Table of Content

12 March 2011, Volume 37 Issue 03

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Mapping QTLs for Seminal Root Architecture and Coleoptile Length in Wheat

LIU Xiu-Lin, CHANG Xiao-Peng, LI Run-Zhi, JING Juan-Lian

Acta Agron Sin. 2011, 37(03):  381-388.  doi:10.3724/SP.J.1006.2011.00381

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Root system is important for belowground nutrients acquisition, and is also an important part to respond to drought stress. The purpose of this study was to dissect the genetic basis of seminal root architecture and coleoptile length of wheat by mapping quantitative trait loci (QTLs) of target traits. A doubled haploid (DH) population with 150 lines derived from a cross between two common Chinese wheat varieties Hanxuan 10 and Lumai 14 was used as the plant materials. Gel-chamber was employed to evaluate seminal root architecture traits, including maximum root length (MRL), root number (RN), total root length (TRL), root diameter (RD), root angle (RA), ratio of root dry weight to shoot dry weight (RDW/SDW), and coleoptile length (CL) of seedlings. QTLs for these traits were detected using mixed-model-based composite interval mapping method. A total of 12 additive-effect QTLs and 7 pairs of additive × additive QTLs associated with the target traits were mapped on chromosomes 1A, 1B, 2B, 2D, 3B, 4A, 4D, 5A, 5B, 6A, 7A, and 7B. The phenotypic variation explained by individual additive-effect QTL varied from 5.64% to 12.37%. The additive effects ranged from 0.20 to 7.45. The phenotypic variation explained by each pair of epistatic QTLs varied from 8.70% to 15.90%. Two QTL clusters for seedling root traits were detected on chromosomes 3B and 7A. These results would be helpful to maker-assisted selection of seminal root architecture and coleoptile.

Genetic Effects and Diagnosis of Premature Senescence of Leaf in Upland Cotton

HAO Jun-Jie, LIU Huan-Min, MA Qi-Xiang, CUI Xiao-Wei, XU Ji-Wen, GU Xin-He, GAO Jun-Shan

Acta Agron Sin. 2011, 37(03):  389-396.  doi:10.3724/SP.J.1006.2011.00389

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Premature senescence of cotton has been occurring on an increasing scale in China, directly influencing both yield and fiber quality. The most effective way avoiding premature senescence is to obtain stay-green variety in breeding programs. Moreover, plant breeders demand a simple and efficient diagnosis method, and farther understand the genetic basis of premature senescence in cotton. The objective of this paper was to discuss the quick measurement harmless to plant, and to analyze the genetic effects for leaf premature senescence in upland cotton. The SPAD readings of the fourth leaf from the top were measured at the flowering day and also each five days after flowering in nine cotton varieties (lines). The SPAD readings at 35 days after flowering (DAF) were decreasing in premature  senescence cotton varieties (lines). Therefore, the SPAD difference between 35 DAF and the flowering day was calculated as an indicator of the reduction in chlorophyll content; the greater the rate of reduction, the earlier the senescence, and vice versa. The degree of leaf premature senescence was expressed by the reduction of SPAD or the scale of the green-area in generations (P₁, F₁, P₂, F₂, BC₁, and BC₂) of the 33B×CJ463 cross. Generation mean analyses were conducted to explain the inheritance of leaf premature senescence. The results showed the relative importance of additive effects controlling leaf premature senescence. The estimated minimum number of genes controlling leaf premature senescence was an additive major allele at least with relatively high heritability, suggesting the early selection for late-senescence varieties (lines) was effective in the offspring. The relationships between premature senescence and leaf area per plant were different in the different segregating generations. In a few words, the results of genetic analysis and the relationships between premature senescence and leaf area measured by the reduction of SPAD and the scale of the green-area were relatively consistent.

Analysis of T-DNA Flanking Sequences and Event Specific Detection of Transgenic Alfalfa with Gene BADH

ZHANG Yan-Min, ZHANG Hong-Mei, XIANG Jin-Yang, GUO Xiu-Lin, LIU Zi-Hui, LI Guo-Liang, CHEN Dao-Yi

Acta Agron Sin. 2011, 37(03):  397-404.  doi:10.3724/SP.J.1006.2011.00397

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The gene encoding betaine aldehyde dehydrogenase (BADH), an important osmoregulation gene, has been transformed into many crops, including wheat (Triticum aestivum L.), rice (Oryza sativa L.), maize (Zea maysL.), rape (Brassica campestris L.), and potato (Solanum tuberosumL.). Transgenic crops carring BADH gene enhances tolerance to salinity and drought stresses. Gene badh had been integrated into the most important forage crop alfalfa (Medicago sativa L.) in our previous work, and 42 transgenic plants with improved salt tolerance were obtained. Since they were derived from the same transformant vector, these plants were not able to be distinguished from each other by commonly used methods, such as screening detection, gene specific detection, and vector specific detection. To differentiate these transformants in molecular level, we performed the thermal asymmetric interlaced PCR (TAIL-PCR) to separate the T-DNA flanking sequences for identification of the transgenic plants in event specific detection. A total of six sequences flanking either the left or the right borders of the T-DNA were obtained, which included the flanking sequences at both left and right borders of plant B127, and the left border flanking sequences of plants B125, B138, B295, and B196. The left border sequence of T-DNA was completely deleted from the vector and was thus not integrated into the genome of alfalfa in the transgenic plant B196. Although the left border flanking sequence in the transgenic plant B127 was not changed, it was filled with a DNA sequence of unknown origin. The forward and backward primers for PCR were designed based on the characteristics of the flanking sequences originating from the vector sequence and the alfalfa genomic sequence adjacent to the integrated vector sequence, respectively. The results of amplification in 42 BADH-transgenic alfalfa plants showed that plants B106, B125, B127, B138, B157, B158, B289, B295, and B305 presented the same amplification banding patterns. Plants B196, B203, B220, and B223 produced the same banding pattern which was different from that in other plants. These results indicated that the plants with identical amplification banding pattern may come from the same transformation event. Based on the findings in the present study, we successfully used the flanking sequences separated by TAIL-PCR analysis in developing event specific detection method, which can be used not only to differentiate the origins of various transformants, but also to distinguish the transformants from each other. It is useful in protection of transgenic crops and labeling of transgenic products.

