Seed weight mediates effects of pollen on berry weight, ripening, and anthocyanin content in highbush blueberry

Abstract

Blueberry growth differs among individual berries even within the same flower cluster within the same tree. To explain the reason for this phenomenon, cross-pollination with different sources of pollen and self-pollination were carried out to induce variations in the number of seeds per berry, and analyze the effects of pollen on the days to ripen from flowering (DRF), berry weight (BW), and anthocyanin content of berry skin (ANT). In addition, we discuss whether these effects of pollen could be the evidence of metaxenia. Cross-pollination with 4 levels of diluted pollen varied the number of total seeds per berry (NTS) or the number of seeds with brownish seed coat (NBS) and resulted in differences in BW and DRF. Besides, BW, DRF, ANT, NTS and the total seed weight per berry (TSW) also differed significantly among the pollen sources. DRF was highly correlated with NTS, but BW and ANT tended to be more affected by TSW than by NTS. NTS tended to increase in cross-pollination compared with that in self-pollination, whereas single seed weight (SSW) tended to be high in the berry produced by self-pollination that involved fewer seeds. Therefore, differences in pollen source affected not only NTS, but also SSW. Consequently, seed weight may be more appropriate than seed number when assessing the effect of seeds on fruit characteristics.