Comparison of phenotypic characters of developed mutant lines of rapeseed (Brassica napus L)with the original parents
Thagana, W. M.
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Rapeseed, an important oilseed crop in Kenya and grows well between altitudes of 1830 m ASL to 2740 m above sea. Commercial varieties of rapeseed have ben developed using mutation breeding. The objective of the study was to compare phenotypic characters of developed mutant lines with those of their parents. Seven entries comprising of 3 parents and 4 mutant lines derived from the 3 parents were planted in 2006 in a randomised complete block design (RCBD) with 3 replicates at Njoro, Mau Narok and Molo. Data was taken on various characters. Data analyses were carried out using SAS, General Linear Model (GLM) and Tukey’s test were used to separate the means. Parents as a group versus mutant lines as the other group were compared using contrasts. The entries were highly significant (P<0.01) for plant height, seed yield and seed weight across the sites while primary branches were significant at 5 %. The mutant line-RmD and Rm were the shortest across the sites. Entry RmD had the highest 1,000-seed weight across sites of 4.5 grams. At Njoro, the mutant lines Rm, Km and Tm, which had been selected for early maturity, flowered in less than 62 days compared with the parents, which flowered in more than 67 days. The entry Rm was the first to attain physiological maturity (116 days) but was not significantly different (P>0.05) from Regent (131 days). Although Tm (132.6 cm) was significantly (P<0.05) shorter than Regent (146.3 cm) and flowered early, the yield of Regent (3,734 kg/ha) was not significantly (P>0.05) different from Tm (3,611 kg/ha). Contrasts revealed that mutant lines were highly (P<0.01) significantly different from parents for plant height and yield in all the 3 sites. The contrasts also revealed that mutant lines were highly (P<0.01) significantly different from parents for first flower and days to 50% flowering at Njoro. The mutant lines were (P<0.05) significantly different from parents for physiological maturity. Although the parents were taller and outyielded the mutant lines in all the sites, the mutant lines were the first to flower and matured earlier than the parents at Njoro. The mutant lines were distinct from their parents for phenotypic characters including earliness and height among others. Mutant line RmD, may be crossed with commercial varieties in order to improve the seed weight which is an important component of yield. Mutant lines except Tm in Njoro and Mau Narok, had lower yield when compared with parents in the 3 sites, however, they were early and shorter which are desirable characters. The mutant lines need further testing in more sites alongside 10 other mutant lines that have been developed