Identification of Marker Genotypes Associated with Elite Combining Ability for Quality Traits in Parents of Hybrid Japonica Rice (Oryza sativa L.)

HUANG Dian-Cheng, LIANG Kui, SUN Cheng, JIANG Jian-Hua, SHI Meng-Liang, DAI Jian, XIE Hui, ZHAO Kai-Ming, RUAN Fang-Song, MA Wen-Xia, HONG De-Lin

Acta Agron Sin. 2011, 37(03):  405-414.  doi:10.3724/SP.J.1006.2011.00405

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The area planting japonica hybrid rice is only 3% of the total area (8.28´10⁶ ha) of japonica rice. One of the reasons why japonica hybrid rice popularized slowly is that grain quality of hybrid was inferior to that of conventional cultivars. In order to improve grain quality combining ability of parental lines more efficiently, SSR marker genotypes of elite combining ability for 10 quality traits, namely, brown rice rate (BRR), milled rice rate (MRR), head rice rate (HRR), grain length (GL), grain width (GW), percentage of chalky grain (PCG), chalkiness degree (CD), gelatinization temperature (GT), gel consistency (GC) and amylose contents (AC), were identified in this study, by analyzing the data of combining ability and SSR markers in six CMS lines and twelve restorer lines, which were genotyped using 115 pairs of SSR primers. A total of 30 SSR marker genotypes were significantly associated with combining ability of the 10 quality traits. Twenty-five of them were marker genotypes for unfavorable combining ability of quality traits. The remaining five marker genotypes were associated with elite combining ability for quality traits of parents. RM263-175/180 and RM444-230/240 were marker genotypes of elite combining ability for HRR, which increased 3.2% and 2.5% of HRR in F₁, respectively. RM3-120/150 shortened GL value in F₁ by 2.4%. RM444-180/240 increased GW trait value of F₁ by 2.1%. RM428-273/294 decreased AC trait value of hybrid rice harvested from F₁ plants by 7.0%. Among the SSR marker genotypes associated with combining ability of the 10 quality traits, eight marker genotypes also affected combining ability of yield components simultaneously. RM3-120/150 increased simultaneously total spikelets per plant (TSP) and filled spikelets per plant (FSP) in F₁ by 15.9% and 10.9%, respectively. RM1211-150/160 decreased trait values of BRR and MRR in F₁ by 0.9% and 1.1%, respectively, and simultaneously increased trait values of TSP and FSP in F₁ by 21.8% and 20.4%. RM23-150/160 increased trait values of PCG and CD in F₁ by 44.1% and 45.7%, and simultaneously increased daily yield per plant and TSP in F₁ by 11.2% and 11.6%, respectively. These results could be used for directing improvement of combining ability of parents for quality traits and yield traits through the marker-assisted selection, and for determining parents for making combinations of hybrid japonica rice in the future.

Correlation between AhFAD2 Polymorphism and Oleic Acid/ Linoleic Acid (O/L) Ratio in Peanut Seeds

ZHOU Li-Xia, TANG Gui-Ying, CHEN Gao, BI Yu-Ping, SHAN Lei

Acta Agron Sin. 2011, 37(03):  415-423.  doi:10.3724/SP.J.1006.2011.00415

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Peanut oils containing high levels of oleic acid and low linoleic acid levels are strongly demanded. This would improve oil stability and nutritional quality. Thus, breeding peanut variety with high O/L ratio has become one of the major goals in plant breeding. To investigate the genetic traits that control high oleate levels-phenotype and improve the peanut-breeding efficiency, we sequenced ORF region of about 527 delta 12 fatty acid desaturaseAhFAD2 cDNAs from 13 peanut varieties. Our results showed that three types of mRNA transcripts AhFAD2A, AhFAD2B and pseudogene existed in all peanut varieties. Genotypes of peanut varieties TaishanPearl, Taishan Sanlirou, Jiangtian, Chico, 05-21063, Baisha 1016; and Linguimake, Feilongxiang, Goule, Luhua 14, Huayu 19, Huayu 23, and Luhua 11 were found to be OL1OL1OL2OL2, ol1ol1OL2OL2 and OL1ol1OL2OL2, respectively. We also found thatsome SNP polymorphism sites existed in the AhFAD2A gene but not in all peanut varieties, and AhFAD2B was relatively conserved in all 13 peanut varieties investigated. Combined with the measurement of O/L ratio in various peanut varieties, the relationship between gene polymorphism and O/L ratio was primarily investigated. Meanwhile, the potential function of pseudogene was also discussed.

Cloning and Functional Analysis of Enoyl-CoA Reductase Gene BnECR from Oilseed Rape (Brassica napus L.)

