Combining Ability for Nitrogen Use Efficiency in a Diallel Cross of Indian Rapeseed (Brassica rapa L.)

Genetic variation, combining ability and character relationships among yield attributing characters including nitrogen use efficiency were evaluated at two levels of N fertilization in a diallel cross of Indian rapeseed. Three toria (TS-38, JT 90-1, TS-67) and three yellow sarson parents (NRCYS 05-03, YSH 401, B9) and their diallel F1s excluding reciprocals were evaluated at 0 and 60 kg N/ha during Rabi 2012-13. Variation between N levels was significant. Genotypes x N interactions were significant for some characters including seed and biological yield per plant. High to moderate genetic variation, high broad sense heritability and high genetic advance were recorded for nitrate reductase activity. Pooled analysis of combining ability exhibited significant variation in gca and sca effects for most of the characters. Interactions of gca and sca with N levels were observed only for a few characters. YSH 401 was the best general combiner for morpho-physiological yield attributes while JT 90-1 was the best general combiner for seed yield per ha. Seed yield per plant was positively correlated with biological yield and NUE at N60. Nitrogen use efficiency was highly heritable with high genetic variation and genetic advance. TS-38 was the best parent for mean performance and gca effect for NUE. Among the crosses, JT 90-1 x YSH 401 and YSH 401 x B9 showed high mean performance and sca effects.