A study on the fertility grading system of cytoplasmic male sterile line of MI CMS in rapeseed (Brassica napus L. )

The fertility grading system in the progeny of the cross between CMS line and restorer line was studied by using the MI CMS line and its maintainer and restorer in rapeseed (Brassica napus L. ). The results showed that the pollen quantity, the viable pollen ratio and the effective podding ratio were significantly different among various fertility grades. The plants of grade 1, 2 and 3 were classified as male sterile ones, and the plants of grade 4 as male fertile ones. According to the grading system, the ratios of the number of male fertile plants to that of male sterile plants were 3: 1 in F2generation and 1: 1 in BC1 generation, indicating that there exited one pair of dominant fertility restoration gene in MI CMS.