Table of Content

12 October 2010, Volume 36 Issue 10

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Association Analysis between Submergence Tolerance and SSR Markers in Domestic and Foreign Soybean Cultivars in Asia

SUN Hui-Min,ZHANG Jun,ZHAO Tuan-Ji,GAI Jun-Yi

Acta Agron Sin. 2010, 36(10):  1615-1623.  doi:10.3724/SP.J.1006.2010.01615

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Association mapping is one of the important ways to detect QTLs and reveal genetic bases of target traits in the natural populations. According to the analyses of genetic structure of the total 291 Asian soybean accessions with 64 simple-sequence repeat (SSR) markers, the tested population was divided into Chinese population (Population 1) and exotic population (Population 2). Linkage disequilibrium was detected extensively in both populations. The results of association mapping showed that total 3, 7, and 12 SSR loci in Population 1 were associated with three submergence tolerance traits, i.e. relative seedling death rate, relative chlorophyll deficiency rate and relative wilting rate, while 6, 3, and 5 associated SSR loci were in Population 2. Several loci were associated simultaneously with two or three tolerance traits, indicating their common genetic bases, while some loci were consistent with QTLs detected from family-based linkageship mapping procedure. Total 24 and 22 elite alleles of the three indicators of submergence tolerance, as well as their carriers, were detected in the two populations, respectively. The frequency distribution of elite allele of relative seedling death rate varied among five major pedigrees of released cultivars from Huang-Huai-Hai Valleys and southern China. Some cultivars, such as Hedou 2 Hao, Qiandou 3 Hao, Youbian 31, and Nannong 493-1 in Population 1, and PI208432, PI377576, PI481690 in Population 2, with elite alleles and performance of tolerance to submergence were selected as donors in breeding for tolerance to submergence stress in soybean.

Correlation Analysis and Conditional QTL Analysis of Grain Yield and Yield Components in Maize

PENG Bo, WANG Yang, LI Yong-Xiang, LIU Cheng, ZHANG Yan, LIU Zhi-Zhai, TAN Wei-Wei, WANG Di, SUN Bao-Cheng, DAN Yun-Su, SONG Yan-Chun, WANG Tian-Yu, LI Yu

Acta Agron Sin. 2010, 36(10):  1624-1633.  doi:10.3724/SP.J.1006.2010.01624

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Grain yield per plant (GYPP) is one of the most complicated quantitative traits and determined by kernel number per plant (KNPP) and 100-kernel weight (KWEI) in maize. It is of great importance in genetic improvement to reveal genetic relationship between GYPP and two yield components (KNPP and KWEI). In the present study, an F_2:3 population including 230 families derived from two foundation lines in maize breeding of China (Qi 319 and Huangzaosi) was used to conduct conditional analysis and QTL mapping. The genetic relationships between GYPP and yield components (KNPP and KWEI) were investigated. The results showed that the heritability of KWEI was higher than that of GYPP and KNPP, and KWEI was less influenced by environment. The phenotypic correlation analysis showed that both KNPP and KWEI were positively significantly correlated with GYPP, and the correlation coefficient between KNPP and GYPP was higher than that between KWEI and GYPP. A total of five QTLs and five pairs of epistatic loci were detected for GYPP by the unconditional QTL mapping. Among the five QTLs, four were found with pleiotropic effects on three traits (GYPP, KNPP, and KWEI), while another one controlled two traits (GYPP and KNPP). All of the five pairs of epistatic loci were related to both KNPP and KWEI. Furthermore, fourteen QTLs and ten pairs of epistatic loci with small effects were detected only in the conditional QTL mapping. Consequently, either KNPP or KWEI was closely related with GYPP at phenotypic level, suggesting that the improvement of KNPP and KWEI can efficiently contribute to high grain yield. The conditional QTL mapping demonstrated the strong genetic relationship between GYPP and two yield components (KNPP and KWEI) at the individual QTL level. The conditional QTL mapping could detect additional QTLs with small effects that were not detected in the unconditional QTL mapping. Two important QTLs with pleiotropic and larger effects could be used in maize breeding for high yield and fine mapping.

Cloning and SNP Analysis of TT1 Gene in Brassica juncea

YAN Ming-Li,LIU Xian-Jun,GUAN Chun-Yun,LIU Li-Li,LU Ying,LIU Zhong-Song

Acta Agron Sin. 2010, 36(10):  1634-1641.  doi:10.3724/SP.J.1006.2010.01634

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The quality of rapeseed can be further improved through the development of yellow-seeded cultivars, which are known to contain less lignin and more proteins, both enhancing the dietary feed value. The TT1 gene encodes a WIP domain protein with Zn-finger, which is essential for seed coat development and organ color in Arabidopsis, its mutation causes transparent testa. In order to study molecular mechanism of seed coat color in rapeseed, TT1 gene was cloned from Brassica juncea using homology-based cloning and RACE (rapid-amplification of cDNA ends) strategy. A modified allele-specific PCR procedure developed for assaying single nucleotide polymorphisms of TT1 gene in Brassica juncea. In this study, cloning and characterization of the orthologous TT1 gene from Brassica juncea were reported. The full length DNA sequence of TT1 gene was 2 197 bp with one intron. The TT1 cDNA sequence was 1 412 bp in length, 903 bp of which was open reading frames (ORF) encoding a deduced polypeptide of 300 amino acids with a predicted molecular weight of 33.97 kD and an isoelectric point of 6.99. The above-mentioned genomic sequences showed 99% identity with the TT1 gene from Brassica napus, and 85% identity with the TT1 gene from Arabidopsis. RT-PCR analysis showed that TT1 expressed in the seed coats of both the black- and the yellow-seeded B. juncea lines. Comparison of sequences of Sichuan Yellow (yellow seed) and purple-leaf mustard (black seed) revealed nucleotide variation at the eight sites which all are located within the coding region of the gene. However, the mutations of the TT1 gene at these sites had no effect on the seed coat color in B. juncea through comparing the sequences of NILB and purple-leaf mustard. The allele-specific PCR of the TT1 gene could distinguish purple-leaf mustard from Sichuan Yellow.