NI Yu, ZHANG Fei-Cui, WANG E-Chao, BO Fei, WANG Rui, CHAI You-Rong, LI Jia-Na

Acta Agron Sin. 2011, 37(03):  424-432.  doi:10.3724/SP.J.1006.2011.00424

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Very-long-chain fatty acids (VLCFAs) are critical components found in cuticular waxes, sphingolipids and triacylglycerols in higher plants. Biosynthesis of VLCFAs is catalyzed by the fatty acyl-CoA elongase, a membrane-bound enzymatic complex containing 3-ketoacyl-CoA synthase (KCS), 3-ketoacyl-CoA reductase (KCR), 3-hydroxacyl-CoA dehydratase (HCD), and trans-2, 3-enoyl-CoA reductase (ECR). In this research, primers were designed based on multiple alignments of trans-2,3-enoyl-CoA reductase (ECR) gene sequences from Arabidopsis thaliana and other plants, and the full- length cDNA, here designated BnECR, and the corresponding genomic sequenceswere isolated from Brassica napus by using rapid amplification of cDNA ends (RACE) method (GenBank Accession No. FJ899705 and FJ899705). The sequence of BnECR cDNA was 1 328 bp (excluding the poly dA tail), and the corresponding genomic sequence was 2093 bp. BnECR was composed of four exons and contained a 163 bp 5' untranslated region (5' UTR) and a 233 bp 3' UTR. The deduced BnECR protein was 310 amino acid in length, with a MW of 735.78 kD and a pI of 9.52. The critical functional sites K₁₄₄, R₁₄₅ in AtECR were unchanged in BnECR. The G₂₂₅SGGYQIPR/HG₂₃₄ which presented a non-classical NADPH-binding motif was found in C-terminal of BnECR. NCBI Blastn, multiple alignments and conserved domain search showed that BnECR had the highest homology to A. thaliana AtECR. RT-PCR analysis showed that BnECR was ubiquitously expressed in B. napus and preferentially expressed in the stem. The transcript level of BnECR at middle and late stages of seed development in low erucic acid rapeseed cultivar was obviously lower than that in high erucic acid rapeseed cultivar, suggesting that BnECR was involved in biosynthesis of erucic acid. The 933 bp BnECRORF was subcloned into the yeast-E. coli shuttle vector pYES2.0. And then the recombinant plasmid was transformed into Saccharomyces cerevisiae wild type strain By4743 and mutant strain YDL015c, respectively. With galactose as inducer, the transformant was cultured to induce the expression of BnECR. The GC result indicated that BnECR was overexpressed effectively in S. cerevisiae, and the content of erucic acid reached to 1.34% of the total fatty acid in recombinant strain, an increase of 52% over the control. Functional complementation of BnECR in a ECR-deficient mutant yeast demonstrated that BnECR mediated the biosynthesis of VLCFAs. Our results suggest that BnECR should be functional orthologue of AtECR.

QTL Analysis on Yield and Its Components in Upland Cotton RIL

ZHANG Wei, LIU Fang, LI Chao-Hui, WANG Wei, WANG Chun-Yang, ZHANG Xiang-Di, WANG Yu-Gong, SONG Guo-Li, WANG Kun-Bei

Acta Agron Sin. 2011, 37(03):  433-442.  doi:10.3724/SP.J.1006.2011.00433

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The genetic linkage map of SSR, constructed by mixed linear model composite interval mapping with CRI-G6 (Acala 1517 × Dezhou 047) population was used to detect and localize QTLs, including main-effect QTLs, epistasis QTLs and Q×E interaction effects in order to provide information applicable to cotton MAS (molecular marker assisted selection breeding). In a separate analysis, 24 major QTLs for yield traits were identified in the three different years. Each stable major QTL was detected for seed yield, lint yield, lint percentage, seed index and bolls per plant, respectively. Fourteen main-effect QTLs and 20 pairs of additive-additiveepistasis QTLs were detected by joint analysis in three years，among them six main-effect QTLs and seven pairs of additive-additive epistasis QTLs interacted with environments. These stable main-effect QTLs with a large effect (accounting for over 10% of phenotypic variation), which were scanned in different years and linked closely with markers, can be used for MAS in high-yield breeding program.

Analysis of Adaptability of Soybean Mini Core Collections in Huang-Huai Region

LIU Zhang-Xiong, YANG Chun-Yan, XU Dan, LU Wei-Guo, QIAO Yong, ZHANG Li-Feng, CHANG Ru-Tian, QIU Li-Juan

Acta Agron Sin. 2011, 37(03):  443-451.  doi:10.3724/SP.J.1006.2011.00443

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Accurate identification and evaluation of germplasm can enhance its effective use. To evaluate germplasm’s environmental adaptability and stability, we applied the additive main effects and multiplicative interaction (AMMI) model to analyze the two years’ data of the 60 mini core collections of soybean in three provinces in the Huang-Huai region. The results showed that the interactions between the genotypes and environment (G×E) for plant height, effective branch number, 100-seed weight, and yield per unit area were highly significant (P<0.01), and the squares of G×E to total squares were 16.73%–24.57%, suggesting a need of further analysis for the stability of varieties.  The phenotypes of different varieties were dependent on the planting sites, and some germplasm performed wide adaptability while others not in particular environment. The results laid a theoretical foundation to effectively use mini core collection for breeding in Huang-Huai region.

Inheritance of Lodging Resistance Index and Its Correlations with Culm Traits in Wheat

TAO Jin-Bao, ZHANG Ping-Ping, REN Li-Juan, YANG Xue-Ming, MA Hong-Xiang, YAO Guo-Cai, ZHANG Peng, ZHOU Miao-Ping

