Table of Content

12 August 2008, Volume 34 Issue 08

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

QTL Detection of Grain Size and Shape with BC₂F₂ Advanced Backcross Population of Rice (Oryza sativa L.)

CHEN Bing-Xu;SHI Ying-Yao;CUI Jin-Teng;QIAN Yi-Liang;LIU Hai-Yan;ZHANG Li-Ke;WANG Hui;GAO Yong-Ming;ZHU Ling-Hua;LI Zhi-Kang

Acta Agron Sin. 2008, 34(08):  1299-1307.  doi:10.3724/SP.J.1006.2008.01299

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The traditional mapping population with complicated genetic backbround is usually derived from a cross between two parents with a lot of unfavorable agronomic traits. The identified QTLs by traditional mapping can not be applied in genetic improvement of crops due to complicated interactions between QTLs and genetic background. The advanced backcross method for QTL mapping with elite variety as recurrent parent could partially eliminate the background effects and integrate QTL mapping with genetic breeding. In present study, using Shuhui 527, an elite indica restorer in China as recurrent parent and Milagrosa from Philippines as donor, the BC₂F₂ advanced backcross population with 199 individuals was developed. A total of 85 polymorphic SSR markers evenly distributed on 12 chromosomes were applied to genotype the mapping population. The grain length, grain width, ratio of grain length to width and thousand grain weight of the parents and the BC₂F₂ population were evaluated after har-vesting. The QTL identification of the above traits was conducted by one-way ANOVA (for single QTL) and two-way ANOVA (for digenic epistatic interaction loci). Among ten QTLs for grain length, grain width, ratio of grain length to width and thousand grain weight detected by one-way ANOVA (P<0.01), there were three pleiotropic QTLs. QTLs for ratio of grain length to width could be identified in QTLs for grain length due to highly close relationship between them. The results in present study indicated that qgl3b on chromosome 3 was a major QTL controlling grain length, ratio of grain length to width and thousand grain weight, which explained 29.37%, 26.15%, and 17.15% of phenotypic variation of the three traits and showed large additive effects (posi-tive allele from Shuhui 527) and negative overdominant effects, qgw8 was also a major QTL controlling grain width with 21.47% contribution to phenotypic variation and a minor QTL controlling thousand grain weight with 5.16% contribution to phenotypic variation. It had large additive effects (positive allele from Shuhui 527) and positive partial dominant effects in both traits. Two-way ANOVA (P<0.005) showed 61 pairs of digenic epistatic interactions involved in 54 QTLs among which 23 loci had pleiotropism affecting two to four traits and eight loci were the same as those detected by one-way ANOVA. It was observed that eight of thirteen pairs of digenic epistatic interactions related to ratio of grain length to width could be found in grain length. The results above will lay a good foundation in fine mapping, cloning and designed molecular breeding of favorable genes related to rice grain size and shape.

Combining Ability of Yield-Component Traits for Indica Chromosome Substituted Segments in Japonica Hybrids

YU Chuan-Yuan;JIANG Ling;XIAO Yin-Hui;ZHAI Hu-Qu;WAN Jian-Min

Acta Agron Sin. 2008, 34(08):  1308-1316.  doi:10.3724/SP.J.1006.2008.01308

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NC II(10´6) experiment derived from crossing between 10 indica-japonica chromosome segment substitution lines (CSSLs) with uniform japonica genome background and 6 japonica testers was conducted to analyze GCA, SCA, and relative genetic parameters of target chromosome segments. The GCAs of 10 CSSLs in main yield-component traits except 1000-grain weight were higher than those of background parent. CSSLs AIS84, AIS27, AIS3, AIS80, and AIS76 with chromosome substitution segments respectively from chromosomes 12, 4, 1, 11, and 11 ranked the top 5 in GCA of yield-related characters. The results indicated that heterosis of main yield-component traits in indica/japonica combinations at chromosome segment level was much stronger than that of typical japonica hybrid rice and intentionally substituting japonica chromosome segments with indica coun-terparts of X24-2–R367 (Chr. 12), R1854–R288 (Chr. 4), C970–C955 (Chr. 1), C1350–R257 (Chr. 11), and X52–R2913 (Chr. 11) could significantly upgrade yield potential of japonica hybrid rice. The SCA of different combinations with one same parent or different traits in the same combination had significant difference and the combinations with top SCA or bottom SCA could be derived from different parental GCA groups, which show that there is no causal relation between SCA and parental GCA. High GCA combining with strong SCA is a basic principle of parent selection in super-high yield hybrid rice breeding.

Heritability and Number of Genes Controlling Slow-Mildewing Resis-tance in Wheat Cultivar Lumai 21

NI Xiao-Wen;YAN Jun;CHEN Xin-Min;XIA Xian-Chun;HE Zhong-Hu;ZHANG Yong;WANG De-Sen;Morten Lillemo

Acta Agron Sin. 2008, 34(08):  1317-1322.  doi:10.3724/SP.J.1006.2008.01317

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It is very important to apply slow-mildewing resistance in wheat (Triticum aestivum L.) breeding, because slow-mildewing resistance is more durable than hypersensitive resistance. However, little information is available about the genetics of slow-mildewing resistance in Chinese wheat cultivars. Lumai 21 is identified as a slow-mildewing resistant wheat cultivar. To estimate the number of genes and its heritability, 200 lines of F_2:3 and F_2:4 populations derived from the cross between Lumai 21 and Jingshuang 16 (susceptible to mildew) and their parents were planted at Beijing and Anyang, Henan for disease evaluation in 2005–2007 growing seasons. The resistance was analyzed on the bases of both quantitative and qualitative genetic models. At least 4 resistance genes were detected in the 2 populations. The broad-sense heritability of the resistance was 0.53–0.78. Transgressive segregation result indicated that Jingshuang 16 might hold 1 minor gene for the resistance, and Lumai 21 involves at least 3 genes, accordingly.

