QTL Mapping of Cyanogen Content in Cassava Root

Cassava (Manihot esculenta Crantz), an important food source and industrial feedstock, is a cyanogenic crop. With the concerning on possible health effect and environment toxicity, this project aimed to identify QTL associated with the cyanogen content in cassava root. QTL identification was not only used to assist breeding program, but also to gain understanding of the loci and underlying genes and their effects. In this study, cyanogen content of ‘Hanatee’ (low cyanogen content), ‘Huay Bong 60’ (high cyanogen content) and their F₁ progenies were evaluated in 2008 and in 2009 at Rayong province, and in 2009 at Lop Buri province, Thailand using picrate paper kit. Linkage map and QTL analysis was performed using JoinMap and MapQTL, respectively. The result showed that, the cyanogen content of the population showed continuous variation with transgressive segregation. The correlation coefficients among years and locations were significantly detected. The derived linkage map consisted of 303 SSR markers, distributed on 27 linkage groups and covered 1,328 cM. The average distance between markers was 5.8 cM. Five QTL underlying cyanogen content were detected based on MQM analysis. The LOD scores of detected QTL ranged from 3.77-5.75 and percentage of phenotypic variation explain (PVE) ranged from 15.9-26.0%. The strongest QTL, CN09R1 showed the LOD value of 5.75 and it explained 26.0% of the variation in cyanogen content. There was no common QTL found across years and locations, but single marker analysis of CA344, a marker linked to CN09R2, was significant in all evaluated years and locations.