| Heterosis phenomenon is existed commonly in living nature. Utilizing heterosis is one of the most effective ways to increase yield in crops. In order to apply heterosis more efficiently, scientists have been made every effort for a long time to probe into the genetic basis and the method of prediction for heterosis. The development of molecular markers and its application in biological researches had provided technological base for dissecting heterosis in crops. Some results showed that epistasis interactions play an importance role as the source of heterosis in rice. Rapeseed is one of the most important crops, and is also one of the most successful crops in heterosis utilization worldwide. To explore the sources of heterosis in rapeseed could enrich the genetic knowledge about crop heterosis. Besides, male sterility (MS), especially CMS (cytoplasmic male sterility), is the main way to exploit rapeseed heterosis in China. To search for new method, analyze the genetic differences of parents and genetic effects on their offspring for yield traits etc, could have significances in broadening ways for heterosis utilization and breeding for hybrids with high heterosis.In this study, 3 double low self-incompatible lines and 22 inbred pure line varieties from different origins, were used to produce 66 hybrids by hand pollination within a North Carolina 11 (NC II) mating design. These hybrids, together with their parents, were tested for yield and oil content in sequence two years in Wuhan, China. SSR, ISSR, AFLP and RAPD techniques were employed to assess genetic diversity in the 25 parental materials, and the relationship was analyzed between genetic diversity and F1 performance. Based on the evaluation results of field experiment and molecular markers, SI-1300 and Eagle were selected as parents to establish F2 segregating population. F2-3 families were planted in Wuhan and Jingmen to determine agronomic traits. F2 plants and the 25 parental materials were analyzed by SSR and AFLP to construct genetic linkage map and to detect quantitative trait loci (QTL) for important agronomic traits. Furthermore, the basis of heterosis in rapeseed was discussed and the power of different methods for prediction of hybrid performance and heterosis was compared. The main results are as follows:1. Heterosis of double low self-incompatibility in Brassica napus1.1 The results from field experiments showed that seed yield/plant of 66 hybrids had positive mid-parent heterosis which ranged from 5.5% to 64.11% with a mean of29.42%. Heterosis for 3 components of yield per plant was in the sequence: total number of siliques per plant>seeds/silique>1000-seed weight.1.2 Significant heterosis for seed oil content was also observed, but it was less than that of yield per plant. Among 66 hybrids, the mid-parent heterosis for seed oil content ranged between -1.55% and 7.44% with an average of 3.13%. 64 hybrids, which accounted for 97.0% of the total, had positive heterosis.1.3 First branches and their siliques contribute most part for yield per plant and its heterosis. So, the two were the key yield traits.1.4 Results from combining ability analysis showed that yield per plant and its 3 components, total number of siliques per plant, seeds/silique and 1000-seed weight of F1 hybrids were affected by both additive and non-additive effects (including dominant and epistasis effects) of genes. The additive effects for yield per plant and total number of siliques per plant were lower than those for seeds per silique and 1000-seed weight. Seed oil content was mainly affected by additive genie effects.1.5 Parental effects on the performance of FI hybrid depended on the types and the values of combining abilities. The higher combining abilities parents had, the greater effects on FIS they made. The parental effects on FI hybrids were greater for traits controlled mainly by additive genie effects than for traits affected by both additive and non-additive effects.1.6 In hybrid breeding, the combining abilities of parent...
|
PDF Full Text Request