Cloning and Expression of Transcription Factor TaMyb2s in Wheat

JIA Dong-Sheng;MAO Xin-Guo;JING Rui-Lian;ZHANG Xiao-Ke;CHANG Xiao-Ping

Acta Agron Sin. 2008, 34(08):  1323-1329.  doi:10.3724/SP.J.1006.2008.01323

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MYB, one of the biggest transcription factor families, plays a crucial role in regulating cellular morphogenesis, secondary metabolism, responding to hormone and stress signals in plants. Several MYB transcription factors were involved in response to various abiotic stresses, such as drought, salinity, and low temperature. In this study, Hanxuan 10, a wheat (Triticum aestivum) cultivar with strong drought resistance, was employed to clone MYB gene using specific primers of TaMyb2. Three types of cDNA with high identities of 95.3%, 95.0%, and 99.6% to TaMyb2 were obtained, and designated TaMyb2-I, TaMyb2-II, and TaMyb2-III, respectively. Structure analysis indicated that the 3 types of TaMyb2 gene contained 2 MYB DNA-binding domains, and classified to R2R3-MYB sub-family. Phylogenetic analysis based on the putative amino acid sequences indicated that TaMyb2 were closer to HvMYB4 and OsMYB4 originated from barley and rice, respectively, while had less relations to ZmMYB39 from maize (Zea mays), AtMYB15 from Arabidopsis and NtMYB1 from tobacco (Nicotiana tabacum). No corre-sponding relationships were observed between the TaMyb2s and A, B, D genomes of common wheat according to phylogenetic analysis of common wheat and its relative species T. urartu, Aegilops speltoides, Ae. tauschii, T. dicoccoides, and T. araraticum. The different expression patterns of TaMyb2s were observed using real-time quantitative PCR methods, though all the 3 types were associated with osmotic stress. TaMyb2-III was the most sensitive to hyperosmolality, followed by TaMyb2-I. In addition, the differential expression levels of TaMyb2s were detected in tender tissues at different developmental stages in wheat. The highest expression level of TaMyb2s was identified at seedling stage, especially in seedling roots, and then decreased gradually from seedling to heading stage. High expression levels of TaMyb2-I and TaMyb2-III only presented before jointing stage, while TaMyb2-II held about 2 folds till heading stage.

Genetic Diversity among Chinese Pea (Pisum sativum L.) Landraces Re-vealed by SSR Markers

ZONG Xu-Xiao;GUAN Jian-Ping;WANG Shu-Min;LIU Qing-Chang

Acta Agron Sin. 2008, 34(08):  1330-1338.  doi:10.3724/SP.J.1006.2008.01330

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A total of 1 221 pea (Pisum sativum L.) landraces from 19 provinces in spring sowing and winter sowing areas in China were employed for SSR analysis. One hundred and four polymorphic bands were detected by using 21 SSR primer pairs. 4.95 alleles were detected by each SSR primer pair on average, of which, 62.52% were effective alleles for diversity. SSR alleles were uniformly distributed in the landraces among provinces, while the number of effective alleles and Shannon’s information index (I) varied much among provincial based groups of genetic resources. Significant difference appeared in the majority of pairwise comparisons for genetic diversity between provincial based groups of genetic resources. Inner Mongolia possessed the highest level of genetic diversity (I = 1.066), followed by Gansu (I = 1.041), Sichuan (I = 1.026), Yunnan (I = 1.017) and Tibet (I = 0.996); Liaoning was the lowest (I = 0.515) in genetic diversity. Three gene pools were detected in Chinese pea landraces, which were polarized during its adaptation and cultivation in thousands years. Gene Pool I mainly consisted of the pea landraces from Inner Mongolia and Shaanxi provinces, Gene Pool II mainly consisted of the pea landraces from Henan province, and Gene Pool III mainly consisted of the pea landraces from other provinces except Shaanxi, Inner Mongolia and Henan. Pairwise Nei78 genetic distance among provincial based groups of pea landraces ranged from 5.159 to 27.586, 2 large cluster groups and 8 cluster sub-groups were identified based on the dendrogram interacting with the three gene pools. The clustering results of Chinese land-races reveal ecologically and geographically close correlation to their genetic diversity.

Association Analysis of Agronomic and Quality Traits with SSR Markers in Glycine max and Glycine soja in China: II. Exploration of Elite Alleles

WEN Zi-Xiang;ZHAO Tuan-Jie;ZHENG Yong-Zhan;LIU Shun-Hu;WANG Chun-E;WANG Fang;GAI Jun-Yi

Acta Agron Sin. 2008, 34(08):  1339-1349.  doi:10.3724/SP.J.1006.2008.01339

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On the basis of our previous results of SSR loci associated with the 16 traits, alleles of loci significantly associated with the traits were analyzed further in the present paper. The phenotypic allele effect was estimated through comparison between the average phenotypic value over accessions with the specific allele and that of accessions with “null allele”, and then the average positive (negative) allele effect (AAE) of a locus was calculated over the estimated phenotypic effects of all positive (negative) alleles. The results showed that a set of elite alleles, loci and their carrier materials were screened out. Among the elite alleles existed in Glycine max and Glycine soja, some were consistent, some inconsistent and some complementary. The phenotypic effects of posi-tive (negative) alleles were different from each other, and therefore, the average positive (negative) effects of a locus were also different from each other, indicating the potential of genetic recombination for breeding purposes. A same marker locus could associate with multiple traits with its alleles performed in their own way in direction and size, and the covariation of a same allele performed in two related traits might be the genetic basis of their phenotypic correlation. In summary, the results implied that association mapping could offer further genetic information complementary to the family-based linkage mapping for the im-provement of breeding procedures. In addition, further detailed information on elite alleles and phenotypic effects of the 16 traits were shown in the text.

