基于DUS测试的水稻标准品种形态性状多样性分析

对水稻DUS测试标准品种进行多样性评价,为DUS测试标准品种的选择和优化提供依据。以DUS测试指南中规定的49个水稻标准品种为材料,根据2008年在杭州田间试验对59个形态性状的调查数据,利用PopGen32软件计算了等位变异数、有效等位变异数和Shannon's多样性信息指数,对标准品种的形态性状多样性进行了评价;并根据其多样性参数采用NTSYS软件对标准品种进行了聚类分析。结果表明,59个形态性状在19份籼稻和30份粳稻品种中分别检测到201和262个等位变异,平均每个性状可以检测到3.4068（籼稻）和4.4407(粳稻)个等位变异,籼、粳稻类群中59个性状的平均Shannon's多样性指数分别为0.8318（0~1.7674）和0.9828（0~1.8547）。聚类分析结果表明,籼、粳稻群体内品种间的形态性状相似系数分别介于0.45~0.81和0.36~0.76,取相似系数0.70为阈值,可将19份籼稻和30份粳稻品种分别分为16和27类。多样性分析表明本研究的49个品种形态性状多样性丰富,具有标准品种性状描述的示例和校正作用;根据聚类分析结果,可将现有标准品种的数量减少至43个。本研究为水稻新品种DUS测试中标准品种的选择和优化提供了参考依据,同时也可供研制其他植物的DUS测试标准借鉴。     

糯玉米种质品质性状鉴定和SSR标记遗传多样性分析

对165份来源不同的糯玉米农家种和自交系的穗粒性状和淀粉品质性状进行了鉴定,并利用60对SSR标记进行了遗传多样性分析。结果表明,165份糯玉米种质穗长、秃顶长、行数、行粒数和穗粗变异较大,粗淀粉含量、支链淀粉含量和淀粉糊化特性RVA特征谱带值各指标变异丰富。60 对SSR引物在165份材料间共检测到281个等位基因变异,PCR扩增片段大小介于90～690bp,每对引物检测到2～9个等位基因,平均为4.68个;每对SSR 引物的多态信息量( PIC) 在0.332～0. 860之间,平均为0. 690。利用UPGMA 聚类分析方法将供试种质自交系分为3类,划分结果基本符合品系的来源情况,生产应用的多数糯玉米自交系材料与我国西南地区糯玉米地方品种材料具有较远的亲缘关系。显示出165份糯玉米种质具有丰富的遗传多样性,可为糯玉米杂优利用和遗传改良提供遗传基础。     

玉米种质资源的抗倒伏性评价及鉴定指标筛选

倒伏是影响玉米高产稳产的主要问题之一。本研究以181份玉米自交系为试验材料,对22个与抗倒伏性紧密相关的性状进行测定,采用相关性分析、主成分分析、聚类分析、逐步判别分析和岭回归分析等方法,综合评价玉米自交系的抗倒伏性。相关性分析的结果表明,22个性状间存在不同程度的相关性。主成分分析的结果表明,前7个主成分代表了181份玉米自交系的22个性状74.460%的信息,其贡献率分别为25.700%、12.369%、9.782%、8.159%、7.782%、5.490%和5.177%。聚类分析的结果表明,当遗传距离为3.5时,181份玉米自交系被聚为4大类,第Ⅰ类群有35份自交系、第Ⅱ类群有47份自交系、第Ⅲ类群有49份自交系、第Ⅳ类群有50份自交系。逐步判别分析的结果表明,175份玉米自交系被正确判别,判对概率为96.69%;6份玉米自交系被误判,误判率为3.31%,这说明聚类分析的结果是准确可靠的。进一步利用岭回归方法筛选出半纤维素含量、穿刺强度、第3节间长度、第3节间直径、穗位高和维管束总面积6个性状,建立了可靠的玉米自交系抗倒伏性评价回归模型。在181份玉米自交系中,以AHU24、e220、7026B等35份自交系的抗倒伏能力最强。本研究结果为玉米抗倒伏种质资源的遗传改良和组配抗倒伏杂交种提供借鉴。     