Acta Agron Sin. 2011, 37(03):  452-458.  doi:10.3724/SP.J.1006.2011.00452

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Lodging is a big problem in wheat (Triticum aestivum L.) production, which severely influences wheat yield and quality. Lodging resistance varies among wheat varieties, and its inheritance has been rarely studied yet. The objecive of this study was to explore the genetic mechanism of culm lodging resistance index (CLRI) and its correlations with culm traitistics. Using seven wheat cultivars with diverse resistance to lodging (CLRI varying from 6.31 to 13.87), 21 crosses were obtained by the Griffing diallel-cross design. Parents Yangmai 9 and Ningmai 8 had the largest general combining ability for CLRI and significantly increased the CLRI in their crossing progenies. The inheritance of CLRI was in agreement with the additive–dominance model. Both additive and dominant effects were significant, and dominant effect was more important than the additive effect. The degree of dominance was from complete dominance to superdominance. The alleles increasing CLRI were recessive. The frequencies of alleles that increased or reduced CLRI were not significantly different among the seven parents. Yangmai 9 and Ningmai 8 had more recessive genes controlling CLRI, while Wangshuibai and Sumai 3 had more dominant genes. CLRI might be controlled by three or four pairs of major recessive genes with moderate narrow sense heritability. Correlation analysis showed that CLRI was positively correlated with diameter of the second basal internode (r = 0.4062, P < 0.05), filling degree of the first basal internode (r = 0.7743, P < 0.01), and filling degree of the second basal internode (r = 0.8712, P < 0.01); but negatively correlated with length of the first basal internode (r = -0.7064, P < 0.01), length of the second basal internode (r = -0.8182, P < 0.01), length of internode below spike (r = -0.8432, P < 0.01), plant height (r = -0.8737, P < 0.01), and height of gravity center (r = -0.9259, P < 0.01). Yangmai 9 and Ningmai 8 are recommended as important parents in logding-resistant breeding. Because CLRI is controlled by recessive genes and its narrow sense heritability is moderate, a relatively large population is suggested in early breeding generations and the phenotypic selection should not be too intensive.

Effects of SNP on AhSAG and AhBI-1 Genes Expression and Amelioration of Aluminum Stress to Peanut (Arachis hypoganea L.)

ZHAN Ji, WANG Tian-Ju, HE Hu-Yi, LI Chuang-Zhen, HE Long-Fei

Acta Agron Sin. 2011, 37(03):  459-468.  doi:10.3724/SP.J.1006.2011.00459

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Recent researches have found that NO (nitric oxide) plays an important role in mediating some biotic and abiotic stress-induced oxidative stresses in plant kingdom. Meanwhile, Al toxicity is a major constraint for crop production in acidic soils worldwide, especially in southern China. In order to enucleate the control effects of NO (nitric oxide) on aluminum (Al) stress, we researched the effects of exogenous NO donor (sodium nitroprusside, SNP) on rootelongation and relative gene expression when Al-induced PCD in root tips happened with peanut (Arachis hypoganea L.) as material. The results of root elongation, hematoxylin dying and root tips Al^{3+ content detection showed that suitable exogenous NO could alleviate Al toxicity on root tips of peanut, especially at 1.0 mmol L–1 SNP. Compared with the control, SNP at 1.0 mmol L–1 increased root growth 45% and 52%, decreased Al3+ content of root tips 10% and 23% in 99-1507 and Zhonghua 2, respectively, in the meanwhile, the color of root tips with hematoxylin dying became light. Compared to Al stress only, relative expression of AhSAG gene in 99-1507(Al-resistant) increased firstly, than decreased after adding SNP at 1.0 mmol L–1, it decreased significantly in 0.1 and 0.4 mmol L–1 Al treatments, while that inZhonghua No.2 increased slowly, it increased significantlyin 0.1 and 0.4 mmol L–1 Al3+ treatments. Compared with Al stress only, relative expression of PCD-related AhBI-1 gene in 99-1507 increased firstly, than decreased after adding SNP at 1.0 mmol L–1, but that in Zhonghua 2 had a reverse change. The relative expression of AhBI-1 gene was lower in Al+SNP treatmentsthan in Al treatments only at 0 and 0.02 mmol L–1 in 99-1507, and at 0, 0.02, and 0.1 mmol L–1 in Zhonghua 2. The results showed that NO can alleviate Al toxicity in peanut, and it maybe relate to theregulationof the expression of programmed cell death related genes, while controls the programmed cell death.}

Analysis of Epistatic and Additive Effects of QTLs for Grain Shape Using Single Segment Substitution Lines in Rice (Oryza sativa L.)

ZHAO Fang-Ming, ZHANG Gui-Quan, ZENG Rui-Zhen, YANG Zheng-Lin, LING Ying-Hua, SANG Xian-Chun, HE Guang-Hua

Acta Agron Sin. 2011, 37(03):  469-476.  doi:10.3724/SP.J.1006.2011.00469

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It is important to accelerate breeding process by pyramiding genes purposefully with molecular marker-assisted selection methods. Additive and epistatic effects of genes are the key to the success in genes pyramiding breeding. In this paper, additive and epistatic effects of QTLs for rice grain shape were analyzed using 16 single segment substitution lines (SSSL) and 15 double segment substitution lines (DSSL). A total of nine QTLs were identified on the Chromosomes 2, 3, 4, and 10 respectively, containing four for grain length, one for grain width and four for ratio of grain length to width. Furthermore, seven pairs of digenic interactions were detected for the grain shape. Among them, three interactions occurred between two loci with obvious effects on the traits, one interaction did not have obvious effects at both two loci, and three interactions occurred between one locus with and another without main effect at the single-locus level. Again, the results also indicated that the epistatic effects were different when the same QTL controlling grain length was pyramided with various SSSLs. Only when the epistatic effects were syntropic with the additive effects of the target genes, the pyramiding effect could be obvious. Moreover, longer or shorter grain was difficult to be obtained by pyramiding two QTLs controlling long grain or two QTLs for short grain. The results are important for improving grain shape by molecular marker assisted selection.

