QTL mapping and transcriptome analysis to identify genes associated with green/russet peel in Pyrus pyrifolia

Peel colour is a very important appearance quality and is strongly associated with commercial value. Green, russet and partially russet peels are observed in the fruit of Pyrus pyrifolia. Currently, the mechanisms of peel russeting in fruit development are still uncertain. Two pear cultivars, 'Zaoshengxinshui' (russet peel) and 'Qiushui' (green peel), and 92 offspring were sequenced by specific-locus amplified fragment sequencing (SLAFseq) to isolate SNPs to identify the QTLs. The results showed that 8,545 SLAF tags were used to construct the genetic map with a genetic distance of 2,486.18 cM. Two QTLs were related to peel colour: qColour-LG9.1 and qColour-LG9.2 (LOD >5.2). A total of 73 and 64 genes were annotated in qColour-LG9.1- and qColour-LG9.2related chromosome regions, respectively. Transcriptome analysis revealed the expression of all genes. Four differentially positively expressed genes, PpRAX3, PpHAT22, PpKN1, and PpC3H23, were found in the qColourLG9.1-related chromosome region. The transient overexpression of these genes showed that PpC3H23 could increase the peel russeting ratio, thus implying that PpC3H23 might play important roles in peel russeting. Transcriptome analysis also found 403 differentially expressed genes in peel russeting, including transcription factors (MYB, HD, and BHLH) and functional genes related to fatty acid, glycerolipid, cutin, suberine and wax biosynthesis (GDSL, KCS, GPAT, HHT, etc.). Altogether, the results of the present study provide new insights into the molecular mechanism underlying peel russeting in P. pyrifolia.

Automated summary

This study explored the molecular mechanism underlying peel russeting in Pyrus pyrifolia by identifying QTLs and related genes for peel color through SLAFseq. The results revealed two QTLs related to peel color and provided insights into the genetic basis of peel russeting in Chinese pear fruits. Additionally, transcriptome analysis identified differentially expressed genes associated with peel russeting, including transcription factors and functional genes involved in fatty acid, glycerolipid, cutin, suberine, and wax biosynthesis.