Physiological traits determining tolerance to intermittent drought in the Capsicum annuum complex

The use of physiological traits directly-linked to mechanisms of drought tolerance (DT) as selection criteria could accelerate the development of tolerant varieties. To identify such physiological traits in chilli pepper(Capsicum annuum. L.), we screened a range of diverse genotypes, a series of parental breeding lines produced from C. annuum and C. frutescens/C. chinense crosses, under well-watered and water-stressed (65% depletion of available soil water) conditions in the field with a movable rainshelter. Water regime x genotype interaction was significant (p < 0.05) in the majority of measured traits, which showed significant genotypic variation under the two water regimes. Stomatal conductance (g(s)) showed strong positive correlations with yield under both water regimes. Furthermore, relative reduction of g(s) in response to drought positively correlated with relative yield reduction. Canopy temperature (T-c) showed significant negative correlations with yield in both water regimes. Lower yield reductions due to drought were associated with lower increases of T-c across the genotypes. Similarly, lower reductions in shoot relative water content were strongly correlated to lower yield reductions. Yield under drought (Y-d) showed significant positive correlation to maximum rooting depth and dry root weight. Greater flower numbers and conversion of flowers to pods, traits indicating the DT of reproductive processes positively correlated with Y-d. Factor Analysis showed that the above physiological, growth and reproductive traits constituted composite traits which underpin DT in chilli. As such, they can be used as screening tools in identifying drought tolerant germplasm in breeding programmes of Capsicum annuum.