Study the genetic variation of rice seed vigour by multivariate statistical methods

Background and objectives: Seed vigour is the resultant of a broad range of physiological processes which have genetic background. The study of genetic variation, play an important role in enhancing the ability of breeders in selection and breeding operation. This study aimed to evaluate rice genotypes with the physiological and morphological characteristics related to seed vigour and grouping them in order to achieve good parents for rice breeding and hybridization program.
Materials and methods: To study the genetic diversity of rice seed vigour, 49 rice genotypes were evaluated in a completely randomized design with three replications in 2013 in Rice Research Institute of Iran-Rasht. In this study, some morphological and physiological traits related to germination and seedling growth were measured under standard germination conditions. In order to estimate the relationship between the traits, the correlation coefficients were calculated and then stepwise regression analysis were used to determine the traits that have great role in explanation of seed vigour variation. In this study, after normality test by Kolmogorov-Smirnov method, factor analysis to grouping the traits was performed by principal component analysis.
Results: The results showed that the effect of genotype was significant for the traits related to seed vigour such as germination rate, uniformity of germination, number of normal seedling, dry weight of seedling, length of seedling, conversion efficiency of depleted seed reserve, vigour index, germination index and energy index that reflects the diversity of seed vigour between the genotype investigated. With regard the vigour index as most important trait, some traits such as length of radicle, length of shoot, length of seedling and germination rate have the most significant and positive correlation coefficient to vigour index. According to the results stepwise regression, length of seedling, germination rate and dry weight of radicle had more contribution in the vigour index variations. Factor analysis determined four factors that accounted 83/83% of total variations among genotypes. Based on the trait coefficients in per factor, the first factor as germination vigour, the second factor as seedling vigour, the third factor as seed physiology and fourth factor as seed physical factor were nominated. In first and second factors, germination index, germination uniformity, D05 and D95 (time it takes to reach germination percentage to 5 and 95 of maximun), germination rate, germination energy, vigour index, dry weight of radicle, dry weight of shoot, dry weight of seedlings and seedling length were caused 63% of the total variation. Cluster analysis based on the more important traits in the first and second factors distinct rice genotypes into 3 clusters.
Conclusion: In general, the present study by appropriate separation of rice genotypes based on the seed vigour in tree groups (native, improved and imported) showed that seed vigour in native genotypes was lower than improved and imported genotypes.