The validation of two major QTLs related to the timing of spring bud flush in Camellia sinensis

Abstract

The timing of spring bud flush (TBF) in tea plants (Camellia sinensis) is an adaptive critical and economically important trait; thus, it has been a focus of many tea-breeding programs. Previously, we reported the mapping of two major and partial linked TBF QTLs onto the LG01 of C. sinensis using a full-sib population of ‘Longjing 43’ × ‘Baihaozao’. In this study, we further tested the QTL stability and expression variation in different years, experimental sites, and crossing parents. We genotyped 157 additional F1 individuals from the ‘Longjing 43’ × ‘Baihaozao’ cross and 173 F1 individuals from ‘Wuniuzao’ × ‘Longjing 43’ cross with 16 and 17 SSR markers on LG01, respectively. We also recorded the TBF trait of the two populations at Hangzhou and/or Shengzhou sites in the spring of 2014, 2015 and/or 2017. The TBF QTLs were significant (P < 0.001 at the chromosome-wide level) in all tested years, sites, and populations, but the explained phenotypic variation ranged considerable (26.2–40.5%, two QTLs were considered together in the Interval Mapping). Interestingly, the QTLs only segregated in ‘Longjing 43’ among the three parents involved. After grouping the individuals by the genotypes of the two markers closest to the QTLs, a maximum difference of 9.22 days for the average TBF was observed between the earliest and latest groups.