QTL Mapping for Adult-Plant Resistance to Powdery Mildew, Lodging Resistance and Internode Length below Spike in Wheat

ZHANG Kun-Pu;ZHAO Liang;HAI Yan;CHEN Guang-Feng;TIAN Ji-Chun

Acta Agron Sin. 2008, 34(08):  1350-1357.  doi:10.3724/SP.J.1006.2008.01350

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Powdery mildew (Erysiphe graminis f. sp. tritici Em. Marchal.) and lodging cause great yield loss in wheat (Triticum aestivum L.) production. Adult-plant resistance (APR) is crucial in wheat breeding for permanent resistance to powdery mildew. Internode length below the spike (ILBS) is an important trait associated with lodging resistance (LDR) in wheat, however, the quantitative trait loci (QTLs) for ILBS have not been reported. In the present study, a set of 168 doubled haploid (DH) lines derived from the cross between Huapei 3 and Yumai 57 were used to detect QTLs associated with APR to powdery mildew, LDR, and ILBS with 305 SSR markers covering the whole wheat genome. The DH population and the parents were evaluated for APR to powdery mildew, LDR, and ILBS in 2005 and 2006 cropping seasons in Tai’an, Shandong province and in 2006 cropping season in Suzhou, Anhui province. QTL analyses were performed using the software of QTLNetwork version 2.0 based on the mixed linear model. A total of 12 additive QTLs and 10 pairs of epistatic QTLs were detected for APR to powdery mildew, LDR, and ILBS. One QTL qApr4D, donated by Yumai 57, was detected for APR to powdery mildew on chromosome 4D with increased resistance effect, accounting for 20.0% of the phenotypic variances without additive × environment (AE) interactions. Another QTL qIlbs7D for ILBS was identified on chromosome 7D, explaining 12.9% of the phenotypic variances without AE interactions. The results indicate both additive effects and epistatic effects are important genetic bases for APR to powdery mildew, LDR, and ILBS, which are also sometimes subjected to environmental modifications. The two QTLs, qApr4D and qIlbs7D, are useful for molecular marker–assisted selection in breeding for APR to powdery mildew and ILBS, respectively.

Cloning and Expression of Auxin-binding Proteins 1 Gene in Ramie [Boehmeria nivea (Linn.) Gaud.]

HUANG Yu;LIU Feng;GUO Qing-Quan;ZHANG Xue-Wen

Acta Agron Sin. 2008, 34(08):  1358-1365.  doi:10.3724/SP.J.1006.2008.01358

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Auxin, a kind of phytohormone discovered quite earlier, affects many processes of plant growth. If we identify the receptor interplaying with auxin directly and find out how the signal transfered into the tissue cells, it can help us to learn the mechanism of auxin effection, detecting many processes about plant’s growth deeply. ABP1 (auxin binding protein 1) was cloned from upland cotton (Gossypium hirsutum Linn.), capsicum, etc. But there is not any report about the auxin binding protein of ramie. In this paper the ABP1 cDNA core sequence was cloned by PCR with the primers designed using Boehmeria nivea(Linn.) Gaud as material. The identical molecules were cloned through 5’ and 3’ RACE and the whole sequence of the cDNA was cloned and sequenced which was a 849 bp molecule and could be translated into putative protein with 189 amino acids. BLAST analysis confirmed that this cDNA sequence shared a high homology with reported ABP gene of plants. It was designated as BnABP1 according to the auxin binding protein gene nomination habit and was submitted to GenBank with an accession number EU195804. In order to investigate the expression and regulation roles of BnABP1 in different tissues of ramie, the non-conservative sequence at 3’-end of BnABP1 was selected as target and its expression was detected by semi-quantitative RT-PCR with 18S rRNA as internal control. After running the PCR with various cycles the products electrophoresed in agarose gel and the integrating optic density (IOD) of bands was detected with gel analysis software. We take the ratio of IOD as relative ex-pressive quantity. The results indicated the expression of BnABP1 could be found in leaf, stem and bud but not in root in ramie. The expression level in bud, leaf and stem was with the relative content of 0.755, 0.632, and 0.360 respectively compared with that of 18S rRNA. Thus BnABP1 maybe expresses mostly in the tender tissues of plant.

Establishment of an Adzuki Bean (Vigna angularis) Core Collection Based on Geographical Distribution and Phenotypic Data in China

XU Ning;CHENG Xu-Zhen;WANG Su-Hua;WANG Li-Xia;ZHAO Dan

Acta Agron Sin. 2008, 34(08):  1366-1373.  doi:10.3724/SP.J.1006.2008.01366

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A total of 4 877 accessions of adzuki bean (Vigna angularis) are conserved in National Germplasm Conservation Center in China, but only a few of which have been used in adzuki bean improvement programme. Establishing a core collection of adzuki bean can simplify management and enhance utilization of genetic resources in adzuki bean research programmes. In this paper, Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA) was used to establish an adzuki bean core collection based on geographical distribution and phenotypic data. Finally, 8.92% of adzuki bean accessions were selected from entire collection as a core collection of 435 accessions sharing 98.3% phenotypes with the entire collection. The phenotypic correlations among different traits that may be under the control of co-adapted gene complexes were also preserved in the core collection. By different statistical methods such as comparison of mean using t-test, variance using F-test, phenotypic frequency distributions using χ²-test for the different traits, the core collection was validated to be a representative sample of the entire collection. This core collection will play an important role in the utilization of adzuki bean genetic resources.

In vitro Regeneration of Four Commercial Cotton (Gossypium hirsutum L.) Cultivars Grown in Xinjiang, China

CHEN Tian-Zi;WU Shen-Jie;LI Fei-Fei;GUO Wang-Zhen;ZHANG Tian-Zhen

Acta Agron Sin. 2008, 34(08):  1374-1380.  doi:10.3724/SP.J.1006.2008.01374

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Cotton grown in Xinjiang is critical to successful cotton production in China. Genetic improvement in cotton via biotechnology is limited due to lack of an efficient regeneration system. Here, an efficient somatic embryo procedure was developed to regenerate plantlets from hypocotyls of cotton cultivars Xinluzhong 20, Xinluzao 24, Xinluzao 33 and 03298 grown in Xinjiang. Calli were effectively produced on the medium with 0.01–0.10 mg L^-1 Kinetin (KT) and 0.10 mg L^-1 2,4-Dichlorophenoxyacetic acid (2,4-D), especially with 0.02 or 0.10 mg L^-1 KT and 0.10 mg L^-1 2,4-D. Split hypocotyl segments and double amounts of KNO₃ in the medium during induction of calli were beneficial to the emerge of embryogenic calli. Embryogenic calli and globular-stage somatic embryos were effectively initiated with high concentration of KT and low concentration of 2,4-D in ECM media (0.05 or 0.10 mg L^-1 KT and 0.01 mg L^-1 2,4-D). Embryos further developed into plantlets in MSBF medium under conditions of dehydration and ventilization achieved respectively by filter paper on medium and cotton tampon sealing flask. Using this proto-col, normal plantlets with strong roots well developed from these cotton cultivars for 6 to 8 months, increasing the range of cotton genotypes that can be regenerated. The successful regeneration protocol established in this study can be used to improve cotton cultivars by genetic engineering.