Genetic Overlap of Drought-Tolerance Loci between Germination Stage and Seedling Stage Analyzed Using Introgression Lines in Soybean

QIU Feng-Cheng, ZHANG Wen-Bo, LI Can-Dong, JIANG Hong-Wei, LIU Chun-Yan, FAN Dong-Mei, CENG Qiang-Li, HU Guo-Hua, CHEN Qiang-Shan

Acta Agron Sin. 2011, 37(03):  477-483.  doi:10.3724/SP.J.1006.2011.00477

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Soybean grows worldwide in many regions under drought stress, so drought tolerance (DT) is a very important trait for the crop. Most researches have focused on the QTL mapping related with drought-tolerance, but there is no research on the genetic overlap in soybean. A primary backcross introgression lines (ILs) were constructed with Hongfeng 11 as recurrent parent and Clark as donor parent. Forty-four individuals from BC₁F₅ introgression populations were screened out under drought stress comparing with the Hongfeng11 in germination stage, and 46 individuals were obtained under drought stress comparing with the control population in seedling stage. The QTL identification at germination stage and seedling stage was conducted by one-way ANOVA (for single marker analysis, P<0.05) with the two introgression populations. Then 10 QTLs were mapped in germination stage, 21 QTLs were mapped in seedling stage laced on relative water content(RWC)，water holding capacity(WHC), and growth of plant height(GPH). Four QTLs including Satt449, Satt499, Satt440, and Sat_180 in A1, K, I, and H linkage groups were mapped both in germination stage and seedling stage, indicating a partial genetic overlap between these two stages in soybean. The above results would provide a basic for fine mapping and molecular breeding for favorable genes related to DT in soybean.

Transgenic Tobacco Plants Resistant to Two Viruses via RNA Silencing

NIU Ya-Bing, WANG De-Fu, YAO Min, YAN Zhao, YAO Wen-Xin

Acta Agron Sin. 2011, 37(03):  484-488.  doi:10.3724/SP.J.1006.2011.00484

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RNA silencing is a phenomenon of homologous RNA degradation induced by dsRNA, which is an effective strategy to obtain virus resistant plants so far. By means of this strategy, higher bio-security immune transgenic plants were obtained, avoiding recombining and transcapsidating with other virus genes. In this study, the recombinant plant expression vector pBIN438-MP- Rep(i/r)consisting the inverted repeat of TMV-ΔMP and CMV-ΔRep fusion fragment was transformed into tobacco cultivar K326 via Agrobacterium-mediated. The transformants were selected in the culture medium with 100 mg L^–1 Kan. One hundred and ninety-six transgenic plants were obtained, One hundred and twenty-eight of which were positive plants, and the resistance to CMV and TMV was tested at the degree of virus. PCR-Southern blot and RT-PCR analysis of the transgenic plants demonstrated that the exogenous DNA was integrated into the tobacco genomic DNA and was expressed in transcriptional level. Resistance assay indicated that about 20.3% transgenic plants were immune to the co- infection with TMV and CMV. This result will provide to crops an important reference for plant anti-viral breeding and for preventing the viral co-infection.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Physiological Characteristics Associated with Fiber Development in Two Different Types of Natural Colored-Cotton Cultivars

ZHANG Xiang, LIU Xiao-Fei, LV Chun-Hua, DONG Shao-Di, CHEN Yuan, CHEN De-Hua

Acta Agron Sin. 2011, 37(03):  489-495.  doi:10.3724/SP.J.1006.2011.00489

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The objective of this study was to investigate the physiological characteristics of fiber in the subtending leaf of natural colored-cotton in fiber development, and to provide theoretical basis for improvement of natural colored-cotton fiber quality using brown cotton cultivar Xiangcaimian 2, green cotton cultivar Wanmian 39, and white fiber control Sumian 9 by measuring the changes of metabolite and enzyme activities. The results showed that compared with the control, fiber cellulose accumulation for Xiangcaimian 2 and Wanmian 39 was lower, changing with an “S” curve, which could be simulated well by Richards equation with a fitting coefficient of above 0.999. Maximum accumulation, accumulative rate parameter and maximum accumulative rate for cellulose of colored cotton were all lower than those of white cotton. SPAD, soluble sugar content, activity of sucrose invertase in leaf and sucrose invertase, sucrose synthase (SS), UGPase activities in fiber for colored cotton were smaller than those for white cotton. As a result, there were no enough nutrients for fiber development and the fiber quality was worse. By correlation analysis, SS and UGPase activities and the GA₃ content in fiber for colored cotton were significantly and positively correlated with fiber maturation and fiber strength (r＝0.884^*, r＝0.895^*；r＝0.914^*, r＝0.935^*; r＝0990^*, r＝0.988^*), indicating that lower metabolite and enzyme activities in natural colored-cotton led to worse fiber quality.

Comparison of Physiological and Biochemical Characteristics Related to Cold Resistance in Sugarcane under Field Conditions

ZHANG Bao-Qing, YANG Li-Tao, LI Yang-Rui

Acta Agron Sin. 2011, 37(03):  496-505.  doi:10.3724/SP.J.1006.2011.00496

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In order to screen the cold tolerant sugarcane varieties, in Ziyuan County, one of the coldest counties having longest duration for frost and snow, in Guangxi province we comprehensively evaluated 21 sugarcane varieties using subordinate function method combined with correlation analyses based on six physiological and biochemical indexes relevant to cold tolerance under natural conditions. It was found that different sugarcane varieties had different responses to the long duration of continuous cold stress, which were dull for soluble protein content proline and malondialdehyde were contents. Based on the analysis by subordinate function method, we divided the tested varieties into three groups of cold tolerance. The group I had four varieties with high cold tolerance, the group II had ten varieties with moderate cold tolerance, and the group III had seven varieties with low cold resistance. It is feasible to evaluate the cold resistance at processing maturing stage by using subordinate function method with multiple physiological and biochemical indexes, which can reveal the differences of cold hardiness in different sugarcane varieties, and provide good references for commercial sugarcane production.

