Document Type : Research Paper
Associate Professor of Genetic and Plant Breeding, Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-8311, Iran
Former MSc Student of Plant Breeding, Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-8311, Iran.
Physiological basis of genetic variability in drought response and its association with yield
and related indices is not clear in Brassica. In this study 36 accessions belonged to seven
species of Brassica were evaluated under normal, moderate and severe stress environments.
Physiological traits along with seed yield, seed yield components, oil content and two selection
indices (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 on
the STI, B. carinata and B. juncea were identified as the superior species in moderate stress
condition while B. oleracea was the most tolerant under intense stress. Moderate drought stress
significantly increased the ratio of chlorophyll a to chlorophyll b (Chla/Chlb) while severe stress
decreased it. Although relative water content (RWC) had positive correlation with STI, its
heritability was low. Chlorophyll content (TChl) was associated with STI and had moderate
heritability. Positive correlation was found between proline content and DSI under both stress
conditions. Results showed large variation is among studied species for drought tolerance and
related traits indicating that selection in this germplasm would be useful. Changes in
chlorophyll content can be recognized as a key component affecting drought tolerance in