SEED PRODUCTION OF HYBRID SUMMER RAPE IN THE FIELD USING THE POL CYTOPLASMIC MALE STERILITY SYSTEM: A FIRST ATTEMPT

Hybrid summer rape (Brassica napus L.) seed production blocks were established at two locations in Manitoba in 1986 and 1987 to examine the effect of distance from the pollen source on seed yield, (both total and hybrid) and percent hybridity of seed produced on rows of a male sterile line of the open pollinated population B. napus cultivar, Marnoo, possessing the pol cytoplasmic male sterility inducing cytoplasm. A 10:1 ratio of male sterile line (A-line) to pollen parent was employed. Leaf cutter bees (Megachile rotundata F.) were used as the pollen vector between the two parents. In 1986, no significant differences in total seed yield were found among A-line rows, while in 1987, significant differences in total seed yields of A-line rows were found. Differences in hybrid seed yields among A-line rows were significant for all locations and years. Leaf cutter bees were found to be effective pollinators of the A-line plants. Less than half and less than a third of the seed produced on the A-line rows in 1986 and 1987, respectively, was hybrid seed. The high percentage of non-hybrid seed present in the seed lot may have been due to incomplete male sterility of the Marnoo A-line population. Total seed yields, hybrid seed yields and percent hybridity all declined linearly as distance from the pollen source increased. Improvement in the degree of male sterility of the Marnoo A-line population and/or a reduction in the 10:1 ratio of parents, and subsequent maximum A-line row to R-line row distance, will be necessary if hybrid summer rape seed production using this pol CMS A-line is to be commercially viable.Key words: Brassica napus L., CMS, hybrid, hybridity