA Bing, JU Ying-Bin

Acta Agron Sin. 2011, 37(05):  855-867.  doi:10.3724/SP.J.1006.2011.00855

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Rice is the major staple food of China. The realization of its high yield has a great significance for food security and society stability. A field experiment was conducted in Changsha and Liuyang cities of Hunan Province during 2008–2010 to find out a cultivation technique that could increase the yield of double cropping super rice in South China. Super early rice Luliangyou996 and Lingliangyou 268 and super late rice Tianyouhuazhan and Fengyuanyou 299 were used in early and late season cropping, respectively. The cultivation patterns were designed as “Sanding” cultivation (tillage and transplanting, A), no tillage and seedling broadcasting (B), traditional cultivation (C) and no applied fertilizer (D). The characteristics of grain yield formation and their physiological attributes under different cultivation patterns were analyzed. Result showed that the grain yield of pattern A was significantly higher among the tested patterns irrespective of growing seasons, locations and years. Compared with pattern C, the pattern A significantly increased root bleeding intensity per flowering glume, root oxidation ability,root-shoot ratio, LAI and photosynthetic rate in flag leaves at heading stage, and the SPAD reading of pattern A decrease slowly and dry matter production was higher from heading to maturity stages. The average grain yield of pattern A (7.18 t hm^-2 and 8.39 t hm^-2 in early and late season rice, respectively) was 11.68% and 7.41% higher in early and late season, respectively, mainly due to the contribution of higher number of productive tiller and grain number per panicle. The dry matter accumulation and number of productive tiller of pattern B was higher but the harvest index (HI) and grain-filling percentage were lower than those of pattern C and there was no significant yield increasing or decreasing trend. Thus, the physiological characteristics could be improved through the practicing of “Sanding” cultivation technique which is very important to increase grain yield especially in South China rice production.

Simulation of Canopy Photosynthetic Production Based on Plant Type in Rice

LI Yan-Da, ZHU Xiang-Cheng, TANG Liang, CAO Wei-Xing, ZHU Yan

Acta Agron Sin. 2011, 37(05):  868-875.  doi:10.3724/SP.J.1006.2011.00868

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By using canopy-light-distribution-based photosynthetic model, and designing various combinations of model input parameters for compact and loose plant types of rice, quantitative analyses were made on the diurnal variation in extinction coefficient of canopy direct radiation with different plant types, the vertical distribution characteristics of direct radiation at noon and of photosynthetic rate within canopy, the characteristics of canopy photosynthetic rate with the changed leaf area index (LAI) under different radiant intensities, as well as the diurnal variation of canopy photosynthetic rate under different radiant intensities. The results showed that the high yield potential of compact plant type in rice relied on higher LAI, leaf photosynthetic efficiency, solar altitude and the intensity of solar radiation. These results would provide a support on cultivation for high yield and optimal design of plant type in rice crop.

Response of Gas Exchange, Chlorophyll a Fluorescence and Anti-oxidation Enzymes Activities to Osmotic Stress in an Upland Rice Progeny YF2-1 Derived from Oryza sativa × Echinochloa caudata

DING Zai-Song, WANG Chun-Yan, GUAN Dong-Meng, DIAO Feng-Wu, DIAO Meng

Acta Agron Sin. 2011, 37(05):  876-881.  doi:10.3724/SP.J.1006.2011.00876

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Wild species generally have higher stress resistance than cultivated crops and are utilized as the sources of stress resistance genes in stress resistance improvement of crops. In rice, its wild relatives have been used to improve photosynthesis, yield and stress resistance. YF2-1 is obtained by distant cross between Oryza sativa and Echinochloa caudate. In order to assess its osmotic stress resistance on physiological level, gas exchange, chlorophyll a fluorescence and antioxidation enzyme activities under osmotic stress simulated by PEG-6000 were studied in seedlings of upland rice YF2-1 and H65.The results showed that YF2-1 maintained higher net photosynthetic rate and stomatal conductance under osmotic stress condition, indicating YF2-1 suffered less inhibition in photosynthesis. This may be related to its higher water retaining capacity and its effective functions for high excessive light energy dispersing (higher NPQ) and higher activities of anti-oxidation enzymes SOD, POD, and CAT, effectively clearing AOS produced by excessive light energy. The result shows that the distant crossing may increase the resistance to osmotic stress in rice.

