Genetic Studies on Mealiness, Dry Matter, Root Number and FreshRoot Yield, in Cassava (Manihot esculenta Crantz)

Abstract

Breeding for increased mealiness, number of roots, dry matter content and good fresh root yield enhancing the production of cassava to meet consumer acceptance for cassava storage root and its products has become the next challenge in cassava breeding in Sierra Leone. These traits are essential for cassava production as they are the most preferred traits for end-use consumption. Data were subjected to statistical analyses using SAS version 9.3. Analytical tools employed included general analysis of variance and diallel analysis of variance for combining abilities and estimates. The mean performance for number of roots per plant ranged from 4.85 to 2.50 for crosses IBA 120004 x I088693 and IBA120004 x TMEB1 with a grand mean of 3.59, while the mean performance for fresh root yield ranged from a highest of 0.80kg/plant, I9100416 x I088693 to 0.23kg/plant UBJ120003 x IBA 120004. Significant differences were observed among the 65 F1 crosses for dry matter (P < 0.01); number of storage roots per family and fresh root yield per family at P < 0.05. General combining ability
(GCA) variance was significant only for fresh root yield per family at P < 0.05 whereas specific combining ability (SCA) variance were significant for dry
matter (P < 0.05) and number of storage roots at P < 0.01 and fresh root yield at P < 0.05. High variability for different traits had also been reported in cassava. The mean FRSY and SRN at the seedling evaluation stage in this study were lower than those reported by Ojulong et al., Mtunda and Tumuhimbise et al., Highest magnitude of positive and significant SCA effects was shown by F1 progenies from crosses UBJ120003 x UCC2001(246), UBJ120003 x TMEB693, UBJ120003 x TMEB 419, UBJ120003 x MM961871, UBJ120003 x I088693, TMEB419 x I088747, TMEB419 x I011368, MM961871 x I9100416, IBA120004 x I088747, IBA 120004 x I088693, IBA961165 x I088693, IBA 961165 x I088693, and I9100416 x I088693. Combining ability analysis for storage root related traits at this early stage was possible because of the high SRN produced by the seedling plants ranging from 1 to 23 storage roots plant−1. his study clearly demonstrates that it is possible to conduct combining ability analysis for storage root related traits at the seedling stage of cassava breeding. This high
SRN was attributed to the method that was used in raising seedlings combined with good growing conditions in Sierra Leone. Findings of this study also demonstrated that it is possible to simultaneously select for yield and quality traits, such as DMC at the seedling stage using simple statistical methods. It was also revealed that breeding strategies for crop improvement should exploit the advantage of both additive and non-additive gene action to be able to achieve the different levels of stages in improving most of these studied traits.