DNA Fingerprinting Analysis of 18 Cassava Varieties Using Sequence-Related Amplified Polymorphism Markers

JI Lan,WANG Wen-Quan,ZHANG Zhen-Wen,YE Jian-Qiu,LI Kai-Mian

Acta Agron Sin. 2010, 36(10):  1642-1648.  doi:10.3724/SP.J.1006.2010.01642

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There widely exists a case of same name for more varieties or different names for one variety in cassava agriculture production, so it is difficult to identifycassava varieties on the basis of the phenotypic characters. In the paper, SRAP marker was applied to detect 18 cassava varieties, thirty-six primer combinations were selected with abundant polymorphism, a total of 320 bands were scored, 235 (73.4%) out of them were polymorphic, with an average of 8.9 bands and 6.5 polymorphic bands for each primer combination, 235 polymorphic bands then were used to develop a dendrogram with Unweighted Pair-Group Method Arithmetic Average (UPGMA), and 18 cassava varieties were divided into four major groups at the 0.734 similarity level; two primer combinations Me1-Em5 and Me24-Em10, were used to develop the DNA fingerprints for the 18 cassava varieties. The DNA fingerprints were then converted into binary codes, with 1 and 0 representing band presence and absence, respectively. In the DNA fingerprints, each of the 18 cassava varieties had its unique binary code, which distinguished varieties between each other easily, with 99.999% probability of confidence. The results demonstrated that it is feasible to distinguish varieties with DNA fingerprints established by SRAP.

Identification of Molecular Markers Associated with Seed Dormancy in Mini Core Collections of Chinese Wheat and Landraces

ZHANG Hai-Ping,CHANG Cheng,YU Guang-Xia,ZHANG Xiu-Ying,YAN Chang-Sheng,XIAO Shi-He,SI Hong-Qi,LU Jie,MA Chuan-Xi

Acta Agron Sin. 2010, 36(10):  1649-1656.  doi:10.3724/SP.J.1006.2010.01649

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Seed dormancy evaluated by germination index (GI) is often regarded as a main and pivotal component of observed genetic variation for pre-harvest sprouting (PHS). Improving seed dormancy can decrease or avoid PHS damage to wheat (Triticum aestivum L.) before harvest, but it is a complicated trait controlled by multi-genes and influenced by many environmental factors. Because seed dormancy is difficult to be accurately evaluated under field condition, molecular markers will play an important role in dormancy evaluation. In this study, four SSR markers (Xbarc57, Xbarc294, Xbarc310, and Xbarc321) on the short arm of chromosome 3A and a gene-based marker (Vp1-b2) derived from Vp-1B on 3BL were used for genotyping 138 mini core collections of Chinese wheat and landraces. The results indicated that rich alleles occurred in the five markers, and most were significantly correlated with GI value. Based on general linear model, the five markers were significantly associated with seed dormancy. Markers Vp1-b2 and Xbarc294 had stronger effects on seed dormancy than other markers, accounting for 65.8% and 61.2% of seed dormancy variation, respectively. Marker combination could promote the percentage of phenotypic variation explained, of which the combination of five markers estimated 95.9% of the GI variation, followed by the combination of Vp1-b2 and Xbarc294 (89.1%), and the combination of Vp1-b2 and Xbarc321 had the smallest estimation of GI variation (79.4%). These results indicate that seed dormancy is mainly attributed to loci Vp1-b2 and Xbarc294 on 3AS and 3BL in the 138 genotypes, and the evaluation accuracy can be enhanced by jointly application of the total five markers in markers-assisted selection.

Genetic Dissection of Segregation Distortion in Interspecific BC₁ Populations of Cotton

YU Yu,ZHANG Yan-Xin,LIN Zhong-Xu,ZHANG Xian-Long

Acta Agron Sin. 2010, 36(10):  1657-1665.  doi:10.3724/SP.J.1006.2010.01657

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Segregation distortion (SD) is the deviation of genetic segregation ratios from their expected Mendelian fashion and is a common phenomenon found in most genetic mapping studies. In our previously genetic map published, 107 SSR markers showed SDin the BC₁ mapping population [(Emian 22×3-79) × Emian 22]. To verify their segregation in other populations and to clarify the possible mechanism of SD, 97 co-dominant markers of them were evaluated in another two backcross populations. The results showed that 61 distorted markers in the mapping population segregated normally in the other backcross populations, which implied that the cross way is a major factor affecting segregation distortion. Thirty-six markers showed segregation distortion in at least two populations, which is assumed to be caused by gametic selection. These distorted markers distributed on 14 Chromosomes with more markers in D sub-genome than in A sub-genome. Chr.2, Chr.16, and Chr.18 were the Chromosomes with more distorted markers than others, which implies that there must be segregation distortion loci on these Chromosomes, leading us to identify segregation distortion loci in cotton.