Characteristics of Nutrient Uptake and Utilization of Mid-Season Hybrid Rice under Different Nitrogen Application Rates in Different Locations of Southwest China

XU Fu-Xian, XIONG Hong, ZHANG Lin, GUO Xiao-Yi, SHU Yong-Chuan, ZHOU Xin-Bing, LIU Mao

Acta Agron Sin. 2011, 37(05):  882-894.  doi:10.3724/SP.J.1006.2011.00882

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The characteristics of nitrogen (N), phosphorus (P) and potassium (K) uptake and their utilization of mid-season hybrid rice were studied. Field experiment were conducted with mid-season rice combinations II-you 7 and Yuxiangyou 203 grown under the condition of different ecological sites, chemical qualities of soil and the levels of N application in 2009. By using variance, correlation, regression and partial correlation analysis, the results indicated that significant or highly significant differences of grain yield, dry matter production, uptake amount and harvest indexes of N, P, K and N, P, K requirements of above ground plants for producing of 1 000 kg grains (RAGPPG) were found among seven locations. There were significant or highly significant effects of fertilizer application treatments on grain yield, dry matter production, uptake amount, harvest index and N among RAGPPG, but no effect on P and K among RAGPPG. Highly significantly positive correlations were observed among harvest indexes of N, P, K and among RAGPPG, but not between harvest indexes of N, P, K; RAGPPG and grain yield. Multiple stepwise regression analysis showed that harvest indexes of N, P, K and RAGPPG were significantly influenced by different ecological sites, chemical qualities of soil and the levels of N application, and the determination coefficients ranged from 0.5972–0.8404 and 0.7637–0.8804。The results provide a scientific basis for the determination of the efficient amount of N, P, and K applied for full scale rice cultivation.

A Simulated Study on the Effects of Seasonal Drought on Growth and Yield of Double Cropping Rice in Hunan Province

FENG Li-Ping, MO Zhi-Hong, HUANG Wan-Hua, YANG Xiao-Guang, PAN Hua-Biao

Acta Agron Sin. 2011, 37(05):  895-902.  doi:10.3724/SP.J.1006.2011.00895

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Seasonal drought is one of the most serious disasters in rice production in Hunan province of China. On the basis of calibration and validation of rice model ORYZA2000, the characteristics of seasonal drought and its effect on growth and yield of double cropping rice under three types of water management with continued flooding (CF), alternative wet and dry (AWD), and rainfed (RF) conditions were simulated and analyzed with history weather data from 1960 to 2007. The results was as follows, (1) The soil seasonal drought of double rice gradually occurred from panicle initiation (PI) under AWD and RF conditions, and got more serious in the process of growth, especially under rainfed condition. The late rice tended to be more easily affected by seasonal drought than early rice, and the seasonal drought was more serious at late stage than early stage. The effect of drought on biomass and yield of rice was the severest at flowering stage. The characteristics between soil drought and crop drought showed differently. (2) There appeared seasonal drought for both early and late rice under the year types of normal and dry. The drought was serious for early rice from early PI to maturity under dry year type, and its strength and duration surpassed that of normal year type. The frequency and strength of drought for late rice excessed that of early rice under dry year type, especially from PI to maturity. (3) The seasonal drought caused different losses of yield in double rice. Higher yield of rice occurred under AWD, while the lowest yield occurred under RF. The yield of late rice was lower than that of early rice under rainfed condition. This quantitative study could provide a theoretical basis for the disaster mitigation of seasonal drought and sustainable water management in double rice production in Hunan.