六出花属DUS测试性状筛选与评价

以39份六出花品种为试材,对51个候选性状进行观测,比对不同测量方式对花相关数量性状的影响,并同时研究了同品种中外花被片与侧外花被片长度的相关性。结果表明:"花序:花序梗长度"和"花:花梗长度"不满足DUS测试性状要求,最后筛选出43个性状作为DUS测试性状。12个数量性状可分别划分为3~7级;不同观测方式对花相关数量性状具有影响,推荐DUS测试时采用随机观测方式;不同批次的同一品种观测结果部分性状上存在差异;多数品种的中外花被片长度与侧外花被片长度之间呈线性正相关;形态性状的聚类分析结果支持将"花:主色"作为分组性状。     

玉米自交系秸秆品质性状鉴定与评价

利用近红外漫反射光谱法,对50份常用普通玉米自交系和50份高油自交系秸秆的中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、可溶性糖(WSC)和粗蛋白(CP)4个品质性状进行了鉴定评价和相关性分析。结果表明,各品质性状变异较大,各性状自交系间差异均达极显著水平。不同品质性状变异程度不同,其中WSC含量变异最大,变异系数达34.23%。WSC与NDF、ADF极显著负相关,NDF与ADF含量极显著正相关。高油系表现为高WSC、CP和低NDF、ADF含量,总体上高油系秸秆品质优于普通玉米。     

中国温带糯玉米自交系遗传及品质性状分析

利用SSR标记研究了40份中国温带常用糯玉米自交系的遗传变异,用32对扩增带型稳定的引物,从供试材料中检测出152个等位基因变异,每对引物检测等位基因2～9个,平均4.75个,平均多态信息量0.632;遗传多样性和聚类分析把40份供试糯玉米自交系分为4个类群;对40份糯玉米自交系籽粒的蛋白质、可溶性糖、还原糖、淀粉和赖氨酸含量进行测定,结果表明,糯玉米籽粒营养成分中蛋白质与淀粉之间存在消长关系,可溶性糖与还原糖含量之间存在显著正相关,且随着蛋白质含量的增加,与营养品质密切有关的赖氨酸含量随之增加.     

基于表型性状的玉米特异性测试近似品种筛选方法

特异性、一致性和稳定性是植物品种权授权、品种审定、登记的基本条件。近似品种选择是特异性测试的技术关键。本研究依据玉米DUS测试指南,对黄淮海地区3696份玉米品种进行了多年同一测试地点的性状观测,构建了黄淮海地区玉米品种测试性状数据库。通过对不同测试性状表达状态代码波动范围的研究,将玉米测试性状根据表达稳定性分为4级,确定了玉米品种27个测试性状表达状态代码的波动范围。在上述工作基础上,建立了基于测试性状表型数据库的近似品种筛选方法,提高了近似品种筛选的严谨性和效率。     

基于DUS测试的上海粳稻地方品种遗传多样性分析

利用水稻DUS测试指南(2012版)中的38个水稻标准品种和52个基本测试性状对上海地区的172个粳稻地方品种进行遗传多样性分析,并与14个上海地区选育的申请品种保护的粳稻品种作比较。结果表明:地方品种表型性状共检测到176个等位变异,平均每个测试性状检测到3.6667个,变幅介于1~8个。Shannon's多样性指数(H')平均值为0.6834,变幅介于0~1.9327,77.08%的性状存在3个及以上的等位变异;地方品种的等位变异数、每个性状的等位变异数及其变异幅度、多样性指数平均值等均大于现代育成品种,在外观形态上,地方品种的遗传多样性比现代育成品种更丰富。利用UPGMA法进行聚类分析发现在相似系数为0.53时,可将186个粳稻品种分为3个类(亚)群,现代育成品种单独组成一个亚群;而主坐标分析将186个粳稻品种明显的分为地方品种和现代育成品种两大区。地方品种具有丰富的多样性,与现代育成品种具有明显的形态差异,可为今后粳稻育成品种的改良提供更多的形态基础。     

