热带水稻优异种质资源的表型遗传多样性分析

有效管理和充分挖掘遗传多样性丰富的稻种资源对水稻育种具有重要意义。利用15个表型性状对来自9个热带国家和地区的127份热带水稻育种优异种质进行综合评价,比较分析不同来源热带水稻优异种质的表型差异和遗传多样性指数。结果表明：热带水稻种质资源表型性状差异明显,数量性状的变异系数为7.0%～23.8%,平均为12.04%,其中单株穗数比较大,谷粒长较小;Shannon-Wiener多样性指数分析结果表明,15个表型性状遗传多样性指数变化为0.603～2.066,平均为1.579,其中每穗总粒数比较高,穗型较小;9个不同来源地的热带水稻资源多样性指数为0.780～1.547,平均为1.219。不同来源的热带水稻种质各性状变异范围较大,各性状间存在显著差异,遗传多样性指数较高,可进一步发掘优异资源和有利基因,为培育和筛选优良热带水稻品种提供亲本来源。     

Phenotypic variations of wheat cultivars from the North China Plain in response to cadmium stress and associated single nucleotide polymorphisms identified by a genome-wide association study

Understanding the genetic mechanisms for cadmium (Cd) uptake and translocation in common wheat (Triticum aestivum) is of significance in food Cd contamination control. In this study, a diverse panel of 132 wheat cultivars was collected from the North China Plain. The cultivars were evaluated in terms of their phenotypic variations in response to Cd stress and subjected to a genome-wide association study (GWAS) to identify single nucleotide polymorphisms (SNPs) associated with the phenotypic variations at the seedling stage. Significant phenotypic variations with high heritability were observed among the wheat cultivars exposed to 40 μmol L^-1 Cd for the studied traits, including root length (RL), shoot length (SL), root and shoot dry biomasses (RDW and SDW, respectively), root and shoot Cd concentrations (RCD and SCD, respectively), and Cd translocation factor (TF). Mean RCD, SCD, and TF ranged from 1.0 to 33.8, 0.125 to 2.022, and 0.009 to 0.321 mg g^-1, respectively. Cluster analysis showed that wheat cultivars with higher RL, SL, RDW, and SDW under Cd stress were able to accumulate more Cd in root, leading to a lower Cd TF. Mixed linear model-based association analysis detected 17 novel significant marker-trait associations (MTAs), four of which were significant at a genome-wide scale. Most of the significant MTAs controlled Cd TF and explained 17.17%-26.47% of the phenotypic variations. Some of the SNP loci were physically close to a reported Cd-related quantitative trait locus or gene on wheat chromosomes. Results of this study provided a list of wheat cultivars with the potential of low Cd accumulation and enriched our knowledge on the genetic basis of Cd uptake and translocation in wheat. Pyramiding breeding of superior alleles detected in this study may additionally reduce Cd accumulation of improved wheat cultivars with excellent agronomic traits.     

番荔枝不同家系果实表型性状的差异

为了筛选出适宜广西石漠化地区栽培的番荔枝（Annona squamosa）新品种,2012年从越南岩溶地区引进了番荔枝15个家系的果实,通过对其果实表型性状差异性分析,结果表明：各家系之间果实纵径、单果质量、糖度以及种子的长度、种宽、种厚、千粒重均有显著差异,而各家系之间果实横径差异不显著,果实纵径最大是27号,果实横径最大是11号,单果质量最重是23号,糖度最高是20号。     

玉米自交系表型性状主成分聚类分析研究

玉米作为重要的饲料作物和粮食作物,优良杂交种的选育和推广应用为玉米增产做出了突出贡献。杂种优势利用是玉米育种研究的重要内容,杂种优势理论建立在亲本遗传差异之上,因而种质遗传多样性研究是杂种优势利用的前提。该研究利用一批从国内外引进玉米优良种质资源选育而成的稳定自交材料,为有效利用这批新自交系,明确其应用潜力,采用了表型性状分析对其进行了遗传多样性研究,结果表明:供试的57份自交系间表型性状变异都集中在一个较小的范围内,各自交系间的欧氏遗传距离变幅为1.010 8~11.078 7,平均遗传距离为4.934 5。当遗传距离为5.41时,可将57个自交系分为4个类群,各类群自交系各具特点,其中3号材料、9号材料植株较高,果穗较粗大,穗长、行粒数和百粒重等经济性状表现良好,是一个很好的高产育种潜力亲本;46号材料生育期较短、植株矮小,可在选育早熟、矮秆玉米组合上重点应用;其余自交系系各具特色,可结合不同育种目标有针对性地加以改良和利用,对玉米育种实践具有一定指导意义。     

