EVALUATION OF SELECTED CASSAVA GENOTYPES FOR YIELD TRAITS, DISEASES REACTION AND ROOT POSTHARVEST QUALITY

Abstract

Cassava is a multipurpose crop that serves as a lifeline for many people. However, postharvest losses linked to postharvest physiological deterioration (PPD) undermine its maximum utilization. PPD reduces starch quality and renders the roots unpalatable and unmarketable. Hence, there is need to identify genotypes that delay PPD. Therefore, this study was initiated to evaluate the yield performance of selected cassava genotypes, determine relationship between root PPD and yield traits and identify storage system that can prevent early onset of root deterioration in cassava. The study was carried out using seventeen elite cassava genotypes and five commercial checks, arranged in a randomized complete block design with three replications at the experimental site of International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria in the 2017/2018 and 2018/2019 cropping seasons. The genotypes were assessed for physiological deterioration at 3, 7 and 10 days after harvest. Data obtained were subjected to analysis of variance and significant means were separated using Tukey HSD test. Also, phenotypic and genotypic coefficients of variation, broad sense heritability, genetic advance estimates and genotypic correlation were computed. Results of the study revealed that there were significant (P<0.05) variations among genotypes for best traits evaluated. IITA-TMS-IBA100256 had the highest percentage dry matter content of 39.18% for the two seasons while IITA-TMS-IBA100199 had least (25.33%). The highest fresh root yield of 32.81 t/ha was produced by IITA-TMS-IBA100190 in the two seasons. Result on the post-harvest quality showed a water loss increase in dry matter content during storage, and also post-harvest physiological loss was observed for all the genotypes evaluated at 3, 7 and 10 days after harvest. Heritability estimates varied between 2 for number of rots to 92% for total carotene in 2018 while it ranged from 11 for number of rots to 90 % for cassava mosaic disease in 2019. PPD at 7 days after harvest had positive and significant genotypic correlation with PPD at both 3 and 10 days after harvest. There was a progressive decrease in the quality of cassava roots during storage with the highest PPD found among the cassava roots 10 days after harvest. From the study, only PPD at 7 days after harvest was significant which is not enough to confirm its performance among the classes of days (3, 7 and 10 DAH) used for the PPD evaluation under sun and shade. Path analysis was carried out to identify traits with significant direct effects PPD (7 DAH). PPD (10 DAH) has the highest level of genotypic correlation with PPD (7 DAH) but it was not significantly different from PPD (3 DAH). The result showed that genotypes that are tolerance to physiological deterioration depend on the physiological properties of each variety irrespective of where it was stored. IITA-TMS- IBA100256, IITA-TMS-IBA100273, IITA-TMS-IBA100290, and IITA-TMS-IBA100252 are genotypes with delayed post-harvest physiological deterioration and they could be used in cassava improvement program.