Changes of Matter Accumulation and Relative Enzymatic Activity during Yam Tuber Development

LIANG Lin-Fan, LI Chuang-Zhen, ZHANG Juan, HE Long-Fei, HUI Ben-Hui, GAN Xiu-Qin, HE Hu-Yi

Acta Agron Sin. 2011, 37(05):  903-910.  doi:10.3724/SP.J.1006.2011.00903

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Tuber development is a complex physiological process, involving in changes of various components and enzymes activities, so learning about changes of the matter accumulation and enzymes metabolism will help to instruct yam production. In the paper, two different cultivars Guihuai 5 and Guihuai 16 were used to investigate some physiological and biochemical indicators during yam tuber development in 2009—2010. The results showed that tuber length and dry matter content were kept increasing, but AMYenzyme activity decreasingduring the tuber development. The main carbohydrates contents, functional substances, and the activities of POD, AI, and SPS presented similar trend: continually increased firstly, and reached various peaks, then decreased. The changes of reducing sugar content and AGPase activity were different between two cultivars. The t-test results indicated that there was a significant difference between two cultivars in dry matter (P=0.011),starch (P=0.031), and saponin (P=0.019). Sucrose content was significantly correlated with soluble sugars content (r₅=0.97^**, r₁₆=1.00^**), AGPase activity (r₅= –0.85^*) and reducing sugars content (r₁₆=0.87^*), and starch content was significantly correlated with polysaccharides (r₅=0.95^**), Vc (r₅=0.83^*) and saponin (r₁₆=0.88^**) contents as well as tuber length was significantly correlated with dry matter content (r₅=0.97^**, r₁₆=87^*), AMY activity (r₁₆= –0.95^**),AGPase activity (r₁₆= –0.90^**) andprotein content (r₁₆=0.83^*). To sum up, the sucrose accumulation, SPS and AIactivity play a key regulatory effect in yam tuber development,the main functional substances are close correlated between each other.

Effect of Soil Water Deficit and High Temperature on Leaf Cuticular Waxes and Physiological Indices in Alfalfa (Medicago sativa) Leaf

GUO Yan-Jun, NI Yu, GUO Yun-Jiang, HAN Long, TANG Hua, YU Yong-Xiong

Acta Agron Sin. 2011, 37(05):  911-917.  doi:10.3724/SP.J.1006.2011.00911

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Cuticular wax, exposed at the outermost surface of plant organs, plays important roles in interactions of plant with environment and plays a critical role in plant drought tolerance by reducing cuticular water loss. In the experiment, two alfalfa (Medicago sativa) cultivars with different drought resistances, Aohan (high resistance) and Sanditi (low resistance), were selected to analyse the dynamics of leaf cuticular wax content and components, and the relationships between waxes and gas exchange indices under water deficit and high temperature stresses. The results showed that the alfalfa leaf surface was covered by thick wax platelets without specific orientations, which were constituted of alkanes (1.98%–3.38%), primary alcohols (79.97%–84.98%), esters (0.08%–0.24%), and small amount of unknown constituents (7.77%–13.38%). The wax deposition on alfalfa leaf was controlled by both variety type and environments. The wax content of Aohan was significantly higher than that of Sanditi. Under drought treatment, the proportions of alkanes in total wax increased (81.22%–108.16%), that of primary alcohol decreased (3.23%–12.54%); cuticular wax, photosynthetic rate (P_n), transpiration rate (T_r), and stomatal conductance (G_s) of Aohan changed insignificantly except for intercellular carbon dioxide (C_i), while those of Sanditi decreased significantly, indicating that cuticular wax might take part in the process of water metabolism and the alkanes in total waxes might play important role in controlling water loss. Under the conditions of high temperature, P_n, T_r, G_s, C_i, and leaf relative water content decreased significantly, water use efficiency (P_n/T_r) and proline content increased significantly in both cultivars; the total cuticular wax content unchanged in Aohan but significantly decreased in Sanditi, indicating that stomatal closure and osmotic adjustment were the main paths taken by alfalfa under severe stressed conditions.

