Abstract

S4-06

Genetic Analysis and QTL Mapping of Early Root Bulking in an F₁ Population of Non-inbred Parents in Cassava (Manihot esculenta Crantz)

Okogbenin E.^1,2 and Fregene M.¹

1.        International Center for Tropical Agriculture, AA6713, Cali, Colombia         m.fregene@cgiar.org

The genetic basis underlying early bulking in cassava was studied in a replicated, multi-locational trial using 144 F₁ progeny derived from an intra-specific cross between two non inbred parents.  A second sequential harvest experiment examined the relative importance of eight yield-related traits on early bulking and their QTLs during the crop growth cycle.  Our objectives were to identify traits (and genes controlling them) strongly associated with early yield as a first step to marker-assisted improvement of the trait.  A total of 18 QTLs controlling early yield were identified in the first experiment.  Multiple linear regression analysis and stepwise regression of early yield on eight yield-related traits revealed harvest index, dry foliage weight and root diameter as the most important factors associated with early yield.  A total of 27 QTLs were detected for these traits, 2 for dry foliage weight, 8 for harvest index and 17 for root diameter.  The individual effects of the QTLs identified ranged from 7% to 33% of the phenotypic variance explained.  The identification of a number of QTLs with positive effect for increased early yield provides an opportunity for marker-assisted selection and improvement of early bulking potential in cassava.