Evaluation of the effects of dry and rainy seasons on cassava rootsnutritional contents and tuber rot disease

Background: Cassava, (Manihotesculenta Crantz), is a crucial crop for ensuring food security in sub-Saharan Africa, and intermittent drought conditions affect its proximate composition and disease susceptibility. Methods: A field experiment was carried out at the National Root Crop Research Institute, Umudike, Umuahia in Abia State, Nigeria, and at the Department of Plant Science and Biotechnology, Imo State University to evaluate the cassava root proximate composition, and tuber rot incidence. The experimental field was arranged in a randomized complete block design with three replications. Four varieties of cassava, which include enhanced cultivars, TME419, NR87/184, UMUCAS 46, or 07/0539, as well as two indigenous varieties, L1 and L2, were cultivated for a duration of 12 and15 months. The cassava roots were harvested in July (wet season) and in December (dry season). Results: The results indicated that there were statistically significant variations (P≤0.005) in the cassava's root proximate composition, and rot incidence in different varieties and monitoring periods. All varieties exhibited greater accumulation of crude protein, crude starch, and carbohydrates during the dry season compared to the rainy season. All the varieties saw more ash buildup during the rainy season compared to the dry season. The fungal pathogens responsible for cassava rot are Botryiodiplodiatheobromae (producing black rot), Fusariumoxysporium (causing dry rot), Aspergillusflavus (associated with soft rot), Rhizopusstolonifer, and Sclerotiumrolfsii. During the rainy season, B.theobromae had the highest percentage incidence at (34.78%), while S. rolsfii had the lowest percentage incidence (8.70%).During the dry season, F. oxysporium had the highest percentage incidence (26.3%), while S. rolsfii had the lowest percentage incidence (10.52%). Rainy season recorded higher rot incidence than dry season. Conclusion: The study demonstrates that the proximate composition of cassava root is influenced by factors such as age, the season of harvest, and variety, and these provide a better understanding of the proximate composition response of cassavavarieties under dry and wet growing conditions, which can be recognized and used integrally to improve food quality.