Effect of Temperature at Different Durations after Anthesis on Rice Quality and Variations between Positions on a Panicle

DONG Ming-Hui, CHEN Pei-Feng, JIAO Zhong-Ying, TUN Xiang-Zhou, ZHAO Bu-Hong, JIANG Yuan-Yuan, YANG Jian-Chang

Acta Agron Sin. 2011, 37(03):  506-513.  doi:10.3724/SP.J.1006.2011.00506

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The aim of this study was to investigate the effect of high temperaturesimposed at early and mid grain filling stages on the quality of grains at different positions on a panicle, and to seek cultivation techniques to improve rice quality. Two rice cultivars, Yangdao 6 (indica) and Yangjing 9538 (japonica), were pot-grown and subjected to high (35℃) temperatures during the initial (0–10 d) and mid (10–20 d) grain filling stages after anthesis. Compared with atmospheric temperature (25–27℃, CK), the high temperature treatments significantly affected grain quality. Generally, the influence of the temperature treatment at the initial filling stage was more than that at the mid filling stage, however, the grain quality varied with cultivars and grains positions. High temperatures imposed at early and mid grain filling stages reduced brown rice rate (BRR), head rice rate (HRR), head milled rice rate (HMRR), but increased crude protein content (CPC), and the grains on primary branches were affected more than those on secondary branches, and later-flowered grains were affected more than early-flowered grains. High temperature imposed at the early grain filling stage significantly increased chalkiness degree (CD) and chalky grain percentage (CGP) of early-flowered grains at the same branch; high temperature treatments imposed at the early grain filling stage decreased amylose content (AC), and grains on primary branches were affected more than those on secondary branches.Sensitive of grain quality to temperature varied with cultivars and treatment times after anthesis. The influence of temperature on rice quality was more at the early grain filling than at the mid filling stage. Some cultural practices, such as balanced fertilization, arrangement of sowing date, and precise irrigation, would alleviate the influence of high temperature on rice quality.

Effect of Conservation Tillage on drymatter accumulating and Yield of Winter Wheat in Oasis Area

LI Ling-Ling, HUANG Gao-Bao, QIN Shu-Gao, YU Ai-Zhong

Acta Agron Sin. 2011, 37(03):  514-520.  doi:10.3724/SP.J.1006.2011.00514

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Hexi Oasis area is the most important region for food crop production in Gansu province, where is not only exposed to serious wind erosion but also one of the main sources of dust storm in China. Spring wheat traditionally dominates in wheat production in this area, but the bare field from dry winter to spring usually accelerates serious wind erosion. Conservation tillage proves to be able to increase water use efficiency (WUE) and eliminate soil erosion. In this study, dry matter accumulating, yield and WUE of winter wheat under different tillage practices were investigated in order to establish proper systems of conservation tillage in the Hexi Oasis area for winter wheat production, to save water and prevent wind erosion. Experiments on five tillage practices were carried out from 2004 to 2007, including conventional tillage (T), conventional tillage with stubble incorporated (TIS), no-tillage (NT), no-tillage with stubble retention (NTS), and no-tillage with stubble standing (NTSS). The effects of conservation tillage on dry matter dynamics, grain-filling characteristics, grain yield, yield components, and WUE of winter wheat were determined using wheat cultivar Fan-13. Compared with treatment T, the growth and development process and grain-filling duration of winter wheat were prolonged in NTS and NTSStreatments. Both treatments had higher values in dry matter, relative growth rate (RGR), grain-filling duration, average filling velocity in spike of main stem, and filling index than other treatments. Although the grain number per spike and 1000-grain weight of NTS and NTSS varied across years, they generally showed higher levels than those of the T and TIS treatments, especially the NTSS treatment. The highest WUE was observed in the NTS treatment. The average grain yields (2004–2007) of NTS and NTSS were increased by 18.6% and 23.8% compared to the T treatment, and the average WUE (2005–2007) of NTS and NTSS were enhanced by 26.8% and 16.1%, respectively. It is concluded that winter wheat cultivation with NTS or NTSS system could be applicable in Hexi Oasis area to obtain relative high yield and high WUE, and the field coverage with wheat seedlings during the winter could be propitious to controlling the frequency of dust storm in China.

Influence of Drought Stress on Plant Growth and Photosynthetic Traits in Maize Seedings

ZHANG Ren-He, XUE Ji-Quan, PU Jun, ZHAO Bing, ZHANG Xin-Hua, ZHENG You-Jun, BO Ling-Duo

Acta Agron Sin. 2011, 37(03):  521-528.  doi:10.3724/SP.J.1006.2011.00521

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The responses of plant growth, gas exchange and chlorophyll fluorescence parameters were studied in two different maize hybrids Zhengdan 958 (drought resistant) and Shaandan 902 (drought-sensitive) under three different drought stresses (mild drought, moderate drought, severe drought) and normal irrigation in a pot experiment. The results showed that drought stress inhibited plant growth and relative growth rate in the two hybrids, resulting in a significant decline in biomass. With the increasing of drought stress, the maximum leaf net photosynthetic rate (P_nmax), apparent quantum efficiency (AQY), light saturation point (LSP), stomatal conductance (G_s), stomatal limitation (L_s), maximum electron transport rate (ETR_m), photosynthetic efficiency (α), PSII actual quantum yield (Φ_PSII) and photochemical quenching (q_P) decreased, while the intercellular CO₂ concentration (C_i), light compensation point (LCP) and non-photochemical quenching (q_N) increased. But the change extents of all parameters were smaller in Zhengdan 958 than in Shaandan902. This finding indicated that drought stress could significantly decrease the biomass of two maize varieties, possibly caused by reduction in the photosynthetic efficiency of plants. The drought stress damaging effects on plant growth and photosynthesis were minimal on the Zhengdan 958 compared to Shaandan 902. Under drought stress the Zhengdan 958 maintained higher photosynthetic efficiency, stronger light energy transfer capacity and greater relative growth rate that may be the major physiological traits in the adaptive capacity to drought conditions.

