Fudong Jiang

The size of leaves and fruits is a crucial agronomic and economic trait for fruit trees. The ‘Bartlett’ pear is a famous cultivar with succulent and delicious fruit and is cultivated globally. ‘Xiang shuomi’ is a bud sport of the ‘Bartlett’ pear, discovered in our breeding work, and exhibits enlarged leaves and fruits. However, the specific regulatory mechanism of this superior agronomic trait is still elusive. In this study, comprehensive transcriptome and metabolome analyses were performed to explore the differences in gene expression and metabolite accumulation between these two pear cultivars. The transcriptome analysis showed a total of 1279 differentially expressed genes (DEGs), with the flavonoid biosynthetic process being the most significant enriched biological process. Metabolome data indicated the detection of 412 differentially abundant metabolites (DAMs), with the metabolites of flavonoid biosynthesis being enriched significantly. The integrative transcriptomic and metabolomics analysis further confirmed the pivotal role of the flavonoid biosynthetic process in distinguishing the two cultivars. Importantly, the genes that encoded enzymes related to flavonoid biosynthesis, including CHS, CHI, HCT, LAR and CYP75B1, increased their expressions in the ‘Xiang shuomi’ pear. Correspondingly, the metabolites galangin, chlorogenic acid, luteolin and catechin were found to accumulate in the ‘Xiang shuomi’ pear. Overall, this research identified key pathways and genes influencing the fruit and leaf size of pears, providing fundamental information for the high-yield breeding of fruit trees.

Postharvest ripening is correlated to the quality and shelf life of European pear fruit. In this study, the effects of peppermint extract on fruit phenotype, related physiological activities, and aroma components during postharvest ripening of the European pear variety ‘Packham’s Triumph’ were examined. Fruit treated with 2.0 g L⁻¹ peppermint extract for 12 h showed delayed softening by 4 d compared with that of the untreated control group. The peak values of ethylene and respiratory rate in fruit were reduced to a certain extent after peppermint extract treatment; however, the peppermint extract did not delay the occurrence of the respiratory climacteric peak. Peppermint extract treatment also did not significantly increase the content of the characteristic peppermint aroma in pear fruit. Further, widely targeted metabolome analysis revealed 298 significantly different metabolites, with flavonoids (40%) and lipid compounds (15%) accounting for the highest proportion on the first day after treatment. The Kyoto Encyclopedia of Genes and Genomes pathway result showed significant enrichment in the metabolic pathways of biosynthesis of flavonoid, isoflavonoid, flavone and flavonol, linoleic acid, and alpha-linolenic acid metabolism following peppermint extract treatment. The combined analysis of transcriptome and metabolome data showed significant enrichment in linoleic acid metabolism and alpha-linolenic acid metabolism on the first, third, and fifth days after peppermint extract treatment. This study indicates that peppermint extract mainly affects the pear fruit softening process in the early stage after treatment.