Effect of intermittent drought on phenotypic traits of F5 RIL Andean intra-gene cross population (BRB 191 X SEQ 1027) of common bean
Drought is a major constraint to common bean (Phaseolus vulgaris L.) production in East Africa, where irrigation for the crop is very uncommon. The objective of this study was to identify drought tolerant lines and phenotypic traits underlying drought tolerance among 128 F5 recombinant inbred lines (RILs), derived from intra gene pool population, between drought tolerant BRB 191 (source of bc-3) and SEQ 1027. The population was evaluated with eight experimental checks that included BAT 477, CAL 96, DAB 441, DAB 494, and Diacol Calima, NABE 4, SCR 9 and SEQ 1003. A total of 20 phenological, morphological and physiological shoot traits were evaluated, under drought and non-stress conditions, in the field for 2 years (2014 and 2015) at Kawanda in Uganda. New sources of drought tolerance, and previously identified sources of drought tolerance in common bean (BAT 477, DAB 441 and DAB 494), were confirmed based on their superior geometric means and low drought susceptibility. Drought stress in the field significantly affected all measured traits, except harvest index and stem dry weight reduction (P<0.001). Drought significantly reduced yield, yield components and pod harvest index (P<0.01). However, chlorophyll content, canopy temperature, stem dry mass reduction, and 100 seed weight remained stable under season by genotype by water regime treatment interactions (S x G x T). The stability of these traits highlighted their usefulness in selecting for drought tolerance across different environments. Furthermore, pod partitioning index (PPI), harvest index (HI), chlorophyll content and stem dry weight reduction also remained stable under G x T effects. Significant correlations (P<0.001) were maintained between HI and PPI with seed yield under drought stress in field conditions, indicating that photosynthate remobilisation increases yield under drought stress conditions.
Key words: Phaseolus vulgaris, photosynthate remobilisation