Cloning and Tolerance Analysis of GsANN Gene Related to Response on Stress in Glycine soja

WANG Xi, LI Yong, ZHU Yan-Ming, BAI Xi, CAI Hua, JI Wei

Acta Agron Sin. 2010, 36(10):  1666-1673.  doi:10.3724/SP.J.1006.2010.01666

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Abiotic stresses, such as salt and drought, affect plant growth, development and reduce crop yield. Glycine soja is an excellent material to clone abiotic stresses related genes because of its high stress tolerance. In previous work, an EST database was constructed using a salt-tolerant variety of G. soja, and a gene expression profile was also obtained by microarray hybridization. Expression of all G. soja ESTs was analyzed, and one 3¢-EST was found to be induced by stress, representing an annexin (ANN) gene, a widely-existing super family which has been found to respond to some kinds of abiotic stresses and plays roles in many important cellular processes including membrane formation, regulation of ion channels, signal transduction and so on. Complete coding sequence of this annexin gene was obtaind with developed 5¢-RACE and named as GsANN. Translation product of GsANN had 57% similarity with ANN4 of Arabidopsis thaliana. GsANN had three ANN domains, with moderate hydrophobicity/hydrophilicity, and no signal peptide or transmembrane segment, which was consistent with other ANNs of other plants. Localization of GsANN protein was analyzed by transient expression in tobacco epidermis cells and the result showed that GsANN localized around plasma membrane unevenly and might form oligomers. Semi-quantitative RT-PCR showed the expression level of GsANN was induced by drought and salt stresses in G. soja leaf. Arabidopsis thaliana plants overexpressing GsANN showed lower survival rate and higher sensitivity under both salt and drought stresses. GsANN is a novel ANN gene and is closely related to salt and drought stresses, so it can either be used as a new resource in gene engineering on stress tolerance or be further studied to provide more information for the researches on the mechanism of stress tolerance of plant.

Mapping Quantitative Trait Loci for 100-Seed Weight in Soybean (Glycine max L. Merr.)

WANG Xia, XU Yu, LI Guang-Jun, LI He-Na, GEN Wen-Quan, ZHANG Yuan-Ming

Acta Agron Sin. 2010, 36(10):  1674-1682.  doi:10.3724/SP.J.1006.2010.01674

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100-seed weight is an important yield component of soybean and has been positively correlated with seed yield. A genetic linkage map using 504 F₂ plants from direct and reciprocal crosses between Lishuizhongzihuang and Nannong 493-1 was constructed. 100-seed weight for these F_2:4 families were measured at Jiangpu experimental station of Nanjing Agricultural University and Linyi experimental station in 2008, respectively. The above information was used to detect quantitative trait locus (QTL) for 100-seed weight using composite interval mapping (CIM) in Win QTL Cartographer V. 2.5 and joint analysis under the framework of penalized maximum likelihood. The results showed that sixteen QTLs were identified by the CIM while thirty-nine QTLs, including twenty-four main-effect QTLs, one environmental effect, one cytoplasmic effect, one environmental interaction and twelve cytoplasmic interactions, were detected by joint analysis. Ten common main-effect QTLs detected by the above two methods, three common QTLs between direct and reciprocal crosses at the two environments, and four consensus QTLs from Meta analysis showed the stability of the results. These results provide a theoretical basis for genetic analysis of soybean yield and marker-assisted breeding.

Cloning and Expression Analysis of TaG3BP Gene Related to Fertility Conversion in Male Sterile Lines of Wheat

ZHOU Lin-Lin, SONG Guo-Qi, LI Hong-Yan, HU Yin-Gang, HE Pei-Ru

Acta Agron Sin. 2010, 36(10):  1683-1690.  doi:10.3724/SP.J.1006.2010.01683

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Thermo-photoperiod sensitive male sterile (TMS) wheat (Triticum astivum L.) is a valuable material for heterosis study and utilization by means of two-line system. YS-type TMS lines are applicable in hybrid wheat in major wheat growing areas in northern China. The objective of this study was to reveal the molecular basis of fertility conversion in YS-type TMS wheat. YS-type TMS line A3017 was grown in a phytotron with controlled temperatures in favor of male sterility and fertility, respectively. Two suppression subtractive hybridization (SSH) cDNA libraries were constructed using cDNA from the male sterile and fertile young spikes of the same individuals that were orderly treated with temperature cycle (day/night) of 16℃/12℃ and 25℃/16℃. Using a pair of primers designed on the basis of aligned homological sequence, RT-PCR amplification was carried out and an EST with 1230 bp in length (GenBank accession number: DY543200) was obtained from the fertile SSH-cDNA library, which encodes 409 amino acid residues. The cDNA fragment contained the typical NTF2 and RRM domains of G3BP, and designated TaG3BP (GenBank accession number: GU475149). The deduced amino acids had 79% of similarity with G3BP (Ras-GTPase activating protein SH3 domain-binding protein) gene from Oryza sativa (BAD07751). The expression pattern of TaG3BP was analyzed with Real-time PCR using anthers from the TMS line in various developmental periods under male sterile and fertile conditions. In fertile anthers, TaG3BP gene was expressed in a higher level at the critical stage of fertility conversion (between uninucleate and binucleate stages) as compared with those in sterile anthers. In the K-type male-sterile lines and their maintainers of 1B/1R, 1B and non 1B/1R types, TaG3BP gene showed higher expression levels in the young spike of maintainers than in that of the male-sterile lines. These results suggest that the expression of TaG3BP gene is related to fertility conversion in male-sterile wheat lines.