Microsatellite Markers for Culm Wall Thickness and Anatomical Features of Solid Stem Wheat 86-741

CHEN Hua-Hua; LI Jun;WAN Hong-Shen;WANG Ling-Ling;PENG Zheng-Song;YANG Wu-Yun

Acta Agron Sin. 2008, 34(08):  1381-1385.  doi:10.3724/SP.J.1006.2008.01381

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Lodging is a big problem in further increasing yield of wheat (Triticum aestivum L.). Development of variety with thickwall of basal internodes is an effective way to improve lodging resistance in wheat. A solid stem line “86-741” has been developed from the cross between hexaploid Triticale and common wheat, and acted as parent in lodging resistance breeding. To detect the gene(s) of culm wall thickness in 86-741, we made a cross between 86-741 and a stem hollow wheat line “Xinjiang Daomai” [Triticum petropavlovskyi Udacz. et Migusch] in 2004–2005 growth season, and developed its F₂ population in 2005–2006 growth season. The F₂ population was used for bulked segregation analysis (BSA) of the gene related to culm wall thickness by SSR markers. Anatomical analysis revealed that 86-741 had very smaller stem pith cavity with pith, thicker mechanical tissue and more vascular bundles than Xinjiang Daomai. The F₁ progeny of the cross showed some tendencies to its parent 86-741: culm with smaller diameters of pith cavity than the parent Xinjiang Daomai. The percentage of mechanical tissue in F₁ was smaller than that in 86-741, and the number of vascular bundles in F₁ was less than that in 86-741, but more than that in Xinjiang Daomai. Two recessive genes relating to pith and a single dominant gene on 3BL relating to culm wall thickness were detected in 86-741, respectively. The gene controlling culm wall thickness was temporarily designated as Cwt-1. We found 3 microsatellite (SSR) markers Xgwm-247, Xgwm-340, and Xgwm-547 linking to Cwt-1, in which Xgwm-247 was the closest to the gene with genetic distance of 5.3 cM. Our results indicated that Xgwm-247 can be used in marker-assisted selection (MAS) for lodging resistance breeding by selecting culm wall thickness trait in wheat.

Endopolyploidization Phenomenon of Chinese Cabbage (Brassica rapa ssp. pekinensis)

GUO Dong-Wei;LI Fei;MA Liu-Yin;LI Lian-Cheng;MA You-Zhi;SUN Ri-Fei

Acta Agron Sin. 2008, 34(08):  1386-1392. 

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The endopolyploidization is a universal phenomenon existing in the higher plant. The endopolyploidization, on which plant cells maintained a faster growth rate, is an important way of increasing copies of function genes which is necessary for plant to adapt its growing environment. The knowledge and research on the occurring and the feature of plant endopolyploidization phenomenon would be helpful for regulating efficiently differentiation of organs and accelerate the formation of valuable organs. In this paper, the Chinese cabbage and its relatives were used to determine the endopolyloidization level in tissues, organs, and leaves at different developmental stages with the technique of flow DNA analysis. The results showed that in Chinese cabbage the feature of endopolyploidization was also specific for tissues, developmental stages like in other plants reported previously. Some conducting tissues with higher lignification degree such as primary root, hypocotyls, stem and petiole demonstrated higher endo-polyploidization level than other nor-conducting tissues such as bract, cotyledon, laminae. In a given organ, the endopolyploidiza-tion level was raised in the progress of the organ development. When the organ was up to maturity its endopolypoidization level tended to be stable. The micros-graph revealed that the nuclei with different ploidies showed obvious difference in size and were scattered randomly into adjacent pellicle tissue cells of petiole of Chinese cabbage. The highest ploidy level of nuclei was 64C in leaves of Chinese cabbage, but 32C, 16C, and 16C in leaves of cabbage, mustard, and Arabidopsis thaliana, respectively, indicat-ing that the endopolyploidization level of the different plants in the same family is different.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Spatial and Temporal Variability of Available Nutrient in Cotton Field at Flower and Boll Stage and Its Effect on Lint Yield and Fiber Quality

YANG Zhi-Bin;CHEN Bing-Lin;ZHOU Zhi-Guo

Acta Agron Sin. 2008, 34(08):  1393-1402.  doi:10.3724/SP.J.1006.2008.01393

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Flower and boll stage is a key period for lint yield and fiber quality. Studying the spatial and temporal variability of available nutrient in cotton field at flower and boll stage can provide theoretical base for exploring the physiological measurements to improve lint yield and fiber quality. The field experiments were carried out in 2004 at application levels of 0, 120, 240, 360, and 480 kg N ha^-1(marked N0, N1, N2, N3, N4 respectively), 185 kg P ha^-1 and 118 kg K ha^-1 in Anyang and Nanjing, the typical representatives for ecological regions in Yellow River Valley and the middle lower reaches of Yangtze River Valley in China. The results indicated that, in the process of growth, the content of soil alkali-hydrolyzable nitrogen in 0–60 cm soil layers of N0 treatment presented the trend of decreasing firstly and increasing then. While that of other treatments decreased firstly, increased after topdressing, decreased again, and increased after the beginning of boll opening. Soil available phosphorus and available potassium in 0–60 cm soil layers at two experimental locations presented the similar trends of decreasing firstly and increasing then. Soil available nutrient in 0–60 cm soil layers decreased with the deepening of the layer. Soil alkali-hydrolyzable nitrogen and available phosphorus in the same soil layer of N1, N2, N3, and N4 treatments in Nanjing presented the similar decreasing as the horizontal distance to cotton plant increased, and in N0 treatment, there was no significant variation in alkali-hydrolyzable nitrogen and available phosphorus contents. The spatial and temporal variability for soil alkali-hydrolyzable nitrogen was more significant in Nanjing than in Anyang. While for soil available phosphorus, it was more significant in Anyang than in Nanjing. Soil available potassium in 0–60 cm soil layers in Nanjing and in 20–60 cm soil layers in Anyang presented the similar decreasing with the increasing of horizontal distance to cotton plant, while that in 0–20 cm soil layers in Anyang increasing. As a result, at the nitrogen application level of 360 kg ha^-1 for Anyang and 240 kg ha^-1 for Nanjing, yield components were the relatively optimal, yield was the maximum and the fiber quality of length and strength was better. So, in order to increase lint yield and fiber quality, different ecological regions should follow the spatial and temporal variability of soil available nutrient in cotton field at flower and boll stage to confirm the optimal fertilizer level.