Comparison of Kernel Starch Accumulation and Related Enzyme Activities among Six Maize Cultivars of Different Yield Types

ZUO Zhen-Peng, TIAN Feng-Long, JIANG Peng, WANG Jing, MA De-Chao, MA Jiang, LI Dong, SUN Qiang-Quan, DONG Shu-Ting

Acta Agronomica Sinica. 2011, 37(03):  529-536.  doi:10.3724/SP.J.1006.2011.00529

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Six maize cultivars were used to study the difference of the related enzyme activities in kernel starch accumulation and starch synthesis among different yield cultivars. Sucrose synthase(SS), UDPG pyrophosphorylase (UGPase) and starch branching enzyme(SBE) were the key enzymes in maize starch synthesis. High activities of SS, UGPase and SBE were beneficial to the accumulation of starch and the improvement of kernel weight. The time of amylose accumulation in low yield cultivars(LYV) (30 d) was shorter than that in middle yield cultivars(MYV) (40 d) and high yield cultivars(HYV) (>50 d). Amylopectin accumulation was slower in LYV than in MYV and HYV during the earlier stage of kernel-filling, but the difference among them became smaller during the later stage. SS activity in LYV kernel was higher than that in MYV and HYV during 10–30 d after pollination, but decreased rapidly at 30 days later after pollination and had larger decreasing range than that in HYV. The peak of UGPase activity appeared on the 20th day after pollination in LYV, while on the 40th day after pollination in MYV and HYV, and the activity in LYV was obviously lower than that in MYV and HYV during the later stage of kernel-filling stage. The SBE activity during the later stage of kernel-filling (30–50 d after pollination) was HYV>MYV>LYV, and the decreasing range was 72.44%(LYV), 44.54%(MYV), and 30.21%(HYV). The activity of soluble starch synthase (SSS) in MYV and HYV showed “N” type curve changes with the first peak on the 30th day after pollination, while it showed single peak curve in LYV. The activity of ADPG pyrophosphorylase (ADPGPPase) in LYV was higher than that in MYV and HYV. The activity of starch debranching enzyme (DBE) in the three yield types of cultivar all decreased rapidly during the whole process of kernel-filling, and the difference among different types was not obvious.

Growth and Development Characteristics of Super-High-Yielding Mid-Season Indica Hybrid Rice

PAN Sheng-Gang, HUANG Qing-Ai, ZHANG Fan, QANG Jin-Ping, CAI Ming-Li, CAO Cou-Gui, TANG Xiang-Ru, LI Guo-Chi

Acta Agron Sin. 2011, 37(03):  537-544.  doi:10.3724/SP.J.1006.2011.00537

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 In order to study the characteristics of super high yielding (yield ≥ 12.0 t ha^-1) of mid-season indica hybrid rice cultivars in nutrition absorption, dry matter production and yield formation, we grew five rice cultivars (including lines), Yangliangyou 6, P88S/747, Luoyou 8, Luoyou 234 and Tianliangyou 2 in paddy fields. The leaf area index (LAI) at panicle initiation stage, heading stage and grain filling stage of super-high-yield rice was significantly higher than that of the high-yield rice (CK, Yangliangyou 6, grain yield ≥9.0 t ha^-1), which was in the range of 6.5–7.2, 8.5–8.9, and 6.5–7.0, respectively. The ratio of high effective leaf area to total leaf area at the heading stage was higher than that of CK, which was in the range of 60.0%–66.5%. Super high yielding rice had more dry matter accumulation than CK at the heading stage, grain filling stage and maturity stage, which was in the range of 13.5–15.0, 15.0–16.0, and 25.0–28.0 t ha^-1, respectively. Super-high-yield rice did not show any advantage in the absorption of N, P and K at mid-tillering stage compared with CK, however, had noticeable advantage in that at panicle initiation stage, heading stage and maturity stage. Furthermore, super high yield rice had more productive panicles, higher seed setting rate and grain weight in comparison with CK, which were in the range of 250×10⁴–290×10⁴ panicles per ha, 88.2%–92.3% and 29.0–31.0 g, respectively.

RESEARCH NOTES

Relationship between Seedling Traits and Yield Loss of Rapeseed Direct-Seeded in No-Tillage Rice Stubble Field

WANG Cui-Cui, CHEN Ai-Wu, LEI Hai-Xia, HAN Zi-Hang, LIU Fang, ZHOU Guang-Sheng, WU Jiang-Sheng, FU Ting-Dong

Acta Agron Sin. 2011, 37(03):  545-551.  doi:10.3724/SP.J.1006.2011.00545

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Technique ofdirect-seeding rape in no-tillage rice stubble field can decrease the labor and reduce the area of winter fallow fields, but its output is often less than the tillage cultivation model. In order to investigate the production constraints of direct-seeding rape in no-tillage field, we designed a pot experiment to determine physiological indexes of all lines such as root-shoot ratio, drought resistance, waterlogging tolerance and agronomy nitrogen use efficiency at seedling stage, and designed a field trial to determine the yield loss ratio of 15 lines in the no-tillage mode, then compared the relationship between physiological indexes at seedling stage and yield loss ratio in no-tillage mode. The result showed that, (1) differences in characters at mature period, yield and its components for the same rapeseed line in different cultivation modes depended on differentlines, (2) compared with that in the tillage mode，the lines that had small drop in shoot dry weight, economic coefficient or 1000-seed weight in no-tillage cultivation also had small yield loss ratio, (3) yield loss ratio at direct-seeding rape in no-tillage rice stubble field negatively correlated with root-shoot ratio, drought resistance and waterlogging tolerance at seedling stage, but positively correlated with nitrogen use efficiency at seedling stage, (4) the lines that had big root-shoot ratio, good drought resistance and waterlogging tolerance and robust seedling growth should be selected in the course of the cultivation and management, prevention against drought and waterlogging and balanced fertilization could improve production efficiency of direct-seeding rape in no-tillage rice stubble field.

