Enhancing drought resistance in African yam bean (Sphenostylis stenocarpa (Hochst. ex A. Rich.) Harms) through silicon nanoparticle priming: A multi-accession study

The impact of drought on crop productivity and growth is substantial on a global scale. Reports of crop failures due to drought are widespread in Africa. This study aims to investigate the effects of silicon nanoparticle (Si-NP) seed priming on drought tolerance in ten Sphenostylis stenocarpa accessions. Seeds in the treatment/drought-stress group were rinsed and soaked in 100 mg/L Si-NP for 24 h, whereas control seeds were soaked in double distilled water. Plants were grown for 90 days, then subjected to 21 days of drought stress. Seed morphological characters, leaf area (LA), water use efficiency (WUE), leaf relative water content (LRWC), root-shoot ratio (RSR), tolerance index (T.I), malondialdehyde content (MDA), proline, superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) parameters were measured on the 7th, 14th and 21st days of drought stress. LA was significantly decreased in Si-NPs treated seeds of TSs 12 and TSs 77, whereas the WUE remained statistically similar in TSs 101 and TSs 158 throughout the study (p < 0.05). RWC significantly increased in drought-stressed TSs 157, indicating a high water balance, while TSs 101 maintained consistent T.I. and RSR values (p < 0.05). MDA content decreased significantly in TSs 157 and TSs 158 (p < 0.05), indicating reduced oxidative stress. TSs 11, TSs 12, TSs 144, TSs 153, and TSs 311 proline levels were statistically similar to those of controls, exhibiting a balanced osmotic protection. Si-NP treatment increased SOD and CAT activities in TSs 158 (p < 0.05), enhancing antioxidant defense mechanisms. Conversely, APX activities decreased in most accessions during early drought stages, signalling impaired ascorbic acid-mediated detoxification of hydrogen peroxide. Si-NP primed seeds of TSs 101 and TSs 158 emerged as the best-performing accessions under drought stress. These findings highlight the potential of Si-NP seed priming in enhancing S. stenocarpa drought tolerance, with significant implications for improving cultivation in water-deficient areas and breeding drought-tolerant varieties. This research contributes to understanding S. stenocarpa resilience and its potential role in ensuring food security and sustainability.