Morpho-physiological screening under controlled conditions reveals promising drought tolerance in Ghanaian soybean ( <i>Glycine Max</i> (L.) Merr.) germplasm for improved performance

Abstract Background : Soybean ( Glycine max (L.) Merr.) is a crucial oilseed crop for global food security. However, drought stress limits its productivity and causes significant global yield loss. In arid regions such as the Guinea Savanna agroecology, which spans northern Ghana, Burkina Faso, Togo, Benin, and Nigeria, yield losses can reach 100%. Erratic rainfall patterns due to climate change exacerbate production challenges, particularly during flowering and pod development stages. This vulnerability is particularly acute in the Southern Guinea Savanna of Nigeria and Northern Ghana, where soybean plays a vital socio-economic and nutritional role for rural communities. This region has distinct wet and dry seasons, with drought frequently coinciding with critical reproductive stages and further worsening yields. Improving soybean cultivation in Ghana demands screening for drought-tolerant genotypes suited to its agro-ecological conditions. This study aimed to evaluate 56 soybean cultivars under water scarcity conditions and identify those demonstrating resilience and susceptibility to drought. Methods : The experiment was conducted in a screen house with minimum and maximum temperatures of 22°C and 37°C, respectively. A randomized complete block design with three replications was used. Drought stress was imposed at R1 to R3 growth stages by withholding water for 4 weeks. The Rank Summation Index (RSI) was used to identify and select the best-performing genotypes. Results : Ten cultivars (SARI EXP 1, SARI EXP 13, Favour, SARI EXP 40, Gyedie, Soung-pungun, SARI EXP 8, Toondana, SARI EXP 20, and SARI EXP 14) were identified as moderately tolerant. Their RSI values range from 131 to 193, implying that these genotypes were moderately tolerant. Independent validation trials under the same conditions confirmed SARI EXP 1 to be the most drought-tolerant among the genotypes studied. The most drought-sensitive genotypes were SARI EXP 9, SARI EXP 25, and SARI EXP 34. Moderately tolerant cultivars displayed better water retention, delayed leaf senescence, and sustained growth under stress. Conclusions : Some genotypes were moderately tolerant to drought stress and can be used for further improvement. This study provides a foundation for the introduction of exotic lines to improve climate-resilient agriculture in drought-prone regions of Ghana. Owing to the limited drought tolerance found in the germplasm, future research integrating biotechnological approaches such as mutation breeding, introduction of foreign genotypes, and CRISPR/Cas-mediated gene editing is recommended to accelerate the development of drought-tolerant lines.