Genetic variation and association among factors influencing storage root bulking in cassava

Abstract

Cassava (Manihot esculenta Crantz) is an important storage root crop with largely unexplored and unexplained potentially valuable genetic variability. Genetic variability is important in selecting suitable genotypes for crop improvement. The present study was aimed at assessing the extent of variability in cassava storage root bulking, based on fresh storage root yield accumulated over time. Twelve cassava genotypes were evaluated in a randomized complete block design at three contrasting locations in Uganda. Assessments were done from 5 to 13 months after planting at intervals of 2 months. Genotype, harvest time, location and their interactions were significantly different for fresh storage root yield and most of the other traits assessed. Estimates of variance components revealed that a large portion of the phenotypic variance was accounted for by the genotypic component for all traits assessed indicative of substantial genetic variability among the genotypes evaluated. This genetic variability is important in a hybridization and/or selection programme because it implies that significant genetic gain through phenotypic selection is possible for the traits assessed. Fresh storage root yield was positively and significantly correlated with storage root girth, harvest index, shoot mass and storage root number. The information generated will inform future breeding initiatives to develop early-bulking cassava genotypes with farmer-preferred traits in Uganda.

Agronomic performance and genetic divergence between genotypes of Manihot esculenta

“…On the other hand, the lowest RY was observed for genotypes 1 (16.63 t ha -1 ) and 12 (15.38 t ha -1 ). Previous studies also observed a positive correlation between RY and number of roots per plant (Rós and São João 2016, Tumuhimbise et al 2015.…”

Genetic parameters and agronomic evaluation of cassava genotypes

“…However, there was no significant difference for NRRP and FRY. Genetic variation for cassava root traits, including root yield, has been commonly identified in different studies in Brazil (Barreto & Resende, 2010;Oliveira et al, 2014Oliveira et al, , 2015 and in Africa (Aina et al, 2007;Ojulong et al, 2008;Tumuhimbise et al, 2015). Possibly, in the present study, the augmented blocks design was not suitable to detect differences for root yield.…”

“…There were positive and significant correlations between PSW and NRP, PSW and FRY, and FRY and NRP (Table 3). These positive and significant correlations were expected, since the increase in root yield has been associated with plant shoot growth and with the increase in the number of roots (Elias et al, 2001;Tumuhimbise et al, 2015). However, a negative and significant correlation was verified between FRY and NRRP, which was also expected, since root rot leads to yield loss.…”

Genetic variation in cassava for postharvest physiological deterioration

“…Means were separated using least significance differences at 5% significance level. The following mixed model, with genotype declared as fixed effects and locations and harvest times as random effects, was used (Tumuhimbise et al 2014) (Equation (2)):…”