Genotype by environment interactions of Indian mustard (Brassica juncea L.) and canola (B. napus L.) in Mediterranean-type environments: 1. Crop growth and seed yield

Adaptation of Indian mustard (Brassica juncea L.) and canola (B. napus L.) to low rainfall, short season, Mediterranean-type environment in south Western Australia was studied by investigating the effects of genotype, environment and their interaction on crop growth and seed yield. Seed yield of mustard and canola in low rainfall environments (Merredin, Mullewa and Newdegate) were higher when sown early in the season (May). Mustards were generally more adapted than canola to stressful environments associated with low rainfall, high temperature and late sowing as inferred from principal component and Finlay Wilkinson analyses. Mustard produced significantly higher dry matter compared to canola (3.91 t/ha versus 2.63 t/ha) particularly in later sowings. Average phenotypic stability of mustard genotypes (887.1.6.1, Muscon and 82 No 22-98) was mainly associated with their greater tolerance to stressful environments (low rainfall, high temperature and late sowing), early vigour, shorter pre-anthesis phases and greater dry matter production. Mustard genotypes (JM 25 and JM 33) with greater tolerance to stressful environments showed above average phenotypic stability. Seed yield was strongly correlated to final above ground dry matter, post-anthesis dry matter, harvest index (HI), total number of pods/plant, 1000 seed weight, final plant height and number of primary branches. Duration to flowering and number of seeds/pod were not significantly correlated with seed yield. Although mustards produced more dry matter compared to canola, it was not translated into higher seed yields due to their lower efficiency in converting dry matter to seed yield (low harvest index). Yield structure of the two species differed in that canola has fewer pods and more seeds/pod than mustard.