Effects of Overexpression of Wheat Superoxide Dismutase (SOD) Genes on Salt Tolerant Capability in Tobacco

ZHANG Hai-Na;LI Xiao-Juan;LI Cun-Dong;XIAO Kai

Acta Agron Sin. 2008, 34(08):  1403-1408.  doi:10.3724/SP.J.1006.2008.01403

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For identification of the function of wheat novel superoxide dismutase (SOD) genes TaSOD1.1 and TaSOD1.2 in improving the salt tolerance, the transgenic tobacco plants with high expression levels of TaSOD1.1 and TaSOD1.2 were generated by the Agrobacterium tumerficians-mediated transformation approach. On NaCl treatment, the transgenic plants showed a better growth performance with less injured and more greenish leaves than control. The SOD activity was largely elevated in the tested transgenic tobacco plants than that in the control, so were the chlorophyll a, b contents, carotenoid content, soluble sugar content and soluble protein content. In the meantime, the MDA content was dramatically declined. Therefore, the transgenic tobacco plants with high expression levels of TaSOD1.1 and TaSOD1.2 could increase the SOD activity, alleviate the over-oxidation de-gree of cytoplasm membrane caused by NaCl stress, and enhance the NaCl tolerant capacity by the up-regulation of exotic target genes at the transcriptional level.

Effects of Nitrogen Application Amount on Characteristics of Nitrogen Utilization and Yield Formation in High Yielding Early Hybrid Rice

ZENG Yong-Jun;SHI Qing-Hua;PAN Xiao-Hua;HAN Tao

Acta Agron Sin. 2008, 34(08):  1409-1416.  doi:10.3724/SP.J.1006.2008.01409

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Two early season hybrid rice combinations, Luliangyou 996(two-line) and Jinyou 463(three-line) were used to study the characteristics of nitrogen utilization and yield formation under different N application amounts. The results showed that with the increasing of N amount the contents of chlorophyll in leaf and the nitrogen accumulation in stem, leaf, and spike increased, the leaf area index(LAI) enlarged and the dry matter accumulation before full heading especially from tillering to full heading pro-moted, the amount and the distribution rate of N accumulation in stem and leaf increased, but N dry matter production efficiency (NDMPE) and N production efficiency (NPE) decreased. The yields of the two rice combination were mainly affected by spikelets per panicle and the number of effective panicles. Optimum N rate increased the rate of the tillers with more than the critical stem-weight (a standard dry weight of stem used for judging whether the tiller grew into effective panicle or not) and the spikelets per panicle. But, the excessive N application decreased the rate of the tillers with more than the critical stem-weight and the spikelets per panicle, resulting in the decrease of dry matter production in late growing stages especially after milky ripe. Under the fertile soil condition in this study, optimum N amount was 225 kg per hectare for Luliangyou 996 which has large spike and compact plant and 180 kg per hectare for Jinyou 463 which has smaller spike, relax plant, and strong tillering ability.

Anatomical Structure and Chemical Features of Leaf in Brittle Mutant of Rice

WEI Cun-Xu;XIE Pei-Song;ZHOU Wei-Dong;CHEN Yi-Fang;YAN Chang-Jie

Acta Agron Sin. 2008, 34(08):  1417-1423.  doi:10.3724/SP.J.1006.2008.01417

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Plant mechanical strength is an important agronomic trait. A rice brittle mutant bc7(t) which derived from japonica variety Zhonghua 11 by radiation of ⁶⁰Co-g displayed normal phenotype similar to its wild type (WT) plants except for the fragi- lity of all plant body. To understand the mechanism of controlling plant mechanical strength, the anatomical structure and chemical features of leaf of brittle mutant bc7(t) were investigated. Anatomical analyses were carried out by means of various microscopic techniques, such as light microscopy, scanning electron microscopy and transmission electron microscopy. It was found that the cell walls of sclerenchyma cells of leaf sheath and leaf blade in the mutant were thinner than that in WT. For histochemical loca- lization of lignin, fresh freezing-cut transverse sections of leaf blade and sheath were stained with Wiesner reagents. Responding to the Wiesner reaction, the sclerenchyma cells below the epidermis, vascular bundle sheath and xylem were stained red. Though no noticeable staining difference in leaf blade between WT and mutant, the sclerenchyma cells of leaf sheath of mutant were stained slightly deeper than that of WT. Separation and purification of cell wall of leaf blade and sheath were carried out. The lignin content of cell wall was determined by thioglycollic acid method, the results revealed a slightly higher lignin content in mutant than in WT without significant difference. The cellulose content of cell wall was assayed with the anthrone reagent; the results showed that the amount of cellulose of leaf blade and sheath in mutant was significantly lower than that in WT. The test of silicon content of cell wall showed an increased content in the mutant. The energy dispersive X-ray micro-analysis attached to the FE-SEM provided the information on the distribution and content of silicon in the epidermal cells of leaf blade and sheath. The X-ray map analysis at the upper and lower epidermis of leaf blade and outer epidermis of leaf sheath showed that the content of silicon in mutant was obvious higher than that in WT. The result from silicon X-ray mapping of upper epidermis of leaf blade indicated that the distribution of silicon was concentrated in cell wall of silica cells. X-ray point analysis on the upper epidermis of leaf blade in the cell walls of silica cell, dork cell, long cell, and bulliform cell showed that the contents of silicon at these locations in mutant were all higher than these in WT. These results suggested that the reduction of cellulose might affect the formation of secondary cell walls, the thickness of cell wall and plant mechanical strength. Mutant might have a mechanism to balance the mechanical strength with an increase in silicon content.