无髯鸢尾新品种DUS测试性状筛选

植物新品种特异性、一致性和稳定性(DUS)测试是新品种保护的基础和依据,测试性状的筛选是DUS测试的核心。为制定无髯鸢尾DUS测试指南,初步确定测试性状43个,结合性状间R型聚类分析性状间相关性,去除相关性大、贡献较小的雌蕊长、叶长性状,最终确定操作性强、区别明显的测试性状41个;利用品种间Q型聚类分析确定测试指南的分组性状4个;对性状进行分级及分布分析,保证无髯鸢尾测试指南的可行性,为无髯鸢尾品种测试与授权提供技术支持。     

山羊豆种质资源形态多样性分析

采用15个形态性状对43份山羊豆种质资源进行遗传多样性分析,结果表明,山羊豆种质资源遗传变异丰富,多样性指数为1．863,其中俄罗斯南部地区可能是山羊豆形态多样性的分布中心。基于形态性状的聚类分析把43份材料聚为5类,其中第1类15份资源的株高和主茎分枝数明显高于其他类,且叶量丰富,营养性状表现良好;结实性状中荚果长和百粒重较大,综合性状表现较好,可以从中筛选合适的材料作为引种驯化和育种的试验材料。     

Analysis of genetic diversity and relationships among waxy maize inbred lines in Korea using SSR markers

Information regarding the genetic diversity and genetic relationships among elite inbred lines is necessary to improve new cultivars in maize breeding programs. In this study, genetic diversity and genetic relationships were investigated among 84 waxy maize inbred lines using 50 SSR markers. A total of 269 alleles were identified at all the loci with an average of 5.38 and a range between 2 and 13 alleles per locus. The gene diversity values varied from 0.383 to 0.923 with an average of 0.641. The cluster tree generated using the described SSR markers recognized two major groups at 32% genetic similarity. Group I included 33 inbred lines while group II included 51 inbred lines. The clustering patterns of most of the waxy maize inbred lines did not clearly agree with their source, pedigree or geographic location. The average GS among all inbred lines was 35.7 ± 10.8. Analysis of waxy maize inbred lines collected from Korea and China at 50 SSR loci revealed higher values of average number of alleles (4.9) and gene diversity (0.638) in Korean inbred lines as compared to Chinese inbred lines (3.5 and 0.563, respectively). The information obtained from the present studies would be very useful for maize breeding programs in Korea.     

Analysis of genetic distance by SSR in waxy maize

We examined the genetic diversity of 80 inbred waxy maize lines using 22 SSR molecular markers that could be used to achieve heterosis in waxy maize. Eighty inbred waxy maize lines with different phenotypes, 40 yellow, 25 white, 13 black, and two red lines were analyzed by SSR molecular marker fingerprint and cluster analysis. Using a standard genetic distance of 0.55, the 80 waxy maize inbred lines were clustered into nine groups. Among them, group II, group V, groups VII and VIII, and group IX were divided into three subgroups at a genetic distance of 0.46, into two subgroups at 0.49, into two subgroups at 0.46, and into four subgroups at 0.493, respectively. All but one of the yellow waxy maize inbred lines were clustered in groups VI, VII, VIII, and IX. Group IX (30 lines) contained 28 yellow lines; the other 11 yellow lines were distributed among groups VI, VII and VIII. Among the 25 white lines, 21 were clustered in groups III, V, VI and the third subgroup of group II. The black line N72 was in a group of its own. The black lines N75, N76 and N78 were distributed in groups VII, VIII and IX, respectively. The other nine black lines were clustered in group II. The red lines were distributed in the second subgroup of group II and there was no difference in genetic distance between them. In conclusion, there were considerable genetic differences among waxy maize inbred lines of different colors. The mean genetic distance of inbred lines of the same color was significantly less than that of lines of different colors. Therefore, we concluded that it was more accurate to determine the difference between the populations using the highly stable DNA genetic markers.     