Establishment of Agrobacterium tumefaciens -mediated Anther Calli Transformation System in Hevea brasiliensis

HUANG Tian-Dai, LI Zhe, SUN Ai-Hua, ZHOU Quan-Nan, HUA Yu-Wei, HUANG Hua-Sun

Acta Agron Sin. 2010, 36(10):  1691-1697.  doi:10.3724/SP.J.1006.2010.01691

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Developping a new Hevea variety by crossing breeding will take 20-30 years, but genetic transformation provides an effective alternative for shortening breeding cycle. Until now, two kinds of recipient materials, anther compact embryogenic calli (ACEC) and maintained friable embryogenic calli (MFEC), have been used successfully for Hevea genetic transformation. However, few transformed plants are produced from ACEC-derived embyos, and plants regenerated from MFEC are abnormal, showing that they have poorer performance in growth, yield and disease resistance than the budded control. In order to establish Agrobacterium tumefaciens-mediated Hevea factors influencing transformation frequency, including strains of Agrobacteriumembryos regeneration. GUS transient expression frequency was significantly affected by Agrobacterium strains and co-culture temperature/time, which was 5.07 blue spots/callus for EHA105, higher than that for GV3101 and LBA4404. The highest GUS transient expression frequency was 8.43 and 19.10 blue spots/callus under 22℃ co-cultured temperature and 6 days co-cultured time respectively. Twenty-two thousand ACEC were transformed by the strain EHA105 with pCAMBIA2301, and then transferred to the medium without AS and incubated at 22℃ for 6 days in the dark. Subsequently, 11 transformants were identified by GUS staining, PCR amplification of target genes, sequencing of PCR products and Southern hybridization. Among them, three planted directly in the field died; three as scions were budded onto seedlings, producing five budded transgenic plants; five were multiplicated at embryo phase by secondary embryogenesis, producing 676 transgenic plantlets, among which 248 survived in the field. The results showed that the present transformation system and the plant propagation by transgenic embryos secondary embryogenesis are efficient for the production of transgenic rubber plants., co-culture temperature/time and acetosyringone (AS), and the methods for anther calli transformation system, we surveyed the

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of N, P, and K Fertilizer Application on Cotton Grown in Saline Soil in the Yellow River Delta

XIN Cheng-Song, DONG He-Zhong, LUO Zhen, TANG Wei, ZHANG Dong-Mei, LI Wei-Jiang, KONG Xiang-Qiang

Acta Agron Sin. 2010, 36(10):  1698-1706.  doi:10.3724/SP.J.1006.2010.01698

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It is urgent and necessary to provide the technology of economic application on fertilizers for nutrition improvement of Bt cotton and cotton production in coastal saline soil in the Yellow River Delta. The experiments were conducted with Bt cotton cultivar SCRC28 in coastal saline soil in the Yellow River Delta, Shandong province. The effects of different amounts and ratios of N, P and K, and N and P fertilizers on nutrient (N, P and K) assimilation, Na⁺ assimilation, net photosynthetic rate (P_n), dry matter accumulation and lint yield of Bt cotton were investigated in three types (low, middle and high levels of salinity) of coastal saline field. The results showed that nutrient uptake of Bt cotton in the treatments of NP, NPK especially, in low, middle and high levels of salinity field was significantly higher than that in corresponding controls. And the Na⁺ uptake of cotton in the same treatments was significantly lower than that in corresponding controls. Nutrient use efficiency in agronomy(NUEa) of cotton in the NPK treatment in low, middle and high levels of salinity field was the highest among the three treatments. NUEa of Bt cotton in the NPK treatment in low, middle and high levels of salinity field was 0.20, 1.95, and 2.07 kg lint kg^–1 N, 0.87, 8.35, and 8.71 kg lint kg^–1 P, and 0.26, 2.89, and 3.77 kg lint kg^–1 K, respectively. The coordination of N, P and K fertilizers could maintain the highest leaf area, chlorophyll content and P_n among the three treatments in low, middle and high levels of salinity field, respectively. The biomass yield and lint yield of Bt cotton in the NPK treatment in low, middle and high levels of salinity field were also the highest among the three treatments, respectively. The lint yield in the NPK treatments in low, middle and high levels of salinity field was 2.53%, 28.67% and 30.47% higher, respectively, than that in corresponding controls. And the fertilization effects in middle and high levels of salinity field were obviously better than those in low level of salinity field. Further analysis indicated, rational fertilizer application, according to the classification of soil salinity, was an effective way to alleviate nutrition obstacles of saline soil, improve cotton nutrition, and enhance the NUEa and cotton yield in coastal saline fields.

Effects of Sowing Date on Accumulation and Distribution of Biomass and Nitrogen in Cotton Bolls

