Study of Silique Shattering Tolerance Genetic and Related Traits in Winter Oilseed Rape Genotypes Using Diallel Cross Method

Although the opening of the silique is a valuable mechanism for the distribution of seeds in nature, it is also a significant problem in oilseed rape cultivation. Seed shedding from siliques at and after maturity is commonly referred to as pod shatter, and it reduces the grain yield of oilseed rape (Brassica napus). This factor, also called dehiscence, can cause losses of up to 50% of potential grain yield if harvesting is delayed and in adverse weather conditions. As a general consideration, canola is susceptible to shattering, and there is little genetic diversity associated with silique shattering tolerance in its commercial lines hence, increasing shatter tolerance is an important breeding objective.

In the present study, eleven parents were used to generate 55 hybrids. The experiment was carried out as a complete randomized block design with three replications at the seed and plant improvement institute. Silique Shattering Tolerance Index (SSTI) using Random Impact Test (RIT) and other related traits were measured during 2018. Griffing's model I of method II was used for the analysis of variance and the estimation of genetic parameters. Correlation coefficients for the studied traits and other calculations were performed using the SPSS software and Excel program.

Analysis of variance of genotypes showed high genetic diversity for the studied traits. Similarly, the general and specific combining ability variances were significant for most traits such as grain yield and the silique shattering tolerance index. This indicates the contribution of additive and non-additive effects in the genetic control of these traits. The general heritability of the studied traits was observed in the range of 78.81% to 93.87%. Correlation coefficients of traits showed a positive and significant correlation between silique shattering tolerance index with grain yield and oil content. Moreover, Zarfam and ES Artist with a good performance and silique shattering tolerance index are considered the best general combiners. Okapi×Zarfam, Nafis×ES Artist, Ahmadi×Nafis, Ahmadi×ES Neptune, Zarfam×ES Neptune, Nafis×ES Natalie, and Nima×ES Natalie are recommended as the best specific combinations for mechanized oilseed rape harvest and improvement of the shattering tolerance trait.

Low specific heritability of grain yield can be due to the more outstanding contribution of non-additive effects than additive effects. Various research studied variable estimation for general and specific combining ability and other parameters due to the difference in genetic materials and different weather conditions.