Insights into the Physiological and Molecular Mechanisms Underlying Highbush Blueberry Fruit Growth Affected by the Pollen Source

Abstract

Pollination is an important factor affecting fruit development in highbush blueberry (Vaccinium corymbosum L.). In general, planting several different blueberry cultivars increases the chances of cross-pollination and ensures high-quality fruit production. However, little is known about the effects of the pollen source on fruit development in blueberry. The aims of this study were: 1) to understand the effects of the pollen source on fruit size and quality; and 2) to explore the mechanisms underlying fruit development affected by the pollen source. We first characterized the pollination effect on fruit development using 14 different pollination combinations for several years and found that the number of mature seeds and fruit size differed significantly among the fruit pollinated by different pollen sources. Significant correlations between the number of mature seeds and fruit size were found in most combinations, whereas the number of mature seeds was not correlated with other fruit quality parameters such as sugar concentration. Our results and those of previous reports showed that the number of mature seeds, which was influenced by the pollen source, was a primary determinant of fruit size. Time-course observation during fruit development revealed that fruit weight and cell size significantly differed between self-pollinated and cross-pollinated fruit from 30 days after pollination onwards. To explore the molecular mechanisms underlying berry growth affected by developing seeds, we compared gene expression changes between self-pollinated and cross-pollinated fruit. Transcriptome analysis of fruit at 10 days after pollination suggested that auxin signaling pathways were enhanced in cross-pollinated fruit compared with self-pollinated fruit. We thus hypothesize that activated auxin signal transduction underlying early stage seed and fruit development may promote fruit cell enlargement during the early stage of fruit growth in highbush blueberry.

Comparative transcriptome and functional analyses provide insights into the key factors regulating shoot regeneration in highbush blueberry

“…RNA was extracted from the leaves of in vitro shoots (0 days) and explants on 1.0 mg/l TDZ medium collected at 2, 4, and 8 days after culture. For RNA-seq in this study, a reference genome consisting of 55 648 representative genes selected from 128 559 genes in the tetraploid ‘Draper’ genome was utilized [ 23 , 24 ]. Principal component analysis (PCA) indicated that a significant change in the gene expression profile occurred at 2 days postculture (2 d) in both cultivars ( Supplementary Fig.…”

“…The sequencing reads were initially trimmed using Fastp [ 49 ] with default parameters for the removal of adapter sequences and low-quality bases (quality score <15). In this study, a reference genome consisting of 55 648 representative genes selected from 128 559 genes in the tetraploid ‘Draper’ genome was utilized [ 23 , 24 ]. The clean reads were mapped to the aforementioned reference transcriptome using Bowtie2 (version 2.3.5.1) [ 50 ].…”

Toward evidence-based decision support systems to optimize pollination and yields in highbush blueberry

“…Likewise, southern highbush genotypes showed 63 and 65% improvement in fruit set and fruit size with hand cross-pollination, respectively. The magnitude of fertility gains may depend on the degree of inbreeding for a given genotype (Hellman and Moore, 1983;Hancock, 1988, 1990) and on the pollen donor (White and Clark, 1939;Cremins, 1952;Gupton, 1984Gupton, , 1997Czesnik et al, 1989;Gupton and Spiers, 1994;Huang et al, 1997;Ehlenfeldt, 2003;Martin K. et al, 2019;Nagasaka et al, 2022). Cross-pollination can also result in a decrease of ripening time (Supplementary Table 1) and an increase of anthocyanin content (Doi et al, 2021).…”

Optimal Pollination Thresholds to Maximize Blueberry Production

“…Highbush blueberry, Vaccinium corymbosum L., is a mass flowering crop dependent on animal-mediated pollination (Eeraerts et al, 2023). In general, increasing pollen deposition through flower visitation promotes blueberry production and reduces ripening time (Danka et al, 1993;Dogterom et al, 2000;Drummond, 2019;Nagasaka et al, 2022). This pollen demand is mostly covered by stocking honeybee hives --Apis mellifera L.--in blueberry fields (Bushmann and Drummond, 2020;Cavigliasso et al, 2021;Rollin and Garibaldi, 2019), with this species providing ~80% of flower visits to blueberry crop along its cultivation range (Eeraerts et al, 2023).…”