ZHAO Xin-Hua, SHU Hong-Mei, WANG You-Hua, CHEN Bing-Lin, ZHOU Zhi-Guo

Acta Agron Sin. 2010, 36(10):  1707-1714.  doi:10.3724/SP.J.1006.2010.01707

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Cotton has an indeterminate growth habit, the duration of growth, particularly cotton boll development period, is restricted by environmental condition. To investigate the response of the accumulation and distribution of biomass and nitrogen in cotton bolls to environmental condition and its relationship with fiber and seed quality characteristics, we carried out field experiments in Xuzhou (117°11′E, 34°15′N) and Anyang (114°13′E, 36°04′N). Using two cotton cultivars, Kemian 1 and NuCOTN, grown in the field with two sowing dates (25-Apr and 25-May) treatments. The results showed that, mean daily temperature during boll development stage in the middle fruiting branch position for the normal sowing date (25-Apr) treatment in the two sites was 24.8℃ and 24.1℃ respectively, while only 20.8℃ and 19.4℃ for the late sowing date (25-May) treatment. And when mean daily temperature was lower than 20.8℃cotton shell biomass increased while its nitrogen accumulation amount decreased in the late sowing date treatment. And for the biomass and nitrogen accumulation in fiber and cotton seed development, the start time of the rapid accumulation stage was later, the maximal rate was lower and its emergence time was later, resulting in the decrease of biomass and nitrogen accumulation amount. The maximal rate of nitrogen accumulation appeared earlier than that of biomass accumulation in fiber and that was opposite in cotton seed development. Under low temperature, biomass and nitrogen distribution indices increased in cotton shell while decreased in cotton seed, and no significant changes for nitrogen distribution indices in fiber. Boll weight, fiber strength and seed protein/oil content were also decreased in lower temperature condition. These results indicated that low temperature condition (mean daily temperature below 20.8℃) inhibits the transportation of nitrogen and photosyntheates products from plants to bolls (shell, seed and fiber), which decreases the accumulation amount of biomass and nitrogen in seed and fiber, leading to the reduction of their qualities.

Morphological and Physiological Changes in Seedling Standing and Establishment of Broadcasted Rice Seedlings

GUO Bao-Wei, CHEN Hou-Cun, ZHANG Chun-Hua, WEI Hai-Yan, ZHANG Hong-Cheng, DAI Qi-Gen, HE Zhong-Xiang, HU Ke, XING Lin, GUAN Wen-Wen, HUANG Xing-Fu, YANG Xiong

Acta Agron Sin. 2010, 36(10):  1715-1724.  doi:10.3724/SP.J.1006.2010.01715

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Seedlings standing and establishment is a special process for broadcasted rice. And whether the seedlings could establish timely is the basis of high yield. In this research, rice cultivar Nanjing 44 was adopted, and five treatments with different seedling poses and with or without soil were set artificially including the upright seedlings with soil (USWS), the leaning seedlings with soil (LESWS), the lying seedlings with soil (LASWS), the lying seedlings without soil (LASWTS), the upright seedlings without soil (USWTS). The morphological and physiological changes were studied during the process of seedling standing and establishment. Results were as follows: (1) The crown of the lying seedlings bent its lower side that produced more new roots as a pivot for standing. In the curvature zone of the lying seedling, actively elongated cells of the lower side grew faster than those of the upper side, which led to an asymmetric growth. (2) The time of seedling standing of LESWS, LSWS and LSWTS was 4 d, 8 d, and 12 d, respectively. (3) USWS and LESWS produced more roots during seedling standing period, whose activity was stronger. (4) The water content of the seedlings without soil decreased fast during the early period then increased during the later period, which was near to that of the seedlings with soil from 10 days after transplanting. (5) The chlorophyll contents of LASWS, LASWTS, and USWTS were lower than those of USWS and LESWS during the early period, those of all treatments restored to the normal level from 10 days after transplanting except LASWTS. (6) Total soluble sugar of any treatment’s roots and aboveground part was consumed at two days after transplanting, then that in aboveground plants of LASWTS and USWTS began to increase. USWS and LESWS consumed more total soluble sugar. (7) The N, P, and K accumulation increased in root and aboveground parts. The average increasing rates of N, P and K accumulation were higher in the seedlings with soil than in the seedlings without soil and also higher in the upright seedlings than in the lying seedlings. (8) Theoretical yield and practical yield were all shown as below: USWS>LESWS>USWTS>LASWS> LASWTS. And it could be concluded that, the time of seedling standing and establishment was earlier in the seedlings with soil than in the seedlings without soil and also earlier in the upright seedlings than in the leaning and lying seedlings. Therefore, in production we should choose the seedlings with soil, increase the proportion of the upright seedlings and reduce the proportion of the lying seedlings, as a result, improve the population quality for broadcasted rice.

Effect of Selection for High Yield, Drought and Salinity Tolerances on Yield-Related Traits in Rice (Oryza sativa L.)

ZHOU Zheng, LI Hong, SUN Yong, HUANG Dao-Qiang, ZHU Ling-Hua, LU De-Cheng, LI Kang-Huo, XU Jian-Long, ZHOU Shao-Chuan, LI Zhi-Kang

Acta Agron Sin. 2010, 36(10):  1725-1735.  doi:10.3724/SP.J.1006.2010.01725

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Rice production is limited by many environmental factors, of which drought and salinity are the most important abiotic stresses which greatly constrain yield and planting area of rice. Development of drought and salinity tolerant (DT, ST) varieties is a most effective method to solve this problem. Using BC₃F₅ introgression populations derived from a elite indica variety Fengaizhan 1 (FAZ1) as the recurrent parent and indica varieties Guanghui 122, Bg 94-1, and japonica varieties Yuanjing 7 and Shennong 89366 as donor parents, two high yield (HY) lines with DT, FAZ1/Guanghui 122 and FAZ1/Yuanjing 7, and two HY lines with ST, FAZ1/Shennong 89366 and FAZ1/Bg94-1, were selected and used for the pyramiding of HY and DT or ST. As compared with the pyramiding parents, DT, ST and HY lines were selected from the two pyramiding F₂ populations, getting 30–42 extreme DT, ST and HY individuals with selection intensity of 8.3%–11.7%, respectively. Under the irrigation condition, the selected populations with three target-trait all showed obvious segregations of yield-related traits including heading date, reproductive panicle number per plant, spikelet number per panicle, filled grain number per panicle, seed setting rate and 1000-grain weight. Direction of variation varied with the selected populations and the related traits. Among the six selected populations, the reproductive panicle number per plant and filled grain number per panicle had greatest contributions to yield with an average of 18.5% and a range of 12.9%–27.4% for the former an average of 13.1% and a range of 9.0%–21.2% for the latter. After intercross screening, around 10.0%–36.7% of ST lines were selected from the DT-selected populations of the two pyramiding crosses with an equivalent resistance levels as those ST-selected populations on the average, indicating that some genetic overlapping exists between DT and ST. The strategy of first screening against DT or ST then HY and further pyramiding of these three target traits from different donors is recommended for rice breeding for high yield with DT and ST.