Effects of Wheat-Residue Application and Site-Specific Nitrogen Manage- ment on Absorption and Utilization of Nitrogen, Phosphorus, and Potas-sium in Rice Plants

XU Guo-Wei;YANG Li-Nian;WANG Zhi-Qin;LIU Li-Jun;YANG Jian-Chang

Acta Agron Sin. 2008, 34(08):  1424-1434.  doi:10.3724/SP.J.1006.2008.01424

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More than half of wheat residues are burnt or discarded for years in China, which not only wastes organic fertilizer source, but also pollutes the environment. Meanwhile, heavy use of nitrogen fertilizer has become a serious problem in rice production, especially in Jiangsu province. The purposes of this study were to investigate the effects of wheat straw application and site-specific nitrogen management (SSNM) on the absorption and utilization of nitrogen (N), phosphorous (P), and potassium (K) in rice plants. A mid-season japonica rice cultivar of Yangjing 9538 was field-grown. Three treatments of farmers’ N-fertilizer practice (FFP), SSNM based on chlorophyll measurement (SPAD) readings, no nitrogen application, and with or without wheat residue application (the straw was incorporated to soil) were conducted. The results showed that wheat-residue incorporation re-duced N content and the accumulations of N, P, and K in plants at the early growth stage, increased P and K contents in plants during the whole growth period, and increased nitrogen use efficiency, harvest index, and biomass production efficiency of N, P, and K when compared with the straw removal treatment. Under the same amount of straw incorporation, SSNM reduced the amount of N and P absorption in plants, and increased transportation percentage of N, P, and K from heading to maturity and N and P harvest index. There was no significant difference in the amount of K absorption between SSNM and FFP. The results indi-cated that both wheat-residue application and SSNM can increase absorption and use efficiency of N, P, and K in rice plants.

Conditions and Indicators for Screening Cotton (Gossypium hirsutum) Genotypes Tolerant to Low-Potassium

TIAN Xiao-Li;WANG Gang-Wei;ZHU Rui;YANG Pei-Zhu;DUAN Liu-Sheng;LI Zhao-Hu

Acta Agron Sin. 2008, 34(08):  1434-1443.  doi:10.3724/SP.J.1006.2008.01435

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Commercial cotton production is currently limited by varying levels of potassium (K) deficiency. Screening for low-potassium tolerant cotton genotypes is necessary to alleviate the shortage of available potassium in soil. However, there is no standard procedure for such screening. Fifty cotton genotypes, mainly predominant cultivars/lines developed in 2004 in China, were tested under a hydroponic culture at low (0.02 mmol L^-1) and adequate (2.50 mmol L^-1) K levels. We determined genotypic differences in dry matter and associated traits at the seedling stage and compared with dry weight of reproductive organs (squares, flowers and uncracked and cracked bolls) in a field with potassium-deficient soil (59.88 mg kg^-1). Coefficient of variation (CV) among genotypes for whole plant dry weight increased from 15.13% at 1-leaf stage to 21.13% and 28.58% at 3- and 5-leaf stages, suggesting that differences among genotypes would manifest more clearly as seedlings aged. Together with the rather short grow-ing period (about 20 d), we considered the 5-leaf stage most suitable for the screening at the seedling stage. The relative dry weight (RDW) of the whole plant (0.02/2.50) correlated well (r = 0.7690, P < 0.01) with absolute dry weight (ADW) in the low K medium, but it had a higher CV than the latter (up to 37.39% at the 5-leaf stage). This suggests that the RDW would be a better screening index than ADW. Under the K-deficient media, highly significant positive correlations were observed between K ac-cumulation and dry matter (r = 0.9522), K utilization index (KUI, dry matter produced per 1‰ K) and dry matter (r = 0.9791), respectively. This shows that cotton tolerance to low K is a function of uptake and utilization. Correlation coefficients between root length and K accumulation, root surface area and K accumulation were 0.5201 (P < 0.01) and 0.3325 (P < 0.05), respectively. The ratio of spotted area caused by potassium deficiency to total cotyledon area (defined as S) was highly variable (CV = 44.46%) and normally distributed among genotypes, and inversely correlated with dry matter (r = –0.4455, P < 0.01). Thus the S value could be a secondary screening index for low K tolerance. The K content of seed did not affect the low-K tolerance of seedlings. We obtained a significantly positive correlation between dry matter at the seedling stage and dry weight of reproductive organs in the field (r = 0.5091, P < 0.01). Our conclusion is that preliminary screening of cotton genotypes tolerant to low-potassium at the seedling stage is feasible using a hydroponic culture. However, some important genotypes would need further screening in the field.

Relationship between Principle Alkaloid Contents in Natural and Purified Populations of Burley Tobacco

SHI Hong-Zhi;ZHAO Yong-Li;XIE Zi-Fa;CHEN Zhi-Hua;LIU Guo-Shun;WU Chun-Kui;LI Chao;LU Xi-Mei

Acta Agron Sin. 2008, 34(08):  1444-1449.  doi:10.3724/SP.J.1006.2008.01444

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In the natural population of burley tobacco, some plants have the ability converting nicotine to nornicotine due to gene mutation, resulting in the abnormal increase of nornicotine content, which has negative effect on tobacco safety and flavor quality. Burley tobacco hybrids Dabai 1 and Eyan 1 were used to investigate the relationship between principle alkaloid contents in bulk and individual samples from natural and purified populations. The results showed that in the purified populations nicotine content accounted for 92–95% of total alkaloid; the proportion of anatabine was higher than that of nornicotine, they were 3.2–5.0% and 1.6–2.8% respectively; the proportion of anabasine was the lowest. In the natural population contained large amount of converted plants, the nicotine content decreased and the nornicotine content increased, and the nornicotine content was higher than anatabine content. In the purified populations, as the increase of total alkaloids, all the principle individual alkaloids increased linearly, with the order of correlation coefficients with total alkaloids as nicotine > anatabine or anabasine > nornicotine, and with the order of slope for alkaloid increasing as nicotine > nornicotine > anatabine > anabasine. In natural populations, the correlation of total alkaloid with nicotine and nornicotine decreased, and that with anabasine and anatabine did not change. The nicotine and nornico-tine were positively correlated in purified populations, but negatively or not correlated in natural populations. Anatabine was sig-nificantly and positively correlated with anabasine in both populations.

