Uncovering adaptive mechanisms to water deficit in low soil phosphorus tolerant common bean genotypes

Abstract

Water-Deficit and low soil phosphorus (P) are major constraints for common bean (Phaseolus vulgaris L.) cultivation in sub-Saharan Africa (SSA). Tolerant varieties offer cost-effective alternatives to irrigation and fertilizers. This study examines how low soil P-tolerant common bean genotypes adapt to Water-Deficit through leaf morphology, physiology, and root development in greenhouse and field conditions. AFR703-1, AFR708, and K131 were arranged in a completely randomized design under Well-Watered and Water-Deficit conditions, with P applied at 0, 6, and 16 mg P kg⁻¹ soil. In the field, identical genotypes were arranged in a randomized complete block design with P applied at 0, 12, and 32 kg P ha⁻¹ under Well-Watered and Water-Deficit Environments. AFR708 showed a significant (P < 0.001) reduction in RWC (26%) under Water-Deficit without P mitigated by higher P levels, while AFR703-1 and K131 showed no significant difference (P > 0.05) under similar conditions. AFR703-1 and K131 exhibited significantly (P < 0.05) lower specific leaf area in Water-Deficit than Well-Watered conditions, contrasting with AFR708. Similarly, LMR in the studied genotypes decreased (P < 0.001) and with rising P under Water-Deficit, with diverse trends in Well-Watered conditions. AFR703-1 and K131 recorded higher NAR in Water-Deficit than Well-Watered conditions, contrary to AFR708. AFR genotypes decreased significantly (P < 0.001) showed enhanced root development in Water- Deficit, including increased adventitious, tap, and lateral roots, higher total biomass, and finer root length compared to Well-Watered conditions, despite lower grain yields, notably in Nakasongola site. Overall, AFR703-1 holds promise as a breeding parent for enhancing Water-Deficit resilience and P tolerance in common bean production, despite yield reduction under stress conditions.