Effects of Nitrogen Application Rates on Translocation of Dry Matter and Utilization of Nitrogen in Rice and Wheat

ZHANG Jun-Hua, LIU Jian-Li, ZHANG Jia-Bao, ZHAO Fu-Chao, CHENG Ya, WANG Wei-Peng

Acta Agron Sin. 2010, 36(10):  1736-1742.  doi:10.3724/SP.J.1006.2010.01736

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Excessive application of nitrogen-fertilizers often results in low nitrogen use efficiency and high nitrogen losses in Tai Lake region. Many studies on wheat (Triticum aestivum L.) or rice (Oryza sativaL.) physio-ecology have been carried out aiming at high yield with reasonable amount of nitrogen fertilizer. However, most experiments have been focused on single crop. Also, assimilate accumulations before flowering play an important role on grain yield. In order to disclose the mechanism of dry matter translocation, optimum amount of nitrogen application and utilization of nitrogen under rice-wheat rotations, a field experiment was conducted under different nitrogen application rates from 2007 to 2009 at the Changshu Agroecological Experiment Station, Chinese Academy of Sciences. The treatments included four nitrogen fertilizer rates for rice and wheat, respectively: N1 (125 and 94 kg N ha^-1), N2 (225 and 169 kg N ha^-1), N3 (325 and 244 kg N ha^-1), and N0 control (no nitrogen). The results showed that no significant increase in crop production was found when nitrogen application rate of rice and wheat was in excess of 225 kg ha^-1 and 169 kg ha^-1 respectively. The dry matter accumulations at anthesis of rice and wheat increased with the nitrogen rate increment, while the contribution of dry matter translocation from vegetative organs to grains before flowering decreased with increasing the nitrogen application rates. The nitrogen agronomic efficiencies and physiological efficiencies in rice and wheat were reduced with increasing the nitrogen rates, and these was no significant difference between N2 and N3 treatments. The marginal productions were declined with the increase of nitrogen applications, with lower than 5.5 kg kg^-1 in N3 treatment for both rice and wheat. Therefore, whether for rice or for wheat, the N2 treatment could maintain higher translocation rate of dry matter, higher nitrogen use efficiency and higher economic benefit.

Effects of Nitrogen Application Amount and Planting Density on Angle and Length of Top Three Leaves in Double-Cropping Rice

LIN Hong-Xin, PAN Xiao-Hua, SHI Qing-Hua, PENG Chun-Rui, WU Jian-Fu

Acta Agron Sin. 2010, 36(10):  1743-1751.  doi:10.3724/SP.J.1006.2010.01743

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An experiment was conducted with early rice Zhongzao 22 and late rice Tianyouhuazhan with split-plot design in 2007 and 2008. The results showed that the grain yield increased with increasing planting density in low nitrogen application condition, while the lower planting density was favorable to higher grain yield in higher nitrogen application condition. The lengths of the top three leaves were increased with increasing applied nitrogen amount or decreasing planting density. There were a parabolic relationship of grain yield with basal angle, opening angle and length of the top three leaves of Zhongzao 22, and with basal angle and opening angle of the top three leaves of Tianyouhuazhan, and a linear relationship of grain yield with the length of the top three leaves of Tianyouhuazhan. The optimum values of basal angle, opening angle and length of the flag leaf of Zhongzao 22 for high yield were 11.37°, 7.81°, 29.74 cm, those of the second leaf from top were 17.27°, 16.06°, 36.08 cm, and those of the third leaf from top were 21.76°, 24.70°, 39.02 cm, respectively; the optimum values of the basal angle and opening angle of the flag leaf of Tianyouhuazhan were 11.62°, 12.30°, those of the second leaf from top were 32.61°, 30.08° and those of the third leaf from top were 23.55°, 31.21°, respectively.

Physiological Mechanisms of Enhanced Uptake of Potassium Nutrition in EdHP1 (H⁺-pyrophosphatase) Transgenic Tobacco (Nicotiana tabacum)

JIN Wei-Huan, DONG Jian-Hui, CHEN Ming, CHEN Yao-Feng, LI Lian-Cheng, XU Zhao-Shi, MA You-Zhi

