Full Length Research Paper

QTL analysis for early yield in a pseudo F₂ population of cassava

E. Okogbenin^1,2*, J. Marin^1,3 and M. Fregene¹

¹International Center for Tropical Agriculture, CIAT, Km 17, Recta Cali-Palmira, AA6713, Cali, Colombia.

²National Root Crops Research Institute, NRCRI, Umudike, PMB 7006, Umuahia, Abia State, Nigeria.

³Univerisdad del Tolima, Ibague, Tolima, Colombia.

*Corresponding author. E-mail: E.Okogbenin@cgiar.org. Phone: 234-8057401924.

Accepted 7 December, 2007

Genetic mapping of early bulking in a full-sib population of cassava was continued in a selfed family of 268 cassava plants derived from a single progeny of the full-sib population.  The pseudo F₂ population was analysed with 122 segregating SSR markers.  A previously constructed linkage map of cassava consisting of 22 linkage groups covering 1236.7 cM, with an average marker distance of 18 cM was used for this study.  The F₂ population was evaluated for components of early yield, namely dry root yield (DR) at 7 months, harvest index (HI), and weight of fresh foliage (FF). Interval mapping, with single- and two-QTL models, was used to identify QTLs. The single-QTL model identified three QTLs each for DR, FF, and HI.  The two-QTL model approach identified groups of QTLs that together explained 33% for FF, 43.5% for DR and 36% for HI. The identification of QTLs involved in early yield is an important step toward understanding quantitative genetic variation of early yield and implies reconsideration of breeding strategies for improvement of this complex trait.

Key words: Cassava, early root yield, linkage map, molecular marker-assisted selection QTL, SSR markers.