Pleiotropic QTL Underlying the Dormancy and Reducing Sugar Content in Potato Tubers Uncovered by Conditional QTL Analysis

Dormancy and reducing sugar content in tubers are important traits of potato and are typical quantitative traits. Deciphering the genetic basis of potato tuber dormancy and reducing sugar content is a prerequisite for improving the two traits. DorB5.3 , a stable major dormancy QTL (quantitative trait locus) previously mapped across seven environments, has been found to co-localize with REC_B_05-1 , a QTL controlling reducing sugar content in potato tubers. In order to determine whether DorB5.3 was a pleiotropic QTL or not, a conditional QTL mapping was carried out, and the results suggested that DorB5.3 and REC_B_05-1 were the same QTL, controlling the dormancy and reducing sugar content in potato tubers simultaneously. Conditional QTL mapping also uncovered three pairs of epistatic QTLs which were independent of the reducing sugar content and were significant for deciphering the genetic basis of dormancy. Five genes were picked out as putative causal genes controlling DorB5.3 , according to the genome annotation and transcriptomic data. The pleiotropic DorB5.3 along with the negative correlation between the causal and resultant traits provided a possibility that potato breeders could prolong the dormancy period and scale back the reducing sugar content of potato tubers in one breeding program. The results of this study could pave a way for understanding the genetic basis of both dormancy and reducing sugar content in potato breeding programs.