Acta Agron Sin. 2010, 36(10):  1752-1759.  doi:10.3724/SP.J.1006.2010.01752

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Potassium is necessary for plant growth and enhancing uptake of potassium is important to improve crop yield. In this study, previous transgenic tobacco transformed with Elymus dahuricus EdHP1 (H⁺-pyrophosphatase) was used to compare the physiological characteristics between transgenic tobacco and wild type tobacco. The results showed that under starvation of potassium, the content of K⁺ accumulated in wild-type tobacco was 62.9% of that in transgenic tobacco, and the total root length, total root surface area, and total root volume in wild type tobacco were observably lower than those in transgenic tobacco (P<0.05), with the decrease of 72.9%, 68.1%, and 60.6%, respectively. In addition, in different root systems of fine roots (diameter=0.5–2.0 mm), middle roots (diameter= 2.5–4.0 mm) and coarse roots (diameter>4.5 mm), fine roots were biggest different between transgenic and wild type tobacco which fine roots were 72.9% of those in transgenic tobacco. The activity of root system in transgenic tobacco was 1.2 times as high as that in wild type tobacco. The activity of H⁺-pyrophosphatase and the content of free IAA in wide-type tobacco were only 46.4% and 66.2% of those in transgenic tobacco respectively. The results of non-destructive ion flux measurement showed that under starvation of potassium the efflux of K⁺ from wild type tobacco was observably higher than that from transgenic tobacco, but inverse result was found efflux of H⁺ with similarly total root surface area of transgenic tobacco and wild type tobacco. Two physiological mechanisms containing well-developed root system and higher activity of K⁺ transporters enhanced uptake of potassium in EdHP1 transgenic tobacco plants.

Effects of Controlled-Release Fertilizer on Yield and Nitrogen Accumulation and Distribution in Summer Maize

ZHAO Bin, DONG Shu-Ting, ZHANG Ji-Wang, LIU Peng

Acta Agron Sin. 2010, 36(10):  1760-1768.  doi:10.3724/SP.J.1006.2010.01760

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The field experiment was conducted to investigate the effects of controlled-release fertilizers (including one kind of fertilizer enveloped by colophony, CRF, and the other kind of fertilizer enveloped by sulfur, SCF) on accumulation and distribution of photosynthate and nitrogen as well as yield after anthesis of summer maize. Results indicated that photosynthetic rate of the treatments with controlled-release fertilizers CRF and SCF kept in a higher level after anthesis. Under the same application rates of N, P, and K, applying CRF (1 428 kg ha^-1) and SCF (1 668 kg ha^-1) increased the accumulation of dry matter and nitrogen per plant significantly compared with applying the common compound fertilizer (CCF, 1 260 kg ha^-1). When the applied amounts of the CRF and SCF were decreased by 25%, the increment was also significant, and the distribution proportion of the dry matter from plant to seeds was significantly higher than that of applying CCF. The accumulation of the nitrogen in seeds of the CRF and SCF treatments was significantly higher than that of CCF treatment at maturity stage, and was increased with increasing applied proportion of fertilizer, but these was no significant difference between treatments of CRF, SCF and 25%.of CRF and SCF. Appling CRF and SCF increased the maize grain yield by 13.15% and 14.15% respectively under the same application rates. When the applied amount of CRF and SCF was decreased by 25%, the yield increment was 9.69% and 10.04%, respectively, the nitrogen use efficiency (NUE) and nitrogen agronomy efficiency were significantly higher than those of applying CCF.

Accumulation Dynamics of Glutenin Subunits and Glutenin Polymer in Wheat Cultivars with Different Qualities during Grain Development

GAO Wen-Chuan, MA Meng, WANG Ai-Na, ZHAO Hui-Xian

Acta Agron Sin. 2010, 36(10):  1769-1776.  doi:10.3724/SP.J.1006.2010.01769

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The quality of wheat (Triticum aestivum L.) flour for end use depends on the visco-elastic properties of dough, which are influenced by quantity and quality of the gluten-forming storage proteins of wheat endosperm. Gliadin and glutenin are major components of gluten protein. Dough strength is determined by the capacity of glutenin subunits to form large polymers with different sizes, and the quantity and composition of glutenin polymer influence wheat dough properties. To date, there are few reports on accumulation dynamics of glutenin subunits and glutenin polymer in wheat cultivars with different qualities during grain development. In this study, three strong-gluten and four weak-gluten wheat cultivars with different HMW-GS compositions were used to analyze accumulation dynamics of glutenin subunits and glutenin polymer during grain development. The results showed that HMW-GS and LMW-GS of strong-gluten cultivars initially expressed at 9–12 d after flowering, which were earlier than those of weak-gluten cultivars (12–15 d after flowering). Expression time of glutenin subunits in wheat cultivars with strong-gluten was a little earlier than that in wheat cultivars with weak-gluten. The quantity of HMW-GS in each cultivar rapidly increased during the early period of grain-filling, and kept stable from 27 d after flowering to maturity, however, the quantity of LMW-GS accumulated slowly during the grain-filling period, reaching stable level at 30 d after flowering. In wheat cultivars with strong-gluten, TGP (total glutenin polymer) % and GMP (glutenin macropolymer) % rapidly increased at 12–21 d after flowering and slowly increased during 21–30 d after flowering, and then maintained at the stable level from 30 d after flowering to maturity. However, in weak-gluten cultivars, TGP% and GMP% rapidly increased at 12–24 d after flowing and decreased continuously from 27 d after flowering to maturity. The differences of expression profile and accumulation of glutenin subunits and glutenin polymer between wheat cultivars with strong-gluten and weak-gluten may be the key factors affecting strong-gluten or weak-gluten formation of wheat cultivars.

