Combining Ability And Genetic Effect Analysis Of Drought Tolerant Traits During Seedling Stage In Brassica Napus L.

Rapeseed is one of the four major oil crops in China. Drought has endangered the production of rapeseed. Breeding for drought tolerant rapeseed is one efficient way of reducing yield loss due to water deficiency. Lots of systematical and deeply researches on drought tolerance have been done in corn, rice, soybean, wheat, peanut and so on. There are many reports about combining ability and genetic effect analysis on yield and quality traits in rapeseed, while those in drought tolerant traits just a little.In this paper,49 hybrids were made by diallel crossing with seven different drought-tolerant varieties (Brassica napus L.). The traits relative to drought tolerance, such as leaf area, root length, shoot fresh weight, root fresh weight, total fresh weight, shoot dry weight, root dry weight, total dry weight, chlorophyll content and soluble protein content, were measured under drought stress during seedling stage. The performance differences were analyzed between drought treatment and control and the genetic effect and as well as general combining ability (GCA) and special combining ability (SCA) of these drought-tolerant traits were estimated by Griffing Methed I. The objective were to lay the foundation for mechanism researching of drought tolerance and breeding of drought-tolerant variety. The results were as follows:1. Chlorophyll content and soluble protein content under stress of water deficiency were rised significantly in seedling stage. Compared with control, the content of chlorophyll increased by 54.17%, soluble protein increased by 354.99% in average. However, leaf area, shoot fresh weight, root fresh weight, total fresh weight, shoot dry weight, root dry weight, total dry weight were decreased under stress of water deficiency by 46.65%,42.05%,54.07%,43.11%,27.96%,34.31%,29.57%, respectively, which were significant. There were no significant differences between drought treatments and controls of root length.2. Combining ability analysis indicated that:There were significant differences among 10 traits of 49 crosses. The GCA estimate values of leaf area, shoot dry weight, total dry weight, chlorophyll content and soluble protein content in Kelina-2 were 0.4461,0.01443,0.0154,0.2126 and 0.0116, respectively. Meanwhile, the GCA estimate values of leaf area, shoot fresh weight, total fresh weight, chlorophyll content in 07W285-4 were 2.3787,0.3300,0.3002 and 0.1905, respectively. Those drought-tolerant traits'general combining ability values were much higher than others. The higher SCA estimate values of hybrids were 07W285-4x88009, (Buyu X 32)x36-Ai,07W288-3x36-Ai, 88009xL43K6#,07W285-4xL43K6# through comprehensive analysis.3. Estimation of genetic parameters indicated that:Variances of special combining ability of leaf area, root length, shoot fresh weight, root fresh weight, total fresh weight, shoot dry weight, root dry weight, total dry weight, chlorophyll content, soluble protein content were significantly higher than thoes of general combining ability, indicating these traits were contolled mainly by gene dominant effects and gene additive effects were relatively weak, dominant gene effects played a relatively a leading role. These 10 drought-tolerant traits had lower narrow heritabilities and were selected in appropriate late generation.