Genotype by environment interactions of Indian mustard (Brassica juncea L.) and canola (Brassica napus L.) in Mediterranean-type environments: II. Oil and protein concentrations in seed

The effects of genotype, environment and their interaction on oil and protein concentrations of seed in mustard and canola were investigated under field conditions in Mediterranean-type environments of south Western Australia over two seasons. Genotype, environment and their interactions showed large effects on oil and protein concentrations in both species. Oil and protein concentrations varied between crop species (mustard versus canola) and genotypes compared to those between environments. The effect of environment on protein concentrations was larger compared to that on oil concentration. The oil concentration ranged from 37.3 (Oscar) to 38 (887.1.6.1) and 40% (Monty). The protein concentration ranged from 22.9 (887.1.6.1) to 24.5 (Monty), 26 (Oscar) and 28.5% (Muscon).Variation in oil and protein concentrations between environments was largely accounted for by the interacting effects of total rainfall, post-anthesis rainfall, post-anthesis duration, average maximum post-anthesis and pre-anthesis temperatures and soil pH. Oil concentration of mustard and canola in Mediterranean-type environments was higher, but protein concentration was lower in environments where post-anthesis period was wetter and cooler.Seed oil concentration was inversely proportional to seed protein concentration in mustard and canola genotypes. Increase in seed yield increased the oil concentration, but decreased the protein concentration. Percentage increase in oil per unit increase in seed yield was higher in canola than in mustard genotypes, whilst percentage reduction in protein concentration per unit increase in seed yield was higher in mustard than in canola genotypes.