Identification of Genetic Differentiation between Waxy and Common Maize by SNP Genotyping

Waxy maize (Zea mays L. var. ceratina) is an important vegetable and economic crop that is thought to have originated from cultivated flint maize and most recently underwent divergence from common maize. In this study, a total of 110 waxy and 110 common maize inbred lines were genotyped with 3072 SNPs to evaluate the genetic diversity, population structure, and linkage disequilibrium decay as well as identify putative loci that are under positive selection. The results revealed abundant genetic diversity in the studied panel and that genetic diversity was much higher in common than in waxy maize germplasms. Principal coordinate analysis and neighbor-joining cluster analysis consistently classified the 220 accessions into two major groups and a mixed group with mixed ancestry. Subpopulation structure in both waxy and common maize sets were associated with the germplasm origin and corresponding heterotic groups. The LD decay distance (1500–2000 kb) in waxy maize was lower than that in common maize. Fourteen candidate loci were identified as under positive selection between waxy and common maize at the 99% confidence level. The information from this study can assist waxy maize breeders by enhancing parental line selection and breeding program design.     

Identification of functional genetic variations underlying drought tolerance in maize using SNP markers

Single nucleotide polymorphism (SNP) is a common form of genetic variation and popularly exists in maize genome. An Illumina GoldenGate assay with 1 536 SNP markers was used to genotype maize inbred lines and identified the functional genetic variations underlying drought tolerance by association analysis. Across 80 lines, 1 006 polymorphic SNPs (65.5% of the total) in the assay with good call quality were used to estimate the pattern of genetic diversity, population structure, and familial relatedness. The analysis showed the best number of fixed subgroups was six, which was consistent with their original sources and results using only simple sequence repeat markers. Pairwise linkage disequilibrium (LD) and association mapping with phenotypic traits investigated under water-stressed and well-watered regimes showed rapid LD decline within 100-500 kb along the physical distance of each chromosome, and that 29 SNPs were associated with at least two phenotypic traits in one or more environments, which were related to drought-tolerant or drought-responsive genes. These drought-tolerant SNPs could be converted into functional markers and then used for maize improvement by marker-assisted selection.     

Genetic Diversity and Molecular Evolution of Chinese Waxy Maize Germplasm

Waxy maize (Zea mays L. var. certaina Kulesh), with many excellent characters in terms of starch composition and economic value, has grown in China for a long history and its production has increased dramatically in recent decades. However, the evolution and origin of waxy maize still remains unclear. We studied the genetic diversity of Chinese waxy maize including typical landraces and inbred lines by SSR analysis and the results showed a wide genetic diversity in the Chinese waxy maize germplasm. We analyzed the origin and evolution of waxy maize by sequencing 108 samples, and downloading 52 sequences from GenBank for the waxy locus in a number of accessions from genus Zea. A sharp reduction of nucleotide diversity and significant neutrality tests (Tajima’s D and Fu and Li’s F*) were observed at the waxy locus in Chinese waxy maize but not in nonglutinous maize. Phylogenetic analysis indicated that Chinese waxy maize originated from the cultivated flint maize and most of the modern waxy maize inbred lines showed a distinct independent origin and evolution process compared with the germplasm from Southwest China. The results indicated that an agronomic trait can be quickly improved to meet production demand by selection.     

Maize association population: a high-resolution platform for quantitative trait locus dissection

Crop improvement and the dissection of complex genetic traits require germplasm diversity. Although this necessary phenotypic variability exists in diverse maize, most research is conducted using a small subset of inbred lines. An association population of 302 lines is now available--a valuable research tool that captures a large proportion of the alleles in cultivated maize. Provided that appropriate statistical models correcting for population structure are included, this tool can be used in association analyses to provide high-resolution evaluation of multiple alleles. This study describes the population structure of the 302 lines, and investigates the relationship between population structure and various measures of phenotypic and breeding value. On average, our estimates of population structure account for 9.3% of phenotypic variation, roughly equivalent to a major quantitative trait locus (QTL), with a high of 35%. Inclusion of population structure in association models is critical to meaningful analyses. This new association population has the potential to identify QTL with small effects, which will aid in dissecting complex traits and in planning future projects to exploit the rich diversity present in maize.     

