Development of Microsatellite Markers and QTL Mapping for Yield in Cassava (Manihot esculenta Crantz)

In this study, a genetic linkage map of cassava was constructed using an F₁ population of a cross between ‘Huay Bong 60’ and ‘Hanatee’. A total of 640 SSR and 1,500 EST-SSR primer pairs were developed during this study in collaboration with the Kazusa DNA Research Institute. To construct the cassava map, the developed SSRs and EST-SSRs, and 900 of the SSR and EST-SSR markers obtained from the International Center for Tropical Agriculture database and previous publications were used to screen for informative polymorphisms between parental lines. The results showed 727 informative markers which were used to genotype 100 samples of the F₁ population. Genotypic data were analyzed to construct the map using the JoinMap 3.0. The map is comprised of 307 SSR and 203 EST-SSR loci, covering 1,420.3 cM, distributed in 23 linkage groups with an average marker distance of 4.54 cM.  

Phenotypic data of fresh root yield was evaluated at Rayong Field Crops Research Center in 2009. The data were integrated with the genetic map for identification of significance QTL using MapQTL 4.0. One QTL, Yld1, associated with fresh root yield that located on LG6 was detected, and accounted for 21.5% of PVE. The closet marker was MeES699 which showed significant of KW at P<0.5. The QTL controlling fresh root yield trait with large effects in this study will be useful for positional gene cloning and applicable to molecular breeding of cassava through MAS, in order to select and develop new cassava lines with high yield.