عنوان مقاله [English]
Background and Objectives
Although the opening of the silique is an useful mechanism for the distribution of seeds in nature, it is also one of the major problems in the cultivation of rapeseed. Seed shedding from siliques at and after maturity is commonly referred to as pod shatter, It reduces the grain yield of rapeseed (Brassica napus). This factor also called dehiscence, can cause losses up to 50% of potential grain yield if harvesting is delayed and in adverse weather conditions. As 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.
Materials and Methods
In order to generate 55 hybrids, eleven parents were used in this study. The experiment was carried out as a complete randomized block design with three replications at seed and plant improvement institute. Silique Shattering Tolerance Index (SSTI) using Random Impact Test (RIT) and other related traits were measured during 2018. The Griffing's model I of method II was used for analysis of variance and estimating genetic parameters. In this research, correlation coefficients for investigated traits and other calculations were performed using SPSS software and Excel program respectively.
Analysis of variance of genotypes showed that there is high genetic diversity for studied traits. Similarly, the general and specific combining ability variance were significant for most of traits such as grain yield, as well as the silique shattering tolerance index. This subject indicates the contribution of additive and non-additive effects in the genetic control of these traits. General heritability of studied traits was observed in the range of 78.81% to 93.87%. Correlation coefficients of traits showed that there was a positive and significant correlation between silique shattering tolerance index with grain yield and oil content. Zarfam and ES Artist with a good performance and silique shattering tolerance index are considered as the best general combiner. 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 combination for mechanized rapeseed harvest and improvement of the shattering tolerance trait.
Low specific heritability of grain yield can be due to the greater contribution of non-additive effects compared to additive effects. Various research studied variable estimation for general and specific combining ability and other parameters. this may be due to the difference in genetic materials and different weather conditions.