新疆野苹果叶形性状变异及其与SSR标记关联分析

以从新疆天山地区新疆野苹果600个无性系中筛选得到的18个优系为研究对象,调查其叶形性状变异,并进行了SSR分子标记分析,探究叶形性状与SSR标记间的相关关系。结果表明,调查的15个叶形性状在无性系间均存在极显著差异;平均变异系数最大的为叶尖角α(达到25.39%),叶形指数L1/L3最小(仅为10.31%);叶片长的重复力最大(达到0.967),叶形指数L1/L3最小(仅为0.495)。以15个叶片性状为依据,可将各无性系完全区分开,并分为3类,各无性系间的遗传距离变化在1.293~7.235间。用均匀分布在17个染色体连锁群上的30对多态性SSR引物对18个无性系进行聚类分析,可将各无性系完全区分开,并可分为4类,各无性系间的遗传距离为0.089~0.689,平均遗传距离为0.433。所有叶形性状聚类结果与所有SSR标记聚类结果不相关。以单一叶形性状聚类结果与经过筛选的部分SSR标记聚类结果进行相关分析,绝大部分达到极显著相关,且大部分引物组合表现为累积效应,表明叶形性状与部分SSR位点具有紧密关联。     

Phenotypic correlations between maize inbreds and their single cross hybrids in short season areas

Summary This study was conducted to determine the relationships among various agronomic traits in inbreds, hybrids and between inbreds and their progeny of maize in short season areas. Phenotypic correlations of each measured trait between as well as among hybrids and inbreds were not the same. The highest correlation coefficient (r=0.78) was obtained between days to anthesis and yield. The high yielding inbreds did not necessarily give rise to high yielding progeny. Given that days to anthesis plays an important role in two major traits (yield and moisture) for hybrids, an emphasis on optimum anthesis dates during inbred development could be a useful criterion for the prediction of hybrid performance in short season areas.     

Rank correlation among parametric and nonparametric measures of phenotypic stability

Summary There is an increasing number of stability parameters for genotypes grown in different environments. It is therefore useful to study the statistical relations between these parameters. One approach is the calculation of rank correlations between different stability parameters in empirical data sets. In the data analysed there are high rank correlations between ecovalence W_i, deviation mean square s² _di, the nonparametric measures S_i ⁽¹⁾, S_i ⁽²⁾, and two new measures R_i and L_i as well as between environmental variance S² _xi and regression coefficient b_i. The results suggest that S_i ⁽¹⁾, S_i ⁽²⁾, L_i, and R_i can be used as alternatives to W_i and the stability variance ² _i. This may be worthwhile, if certain statistical assumptions do not hold, particularly if significance testing is needed.     

The degree of phenotypic similarity of near-isogenic lines of the wheat cultivar Centana with their recurrent parent

Summary The degree of phenotypic similarity of Centana and its near-isogenic lines (NILs) has been investigated. Some NILs have a disease reaction, a gliadin pattern and a yield level which differs from Centana. This means that they still possess many donor genes. One of the NILs, Shortana, must be a derivative of a backcross line crossed with an unknown genotype resulting in a good yielding variety.     

The degree of phenotypic resemblance of the near-isogenic lines of the wheat cultivar thatcher with their recurrent parent

Summary Thatcher, 16 of its near-isogenic lines (NIL) and 8 donors were investigated for the degree in which the NILs phenotypically resembled their recurrent parent. In general the NILs have a good phenotypic resemblance. In a few NILs characters occur that are not seen in Thatcher. In some cases these are found in the donor indicating the presence of donor genes other than the marker gene in the NIL. In other cases a character possessed by a NIL is not present in Thatcher or in its donor. In such cases either inhibitor genes may play a part, or the donor accession that accompanies the set of NILs may not be the donor used to breed the NIL. Two causes are possible. One is that the donor was a mixture of genotypes, the other is contamination.The presence of donor genes other than the marker Lr gene(s) in a NIL may lead to unexpected results or, what is worse, to wrong conclusions.     

Selection for resistance to Septoria nodorum in wheat

Summary A population of 572 F₂ derived F₃ lines from six crosses were used to estimate parameters relevant to selection for resistance to Septoria nodorum of wheat. Lines were grown in disease free (fungicide sprayed) and inoculated microplots in 2 replications of a split-plot design in a single environment in 1977. Average yield reduction due to disease was approximately 50%; this was associated with an average septoria score of 50% on the flag leaf, an average septoria score of 42% on the head, and a reduction of 37% in seed weight. Low S. nodorum scores were correlated with late heading date, tall plant height, high grain yield, and high seed weight in diseased plots, and high seed weight % (seed weight in diseased plots expressed as a percentage of seed weight in fungicide sprayed plots).Restricted selection indexes were used to study the relative contributions of disease escape, true resistance, and tolerance to variability in grain yield in diseased plots, seed weight in diseased plots, and seed weight %. True resistance appeared to be the most important factor causing variation in grain yield in diseased plots and seed weight %. Tolerance and escape seemed to be more important for seed weight in diseased plots.Heritabilities of S. nodorum scores on the flag leaf and head were 63% and 52%, respectively. Leaf and head scores could be used most effectively as selection criteria to upgrade resistance in a population before harvest.Selection for high seed weight % slightly reduced yields in disease free plots, although yield in diseased plots and seed weight in diseased plots were increased. However, selection for increased yield or increased seed weight in diseased plots improved yield in disease free plots. It is suggested that direct selection for yield or seed weight in diseased plots is likely to achieve more desirable goals than selection for seed weight %.