RESEARCH NOTES

Expression Analysis of Three Genes from SSH Library Constructed Using Tillering Nodes of Dongnongdongmai 1 under Low Temperature

MAO Yong-Chao, CUI Gong, XU Jing, CENG Yan, MENG Jian-Nan, CANG Jing

Acta Agron Sin. 2011, 37(05):  918-923.  doi:10.3724/SP.J.1006.2011.00918

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To reveal the molecular mechanism of cold resistance of winter wheat variety Dongnongdongmai 1, under natural conditions in the north region of China, we collected tillering nodes before (5°C) and in winter season (-25°C) respectively, then constructed cDNA library of Dongnongdongmai 1 containing low temperature stress related genes by suppression subtractive hybridization. A total of 300 positive clones selected from cDNA library randomly were sequenced to obtain 230 high quality expressed sequence tags (EST). After BLAST and functional annotation, we found complex and diverse types of genes in the library, including stress response genes (such as heat shock protein, CS66, Wcor8 and other related genes) and genes encoding 40S and 60S ribosomal subunit. These genes with high frequency may play an important role in protecting Dongnongdongmai 1 from injuring under low temperature. Two unknown genes and Clp selected from the cDNA library were analyzed through quantitative PCR. The expression levels of these genes in Dongnongdongmai 1 were increased in various degrees with the decrease of temperature; however, their expression patterns were different in Jimai 22 (a winter wheat cultivar with low resistance to low temperature). This result suggests that these genes may play an important role in resistance to low temperature stress.

Allelic Variations of Phytoene Synthase Genes Controlling Yellow Pigment Content in Durum Wheat (Triticum turgidum L.)

GUO Hui-Juan, CHEN Feng, DONG Zhong-Dong, CUI Dang-Qun

Acta Agron Sin. 2011, 37(05):  924-929.  doi:10.3724/SP.J.1006.2011.00924

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A total of 177 durum wheat (Triticum turgidum L.) cultivars from five countries or regions were used to identify allelic variations of phytoene synthase (PSY) genes located on chromosomes 7A and 7B using allele-specific markers of YP7A-2, YP7B-1, YP7B-2, YP7B-3, and YP7B-4. Two alleles, previously designated as Psy-A1d and Psy-A1e, were identified on chromosome 7A (Psy-A1). The distribution percentages of the two alleles were 76.8% and 23.2%, respectively. Furthermore, six allelic variants, previously designated as Psy-B1b, Psy-B1c, Psy-B1d, Psy-B1e, Psy-B1f, and Psy-B1g, were identified on chromosome 7B (Psy-B1) with distribution percentages of 9.0%, 0.6%, 0.6%, 6.9%, 25.4%, and 57.6%, respectively. Interestingly, three allelic variants of Psy-B1b, Psy-B1c, and Psy-B1d were never reported in durum wheat before. This result enriched the polymorphism of Psy1 gene in durum wheat. On Psy7A and Psy7B loci, 34, 12, and 1 cultivars were found to possess allelic combinations of Psy-A1d/Psy-B1f, Psy-A1d/Psy-B1e, and Psy-A1d/Psy-B1c, respectively, which were genotypes of high yellow pigment content. Other 28 and 1 cultivar, with Psy7A and Psy7B combinations of Psy-A1e/Psy-B1g and Psy-A1e/Psy-B1b, respectively, were associated with low content of yellow pigment. These results may help material selection in durum wheat breeding aiming at quality improvement.

Effects of Cadmium Stress on the Seed Quality Traits of Transgenic Cotton SGK3 and ZD-90

LI Ling, CHEN Jin-Gong, CHU Shui-Jin

Acta Agron Sin. 2011, 37(05):  929-933.  doi:10.3724/SP.J.1006.2011.00929

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A pot experiment was conducted to study the physical and nutritional quality traits of seeds in transgenic cotton SGK3 and ZD-90 under cadmium (Cd) stress, using TM-1 as the check. The results showed that the Cd content in the kernels of the three experimented cotton materials increased linearly with the increase of cadmium level treated. Among the materials used in the experiment, the Cd content in the kernels of SGK3 was higher significantly than those of others, which indicated that SGK3 was an outstanding cotton germplasm for accumulation of cadmium. In addition, Cd stress could reduce the physical and nutrient quality traits of cottonseeds significantly. According to the results of experiment, the resistance to Cd stress for the materials used in this experiment was in the order as: SGK3>ZD-90>TM-1.