Water Consumption Characteristic and Dry Matter Accumulation and Distribution in High-Yielding Wheat

ZHENG Cheng-Yan;YU Zhen-Wen;MA Xing-Hua;WANG Xi-Zhi;BAI Hong-Li

Acta Agron Sin. 2008, 34(08):  1450-1458.  doi:10.3724/SP.J.1006.2008.01450

Abstract ( 2295 )   PDF (729KB) ( 1748 )   Save

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Water resource deficiency is one of major problems in wheat (Triticum aestivum L.) production in North Plain of China. Irrigation plays an important role to obtain high grain yield and quality. Currently, many reports on the basis of different experiments and cultivars have suggested several irrigation regimes in wheat, but no consistent conclusion is available due to interactions between eco-environment and cultivar. In this study, two winter wheat cultivars were used under high-yielding cultivation in 2005–2007 growing seasons (with precipitations of 128.0 and 246.4 mm, respectively) to reveal the effects of irrigation amount on water consumption characteristics and dry matter accumulations in various organs. The results showed that the yield of treatment W2 (irrigated each 60 mm before sowing and at jointing) was the highest and the WUE of treatment W2 was significantly higher than that of other irrigation treatments in 2005–2006 and 2006–2007 wheat growing seasons. And when the precipitation was 246.4 mm from sowing to maturity in 2006–2007, the ratios of precipitation, irrigation amount and soil water amount to water consumption amount in treatment W2 were 47.32%, 23.04%, and 29.64%, respectively. Compared with in treatment W0, dry matter accumulation amount after anthesis and contribution of dry matter accumulation amount after anthesis to grains in irrigated treatments increased significantly with the highest of 8 241.59 kg ha^-1 and 84.18% respectively in W2. However over-irrigation significantly reduced the photosynthate and grain yield. Water consumption amount increased significantly with increasing irrigation amount, and the ratio of irrigation amount to water consumption amount increased too, but the ratio of precipitation to water consumption amount and the ratio of soil water amount to water consumption amount both decreased. The variation in the ratio of soil water amount to water consumption was larger than others. As far as grain yield, WUE and WUE of irrigation concerned in the experiment, the most appropriate treatment for recommendation was treatment W2, which was irrigated 60 mm before sowing and at jointing stage respectively. The ratio of soil water amount to water consumption amount and the WUE of irrigation were higher in treatment W1 than in treatment W2, and the grain yield in treatment W1 was 8 797.73 kg ha^-1 when the precipitation was 246.4 mm. The results can offer a useful reference for formulating water-saving cultivation techniques in the areas with different water resources.

Effects of Source/Sink Ratio on Boll Weight and Physiological Activities of Leaves at Middle and Lower Fruiting Branches in Cotton

SUN Hong-Chun;LI Cun-Dong;ZHANG Yue-Chen;LU Wen-Jing

Acta Agron Sin. 2008, 34(08):  1459-1463.  doi:10.3724/SP.J.1006.2008.01459

Abstract ( 1787 )   PDF (484KB) ( 1158 )   Save

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Cotton is one of important cash crops, but so far, few studies on the boll and leaf system at the same node position in cotton were reported. In this study, the effects of source/sink ratio on growth and development and physiological characteristics in cotton were evaluated using CCRI29, a BT-transgenic hybrid cotton cultivar. Three treatments were designed in the experiment: picking off buds on the fruit branch at 8 d after anthesis for leaving two or three leaves to support one boll (PB), picking off some leaves on the fruit branch at 8 d after anthesis for leaving one leaf to support two bolls (PL), and normal training managements (CK). The results indicated that in PB treatment, the content of soluble protein increased and the chlorophyll content in the later growth stage boosted in middle and lower fruit branch leaves, prolonging the function period of the leaves. In PL treatment, the chlorophyll content of leaves was promoted in the earlier growth stage, and decreased sharply in the later growth stage, and the soluble protein content of leaves was the lowest among the three treatments, suggesting that there was a temporarily physiological compensation effect in fruit branch leaves, but the leaf senescence was accelerated by cutting leaves at late growth stage. Altered the ratio of source/sink also affected the SOD and POD activities and MDA content in fruit branch leaves, showing a tendency that both increasing and decreasing source/sink ratio could reduce the activities of SOD and POD. The MDA content of leaf under different treatments was ranked as PL>CK>PB. The results of statistic analysis indicated that there were a significant, positive correlation between SOD activity and POD activity ( r = 0.845**, P < 0.01) in CK treatment, but no correlation between SOD and POD activities after changing the source/sink ratio, indicating that the ratio of source/sink affected the physiological characteristics and function period of fruit branch leaves in cotton. As a result of changing source/sink ratio, the ringle boll weigh was PB>CK>PL.

Effect of Patterns of Straw Returning to Field on Contents of Available N, K in Soil and the Later Rice Growth

XIAO Xiao-Ping;TANG Hai-Tao;JI Xiong-Hui

Acta Agron Sin. 2008, 34(08):  1464-1469.  doi:10.3724/SP.J.1006.2008.01464

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The contents of available N, K in the different growth stages of later-rice under different patterns of straw returning to field (SRF) were tested respectively in the experiment. The results indicated that the patterns of SRF siginificantly influenced the contents of NH₄⁺-N in soil and unconspicuously influenced the available K contents of soil and NO₃^--N content of soil. The content of available NH₄⁺-N under conventional tillage with high stubble (CTHS) was 40.8% and 36.7% higher than that under zero tillage with high stubble (ZTHS) and that under zero tillage with covering straw (ZTC), respectively. The available K content of soil under CTHS was 7.5% and 2.0% higher than that under ZTHS and that under ZTC, respectively. CTHS could improve rice growth, increase the content of chlorophyll, make full use of light energy, and enhance photosynthetic rate. The yield of CTHS was 5.8% and 9.0% higher than that of ZTHS and that of ZTC, respectively. So in conclusion, CTHS is the optimal pattern for local area.

