Genetic analysis of drought stress response in rapeseed (Brassica campestris and B. napus). I. Assessment of environments for maximum selection response in grain yield

Summary Expectations of yield improvement in environments where drought was the major environmental factor limiting yields were studied in two species of rapeseed. Selection for yield in a drought stressed environment was predicted to be a more efficient selection stategy for yield improvement in dryland situations than selection in a more optimal environment, or selection based on a drought response index. The results indicate that selection for yield in a stressed environment are expected to lead to genetic advances in yield under optimal conditions as well as in a drought index. Selection under well watered conditions, on the other hand, was also expected to lead to correlated increases in yield in droughted environments but to decreases in the drought index. These results were found in both species of rapeseed grown in different water stress situations.The genetic advance in a drought response index was predicted to be greater in B. napus and marginally less in B. campestris if selection was practised for yield in a stressed environment rather than direct selection for the drought index. This was due to the higher heritability estimates in the stressed environments and the positive genetic correlations with yield.