Abstract: The timing of spring bud flush (TBF) is an important agronomic trait of tea plants, which has great effects on the flavor quality and economic benefits of tea. In this study, to discover key candidate genes regulating TBF, a F₁ population of ‘Longjing 43’× ‘Baihaozao’ comprising 327 offspring was used and a two years’ investigation of TBF were performed in the tea garden. Based on the high-density genetic map constructed from the F₁ population, QTL mapping for the sprouting index (SPI) of tea plants was performed using MapQTL 6.0 and GACD 1.2 software. The phenotypes of SPI in 2022 and 2023 show significant trait segregation and exhibit obvious quantitative trait characteristics in the progeny population. MapQTL 6.0 was identified as a primary QTL (qSPI-5-1), which explained 18.30% (2022) and 7.60% (2023) of phenotypic variations, respectively. GACD1.2 software identified two stable QTLs (qSPI-1, qSPI-5-2), which explained 2.75%-18.40% of phenotypic variations. While qSPI-5-2 and qSPI-5-1 were largely overlapped. The confidence intervals of the above QTLs were compared to the reference genome of tea plants, and 23 candidate genes related to the TBF were found by function annotation analysis. These results provided theoretical references for further investigation on the regulatory genes and molecular mechanisms of spring bud flushing in tea plants.

Key words: tea plant, timing of spring bud flush, QTL, candidate genes