Browsing by Author "Namugwanya, Margaret"

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Response of common bean genotypes grown in soil with normal or limited moisture, with special reference to the nutrient phosphorus
(MDPI : Agronomy, 2018-07-30) Namugwanya, Margaret; Tenywa, John Stephen; Otabbong, Erasmus
Drought and phosphorus deficiency in the soil are the major production limitations of common beans (Phaseolus vulgaris L.) in Sub-Saharan Africa. This study measured the yield responses of low phosphorus-tolerant common beans to drought stress. A field experiment was conducted under two drought conditions codenamed, non-drought-stress (NDS) and drought-stress (DS). The former was located at Mukono Zonal Agricultural Research and Development Institute (MUZARDI) in Mukono District, characterised by rainfall of more than 400 mm season−1. The latter was situated at Wabinyonyi in Nakasongola District, characterised by less than 300 mm season−1; both in central Uganda. Treatments included the two study conditions (NDS and DS); and four test bean genotypes, AFR703-1, AFR 708, JESCA, and MCM 2001, against a local check, K131. A water deficit of 156 mm season−1 was observed in the DS site causing a drought intensity index (DII) of 40%. That pattern contrasted considerably in the NDS site where the actual rainfall did not significantly (p > 0.05) vary from the required water by the bean plant. Whereas genotypes AFR703-1 and AFR708 out-yielded the local check in NDS by 213 and 681 kg ha−1, respectively; their grain yield harvested was comparable to the control yield in DS. When grown under DS, low P-tolerant beans, especially the AFR703-1 and AFR708, survived drought stress through faster development by reducing the number of days to flower, reach physiological maturity and develop seeds. AFR703-1 and AFR708 sufficiently withstand drought stress, and are therefore recommended for inclusion in cropping systems that are characteristically constrained by the combined soils’ P deficiency and/or drought.
Uncovering adaptive mechanisms to water deficit in low soil phosphorus tolerant common bean genotypes
(Food Agricultural Sciences and Technology (FAST), 2025-05-12) Namugwanya, Margaret; Taulya, Godfrey; Basamba, Twaha Ali; Tenwya, John Stephen
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.