Variability and genetic diversity study in an advanced segregating population of rice with bacterial blight resistance genes introgressed

ABSTRACT Bacterial blight disease of rice caused by Xanthomonas oryzae pv. oryzae is one of the most important widespread disease around the globe and can cause severe yield reductions of up to 30% of the total yield. Genetic variability was studied in 54 families of CB 174 R × IRBB 60 rice with bacterial blight resistance genes introgressed at the Department of Rice, Tamil Nadu Agricultural University, Coimbatore, India. Traits such as plant height and the number of productive tillers per plant were found to have negative skewness in this study, indicating the duplication of gene effects. Panicle length and the number of grains per panicle were found to have positive kurtosis, indicating gene interactions. The phenotypic coefficient of variation was slightly higher than the genotypic coefficient of variation for all traits, indicating that the observed variation was not only due to genotypic but also due to the environmental effect on the expression of these traits. High heritability coupled with high genetic advance as a percent of the mean was observed for plant height. Moreover, moderate heritability coupled with high genetic advance as a percent of the mean was observed for the single plant yield of rice. Cluster and principal component analyses revealed that the 54 F2:3 families were grouped into three clusters based on six agro-morphological traits. Clusters III and II had higher mean values for most of the studied traits than cluster I. Intercrossing lines from distinct clusters can be identified and crossed to generate larger variability to produce desirable recombinants for higher yield with a wide genetic base.

摘要：由稻黄单胞菌稻致病变种（Xanthomonas oryzae pv. oryzae）引发的水稻白叶枯病是全球分布最广泛的重要病害之一，可导致最高达30%的总产量严重损失。本研究于印度哥印拜陀市泰米尔纳德邦农业大学水稻系，对导入白叶枯病抗性基因的CB 174 R × IRBB 60水稻的54个株系家族开展遗传变异分析。研究发现，株高、单株有效穗数等性状呈负偏态分布，提示基因效应存在重复；穗长、每穗粒数呈正峰态分布，表明存在基因互作。所有性状的表型变异系数均略高于基因型变异系数，说明观测到的变异不仅源于基因型差异，还受环境对这些性状表达的影响。株高表现出高遗传力配合高遗传进展（以均值百分比计）；水稻单株产量则表现出中等遗传力配合高遗传进展（以均值百分比计）。聚类分析与主成分分析结果显示，基于6项农艺形态性状，54个F2:3株系家族可划分为3个类群。类群Ⅲ和类群Ⅱ的多数被测性状均值均高于类群Ⅰ。通过对来自不同类群的株系进行杂交，可创造更丰富的遗传变异，进而筛选获得兼具高产与宽泛遗传基础的优良重组型材料。