Physiological traits related to drought tolerance in Brassica

Physiological basis of genetic variability in drought response and its association with yieldand related indices is not clear in Brassica. In this study 36 accessions belonged to sevenspecies of Brassica were evaluated under normal, moderate and severe stress environments.Physiological traits along with seed yield, seed yield components, oil content and two selectionindices (stress tolerance index, STI and drought susceptibility index, DSI) were studied.Moderate and intense stress caused reduction in seed yield and the most studied traits. Based onthe STI, B. carinata and B. juncea were identified as the superior species in moderate stresscondition while B. oleracea was the most tolerant under intense stress. Moderate drought stresssignificantly increased the ratio of chlorophyll a to chlorophyll b (Chla/Chlb) while severe stressdecreased it. Although relative water content (RWC) had positive correlation with STI, itsheritability was low. Chlorophyll content (TChl) was associated with STI and had moderateheritability. Positive correlation was found between proline content and DSI under both stressconditions. Results showed large variation is among studied species for drought tolerance andrelated traits indicating that selection in this germplasm would be useful. Changes inchlorophyll content can be recognized as a key component affecting drought tolerance inBrassica.