Effects of Shading in Field on Key Enzymes Involved in Starch Synthesis of Summer Maize

ZHANG Ji-Wang;DONG Shu-Ting;WANG Kong-Jun;HU Chang-Hao;LIU Peng

Acta Agron Sin. 2008, 34(08):  1470-1474.  doi:10.3724/SP.J.1006.2008.01470

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The shading experiment was conducted in the field in 2004–2005, using the maize cultivar ND108, to study the effects of shading at different stages on key enzymes involved in starch synthesis of maize, and provide theoretical evidence to improve yield and quality of summer maize. The field was shaded by shading nets which prevented 50% sunlight. The heights of the nets were raised with the growth of maize plant, and the distance between the nets and the top of maize plant remained about 2.5 m. Only the illumination condition was changed after shading, while the aeration condition and relative humidity were not changed. Other environmental factor changes were due to the change of illumination intensity. The treatments were designed at seedling to jointing, jointing to flowering, and flowering to maturity stages, with 24, 28, and 48 days shading respectively. The activities of SPS (sucrose-phosphate synthase), SS (sucrose synthase), SSS (soluble starch synthase), GBSS (granule-bound-starch synthase), ADPGPPase (adenosine diphosphorate glucose pyrphorylase), and UDPGPPase (uridine diphosphorate glucose pyrophorylase) were determined every 10 days after shading, and kernel yield was measured after maturity stage. The results showed that the biomass and kernel yield of ND108 decreased significantly after shading. Compared with the control (nature sunlight without shading), the biomass of ND108 decreased by 23.9%, 31.4%, and 38.9% from seedling to jointing, jointing to flowering, and flowering to maturity stages, respectively, while the kernel yield decreased by 24.6%, 35.6%, and 68.2%, respectively. Leaf SPS activity and kernel SS, GBSS, SSS, ADPGPPase, and UDPGPPase activities of maize decreased significantly after shading, and different shading phases had different effects with the sequence of flowering to maturity > joining to flowering > seedling to join-ing. The results suggested that the main causes of grain yield and starch content decreasing after shaded were the decreasing of both photosynthesis and starch synthesis key enzyme activities which caused the decreasing of the transportation and distribution of photosynthate from leaf to grain.

RESEARCH NOTES

Isolation and Regulative Region Analysis of Promoter of Stress-Related Gene GmDREB3 from Soybean

SUN Xiao;DONG Jian-Hu;CHEN Ming;XU Zhao-Shi;YE Xing-Guo;LI Lian-Cheng;QU Yan-Ying;MA You-Zhi

Acta Agron Sin. 2008, 34(08):  1475-1479.  doi:10.3724/SP.J.1006.2008.01475

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In order to analyze transcriptional regulative mechanism of GmDREB3 gene, the GmDREB3 promoter (1 648 bp) was isolated from soybean genome using SiteFinding-PCR method. The sequences is abundant in A/T base and predicted to contain a lot of putative cis-element, such as low-temperature responsive element (MYC), dehydration responsive element (MYB), ABA responsive element (ABRE), and so on, as well as TATA-box in biological database. To identify the key promoter regulative re-gion controlling gene expression, GmDREB3 promoter was truncated according to the prediction of putative cis-element and in-serted into the site upstream of GUS reporter gene. Then, vectors containing different length GmDREB3 promoters were trans-ferred into wheat callus by particle bombardment, and after different stress treatments, function of these putative cis-elements was analyzed by identifying activation of GUS using histochemistry staining and GUS fluorescence intensity analysis. The results indicated that the promoters between –285 and –1 648 bp (relative to the translational start site) activated expression of GUS re-port gene under drought and low temperature stresses. But only the promoter region between –285 and –1 117 bp could activate expression of maximal GUS gene in wheat callus. Another promoter region between –1 117 and –1 464 bp weakened the ability for activating expression of GUS gene under drought and low-temperature stress conditions. Thus, it was suggested that there are some positive regulating motif between –285 and –1 117 bp and negative regulating motif between –1 117 and –1 464 bp of GmDREB3 promoter. As a result, the expression of GmDREB3 gene can be kept in an appropriate level response to various stresses through the regulation of both positive and negative regulating motifs.

Application of ISSR in Genetic Relationship Analysis of Sorghum Species

FANG Xue-En;CHEN Qin;YIN Li-Ping;WANG Wei

Acta Agron Sin. 2008, 34(08):  1480-1483.  doi:10.3724/SP.J.1006.2008.01480

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The genetic relationship among six sorghum species, namely, S. bicolor, S. bicolor×S. sudanese, S. saccharatum, S. sudanese, S. almum, and S. halepense was analyzed by inter-simple sequence repeat (ISSR) method. The results showed that the diversity of sorghum was high at DNA level. Twenty-two primers selected from 110 ISSR primers could amplify 182 clear and reproducible bands, of which 153 bands were polymorphic, accounting for 84.0%. All the sorghum species studied could be distinctly divided into two major groups with the genetic distance level at 0.25 by cluster analysis based on the Neighbor-Joining method. Some primers produced highly polymorphic band patterns in different species, such as IR 89, IS16, according to them, all the sorghum species used could be identified. The results could be used in classification、identification and evolution of sorghum.

Genetic Diversity and Quality Difference of Systemic Selective Lines in Ningmai 13

ZHANG Ping-Ping;MA Qing;QIAN Cun-Ming;MA Hong-Xiang

Acta Agron Sin. 2008, 34(08):  1484-1488.  doi:10.3724/SP.J.1006.2008.01484

Abstract ( 1958 )   PDF (565KB) ( 1159 )   Save

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Systemic selection is an effective method for wheat (Triticum aestivum L.) breeding. A set of 25 SSR primers located on 21 wheat chromosomes were used to investigate the genetic diversity of 65 lines derived from Ningmai 13. Simpson diversity index (Hi) ranged from 0 to 0.57 with an average of 0.08 per primer, which is a powerful evidence for systemic selection. Only 9 out of 25 were polymorphic primers. Nine lines originated from Ningmai 13 characterized with Pina-D1a/Pinb-D1b, and Pinb-D1b might come from natural cross. Horniness was significantly affected by environments, and horniness and hardness gene detection should be used in kernel quality selection together. Systemic selection should be useful for agriculture and quality character improvement.