New Restorer Lines and Genetic Analysis of Pingxiang Dominant Genic Male Sterile Rice

WANG Jian, YANG Xiao-Jie, FEI Qiang-Li, WANG Chun-Lian, LIU Pi-Qiang, ZHAO Kai-Jun

Acta Agron Sin. 2011, 37(03):  552-558.  doi:10.3724/SP.J.1006.2011.00552

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In construction of Pingxiang Dominant Genic Male Sterile Rice (PDGMSR) sterile gene mapping population, we found some reported maintainer lines shown the fertility restoration ability. Thus, this study systemly analyzed the fertility separation of F₁, F₂ and F₃ populations of the crosses between the PDGMSR and the reported maintainer lines. It was observed that the progenies from sib-crosses between male-sterile plant and fertile plant of the PDGMSR were always segregated in a ratio of 1 male-sterile to 1 fertile. The male-sterile plant could be fertile when kept in high temperature during the stage of young panicle development, and the selfed progenies gave a ratio of 3 male-sterile to 1 fertile. The progenies of F₁ from PDGMSR crossed with Gui 99, Teqing and 9311BB23 were complete fertile, indicating that Gui 99, Teqing and 9311BB23 have restoration ability. Harf of the F₂ populations derived from the F₁ plants of PDGMSRcrossed with Gui 99 or Teqing or 9311BB23 were complete fertile and the other half of the F₂ populations showed fertility segregating with the ratio of sterile plants to fertile plants of 3:13. Among the F₃ families derived from the fertile plants in the segregating F₂ populations, the ratio of the complete fertile F₃ families to the fertility-segregating F₃ families was 7:6. These results indicate that Gui 99, Teqing and 9311BB23 have restoring gene which shows dominant epistatic fertility restorer ability for PDGMSR and inhibits the expression of the dominant sterile gene in PDGMSR and consequently transfer the sterility to fertility.

Relationship of Dynamic Plant Height and Its Relative Growth Rate with Yield Using Recombinant Inbred Lines of Soybean

HUANG Zhong-Wen, WANG Wei, XU Xin-Juan, LI Jin-Ying, LU Wei-Guo

Acta Agron Sin. 2011, 37(03):  559-562.  doi:10.3724/SP.J.1006.2011.00559

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Selection for increasing yield potential is consistantlythe main goal of soybean breeding. Plant height influences yield with uncertainty in soybean. A population of 212recombinant inbred lines (RIL) was used to analyze the correlation of dynamic plant height and its relative growth rate with yield across two-year field experiments. The results were as followed. (1) The range of yield and plant height was 1 000–5 000 kg ha^–1, 38–128 cm respectively, which indicated the sample in the study had a good representativeness. Significant differences between plant height and its relative growth rate at the same developmental stages were observed among the RILs. (2) Yield was significantly and positively correlated with plant height at 20 days after emergence, and the correlation increased with the growing stages and the highest correlation occurred when plant height culminated. Yield was positively correlated with relative growth rate in plant height at earlier growth stages and negatively correlated at later stages, indicating that faster growth in plant height at later stage would not be beneficial to higher yield. (3) A negative exponential regression mode was observed in the relationship between yield and plant height. Yield increased steeply when plant height was less than 80 cm and this trend would slow down when plant height was over 80 cm. We found yields reached 4 000 kg ha^–1 when plant heights were 70–90 cm. The merits and demerits of phenotypic analysis using RIL and how to select plant height in soybean breeding were discussed.

Identification of 1BL·1RS Wheat-Rye Chromosome Translocations via 1RS Specific Molecular Markers and Genomic in situ Hybridization

YU Li, HE Fang, CHEN Gui-Ling, CUI Fa, QI Xiao-Lei, WANG Hong-Gang, LI Xing-Feng

Acta Agron Sin. 2011, 37(03):  563-569.  doi:10.3724/SP.J.1006.2011.00563

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Sixty-five rye-specific molecular markers were validated with two 1BL·1RS wheat-rye chromosome translocations (Kavkaz and Shannong 030-1), one 1AL·1RS wheat-rye chromosome translocation (Amigo), Jingzhouheimai, octoploid Triticale Jinsong 49, 1R-7R addition lines, Chinese Spring, Huixianhong, Mingxian 169, and Chancellor. Eleven markers were selected due to stable amplification, clear PCR products in electrophoresis gels, and good repeatability, of which eight markers, i.e., NOR-1, SECA2/SECA3, SCSS30.2, Sec1Gene, Sec1Pro, ω-Sec-P1/P2, ω-Sec-P3/P4, and IB-267 amplified specific bands associated with 1AL·1RS and 1BL·1RS translocations. Another three markers, O-SEC5′-A/O-SEC3′-R, IAG95-1, and SCM-9, were able to discriminate wheat–rye translocations involving different sources of 1RS. Both molecular markers and genomic in situ hybridization were used to detect the frequency of 1BL·1RS translocations in forty Shandong varieties (lines) bred in recent years. Among the forty varieties (lines), only 15% (Weimai 8, Lumai 14, Jining 13, Shannong 664, Shannongyoumai 3, and Yannong 25) harbored the 1BL·1RS translocation with the whole short arm of chromosome 1R of rye, and no 1AL·1RS or other translocation types were found.