The relationship between parental genetic or phenotypic divergence and progeny variation in the maize nested association mapping population

Appropriate selection of parents for the development of mapping populations is pivotal to maximizing the power of quantitative trait loci detection. Trait genotypic variation within a family is indicative of the family's informativeness for genetic studies. Accurate prediction of the most useful parental combinations within a species would help guide quantitative genetics studies. We tested the reliability of genotypic and phenotypic distance estimators between pairs of maize inbred lines to predict genotypic variation for quantitative traits within families derived from biparental crosses. We developed 25 families composed of ~200 random recombinant inbred lines each from crosses between a common reference parent inbred, B73, and 25 diverse maize inbreds. Parents and families were evaluated for 19 quantitative traits across up to 11 environments. Genetic distances (GDs) among parents were estimated with 44 simple sequence repeat and 2303 single-nucleotide polymorphism markers. GDs among parents had no predictive value for progeny variation, which is most likely due to the choice of neutral markers. In contrast, we observed for about half of the traits measured a positive correlation between phenotypic parental distances and within-family genetic variance estimates. Consequently, the choice of promising segregating populations can be based on selecting phenotypically diverse parents. These results are congruent with models of genetic architecture that posit numerous genes affecting quantitative traits, each segregating for allelic series, with dispersal of allelic effects across diverse genetic material. This architecture, common to many quantitative traits in maize, limits the predictive value of parental genotypic or phenotypic values on progeny variance.     

Identification of kernel iron- and zinc-rich maize inbreds and analysis of genetic diversity using microsatellite markers

Development of micronutrient enriched staple foods is an important breeding goal in view of the extensive problem of ‘hidden hunger’ caused by micronutrient malnutrition. In the present study, kernel iron (Fe) and zinc (Zn) concentrations were evaluated in a set of 31 diverse maize inbred lines in three trials at two locations – Delhi (Kharif 2007 & 2008) and Hyderabad (Rabi 2007–08). The ranges of kernel Fe and Zn concentrations were 13.95–39.31 mg/kg and 21.85–40.91 mg/kg, respectively, across the three environments. Pooled analysis revealed significant genotype × environment (G × E) interaction in the expression of both the micronutrient traits, although kernel Fe was found to be more sensitive to G × E as compared to kernel Zn. Seven inbred lines, viz., BAJIM-06-03, DQPM-6, CM212, BAJIM-06-12, DQPM-7, DQPM-2 and CM129, were found to be the most stable and promising inbred lines for kernel Zn concentration, while for kernel Fe concentration, no promising and stable genotypes could be identified. Analysis of molecular diversity in 24 selected inbred lines with phenotypic contrast for the two kernel micronutrient traits, using 50 SSR markers covering the maize genome, revealed high levels of polymorphisms (214 SSR alleles; mean PIC value?=?0.62). The phenotypically contrasting and genetically diverse maize inbred lines identified in this study could be potentially utilized in further studies on QTL analysis of kernel micronutrient traits in maize, and the stable and most promising kernel micronutrient-rich maize genotypes provide a good foundation for developing micronutrient-enriched maize varieties suitable for the Indian context.     

Identification of multiple ear-colonizing insect and disease resistance in CIMMYT maize inbred lines with varying levels of silk maysin

Ninety four corn inbred lines selected from International Center for the Improvement of Maize and Wheat (CIMMYT) in Mexico were evaluated for levels of silk maysin in 2001 and 2002. Damage by major ear-feeding insects [i.e., corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae); maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae); brown stink bug, Euschistus servus (Say); southern green stink bugs, Nezara viridula (L.) (Heteroptera: Pentatomidae)], and common smut [Ustilago maydis DC (Corda)] infection on these inbred lines were evaluated in 2005 and 2006 under subtropical conditions at Tifton, GA. Ten inbred lines possessing good agronomic traits were also resistant to the corn earworm. The correlation between ear-feeding insect damage or smut infection and three phenotypic traits (silk maysin level, husk extension, and husk tightness of corn ears) was also examined. Corn earworm and stink bug damage was negatively correlated to husk extension, but not to either silk maysin levels or husk tightness. In combination with the best agronomic trait ratings that show the least corn earworm and stink bug damage, lowest smut infection rate, and good insect-resistant phenotypic traits (i.e., high maysin and good husk coverage and husk tightness), 10 best inbred lines (CML90, CML92, CML94, CML99, CML104, CML108, CML114, CML128, CML137, and CML373) were identified from the 94 lines examined. These selected inbred lines will be used for further examination of their resistance mechanisms and development of new corn germplasm that confers multiple ear-colonizing pest resistance.