Variation in rapeseed genotype’s reaction to drought during flowering and identification of tolerant-genotypes selection index

Rapeseed (Brassica napus L.) crop is particularly susceptible to drought at the flowering stage. This study was conducted to (i) assess four genotypes under contrasting water conditions for their reaction to drought and (ii) determine the traits associated with tolerance and yield stability. The experiment was carried out in pots during two cropping years under greenhouse-controlled conditions. From the flowering stage to early seed maturity, the four genotypes were evaluated under two levels of water stress T2 (66% of T1) and T3 (33% of T1), in addition to full irrigation as the control water regime (T1). Results indicated significant effects of genotype, water regime and their interaction on all measured parameters. The genotype ‘Nap9’ was the best regarding seed yield and oil content under the two levels of water stress and for both years. It also exhibited higher root length and higher leaf relative water content than the other genotypes. Therefore, it may be recommended as a valuable germplasm in rapeseed breeding programs for drought tolerance. High branching combined with high leaf relative water content could be a relevant and valuable selection index for this breeding program.