Factors affecting the number of single silique in Brassica napus.

To improve seed setting rate and get more seeds in siliques of rapeseed, abortion of ovules and seeds were investigated in 36 DH (double hyploid ) materials under 4 pollinating treatments (open pollination, forced selfing, hybridizing and assisted artificial pollination) . The initial number of ovules, normal mature seeds and abortion seeds were investigated to better understand the abortion period and causes. Statistic results showed that the initial ovule numbers of different materials had highly significantly variation, ranging from 23.05 to 36.15 with an average of 29.48. After maturing, the seeds number in single silique was 8.82 - 26.38, with an average of 16.80. The correlation coefficient between the number of ovules and the number of seeds per siliques was 0.77. Average, 56.19% of the initial ovules could develop into mature seeds and nearly 44% ovules aborted during the seed development. The abortion rate was found to be related to genotype as well. The abortion could be divided into 3 types. They were divided by ovules diameter as : a (less than 0.1 mm), b (between 0.1 - 1.0 mm) and c (embryo abortion). They occurred in all 36 materials under 4 treatments. Type a and b were the main types of ovule (or seed) abortion, with average occurrences of 19. 34% and 7.91% respectively. Type c occurred only 1.54%, which might be related to the ceasing of embryonic developmental. These results indicated that the ovules number was related to genotype, and the abortion occurrence and types were also related to genotype. The cause of abortion might be in stigma development, stigma and pollen recognition, and/or in fertilization and initial embryo development. [ABSTRACT FROM AUTHOR]