Changes in the Pattern of Organization of Microtubules during Meiosis in Pollen Mother Cell (PMC) of Autotetraploid Rice

HE Jin-Hua, CHENG Xing-An, CHEN Zhi-Xiong, GUO Hai-Bin, LIU Xiang-Dong, LU Yong-Gen

Acta Agron Sin. 2010, 36(10):  1777-1785.  doi:10.3724/SP.J.1006.2010.01777

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Changes of microtubule distribution and chromosome behavior in autotetraploid rice during meiosis of PMC were detected in detail by using indirect-immunofluorescence laser scanning confocal microscopy. The result showed that microtubule distribution pattern in PMC of autotetraploid rice was similar to that of diploid rice during meiosis. But in comparison to diploid rice, different microtubule behaviors, such as longer circumferential microtubules, more spindle microtubules, were found in autotetraploid rice. At prophase I, microtubules were decreased a lot in number and distributed unevenly at leptotene. At zygotene, microtubules with no obvious polar distribution formed a diffuse network. At pachytene, nucleolus disintegration and distorted microtubules structure were found. At diplotene, no circumferential microtubule was found and microtubules depolymerization displayed in advance. At diakinesis, microtubules were decreased a lot in number. Perinuclear microtubules abnormally knitted. At MetaphaseI, many kinds of abnormalities appeared in spindle. At telophase I, phragmoplast was abnormal, and speckle microtubules were found in the cell. At telophaseII-tetra stage, two daughter cells connected, and microtubules randomly arranged in tri-fission. The results showed that microtubule abnormal reorganization pattern had a close relationship with abnormal chromosome behavior, which may act synergistically on pollen fertility and seed setting rate in autotetraploid rice.

RESEARCH ACTIVITIES

Genetic Analyses of Silk Vigor in Maize

WU Xin, CUI Zi-Tian, HU Yan-Min, LIU Zong-Hua, LI Shao-Wei, WANG Jian-Wen, TANG Ji-Hua

Acta Agron Sin. 2010, 36(10):  1786-1790.  doi:10.3724/SP.J.1006.2010.01786

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Silk vigor is an important trait that effects hybrid seed production and hybrid production in maize. For dissecting the genetic basis of silk vigor, a set of 203 recombinant inbred lines (RIL) population, which derived from the elite hybrid Nongda 108 (Huang C × Xu 178), were evaluated at three environments. The results showed that silk vigor of genotype had significant distinct at different environments. Eight different QTL were detected for silk vigor using composite interval mapping method, and located on chromosomes 3, 5, 6, 7, and 8, with 11.06%–20.82% phenotypic contribution of silk vigor, this study can aid to seed vigor selection in maize breeding.

Preliminary Analysis on Rice Blast Disease and Genetic Diversity of Its Pathogen in Multi-Genotype and Mono-Genotype Varieties

TANG Zhi-Ming, JIN Xiao-Chun, LI Xiao-Fang, LIU Yan-Zhuo, LIU Zhi-Xia, LU Dong-Bai, MAO Xin-Hua, GAO Yun, LU De-Cheng

Acta Agron Sin. 2010, 36(10):  1791-1795.  doi:10.3724/SP.J.1006.2010.01791

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The haplotypes of rice blast disease (Magneaporthe grisea) were obtained and analyzed in the multi-genotype and mono-genotype variety groups by DNA fingerprinting with rep-PCR. The isolates of Magneaporthe grisea were classified into several haplotypes. It was found that the diversity index of blast pathogen ranged from 0.521 to 0.603 in multi-genotype varieties, and from 0.319 to 0.705 in mono-genotype varieties. The diversity index of blast pathogen was lower in susceptible varieties and higher in resistant ones. However, there was no difference in the diversity of rice blast fungi between the two variety groups. The disease rate of panicle-neck blast in multi-genotype varieties was remarkably lower than the weighed average value of disease rates in percentage of their components in mono-genotype varieties. The diversity of isolates in both multi-genotype varieties and mono-genotype varieties was not different, but the resistant component of the multi-genotype varieties blocked spore dispersal of the causal fungus and reduced the disease. So using the multi-genotype varieties is a good approach to control the rice blast.

Physiological Characteristics of drought-Sensitive and Drought-Insensitive Rice Maintainers at florescence under Drought Stress

TAO Long-Xin, FU Guan-Fu, SONG Jian, XIONG Jie, LE Ming-Kai, WANG Xi

Acta Agron Sin. 2010, 36(10):  1796-1803.  doi:10.3724/SP.J.1006.2010.01796

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Drought tolerance traits of 14 widely used Chinese rice maintainers were evaluated at flowering stages using both soil moisture meter and drying soil methods. Based on their drought-stress-caused fertility injury and water-supplying remedy, four ranks were classified as drought-insensitive, drought-resistant, drought-friability and drought-sensitive. Typical drought-insensitive maintainers K22-B, Jin 23-B and typical drought-sensitive maintainers Zhenshan 97-B, Zhong 9-B were selected to suffer drought treatments and to study their physiological responses to drought. The results indicated that the water potential of reproductive organs and flag-leaf transpiration rate were decreased by drought, but when compared with the drought-sensitive maintainers, the drought-insensitive maintainers showed a higher water potential which was decreased relatively slower with drought enhancing. There was no difference of photosynthetic rate between drought-insensitive and drought-sensitive maintainers under normal water condition, but the photosynthetic rate was decreased by drought treatment, and the decreases were bigger for drought-sensitive maintainers than for drought-insensitive maintainers. There was no significant difference between the two types of maintainers in pollen and anther number in drought condition (P>0.05), and in pollen-fullness and germination rate on stigma. However, pollen number on stigma and opening degree of anther were decreased more in drought-sensitive maintainers than in drought-insensitive maintainers. Therefore, the drought-insensitive maintainers have a higher photosynthesis and higher photosynthate transportation efficiency than drought-sensitive maintainers.