Fine-mapping and validation of the genomic region underpinning pear red skin colour

Abstract

Red skin colour is an important target trait in various pear breeding programmes. In this study, the genetic control of red skin colour was investigated in an interspecific population derived using the descendants of the red sport European pear cultivar ‘Max Red Bartlett’ (MRB) and the red-blushed Chinese pear cultivar ‘Huobali’. Approximately 550 seedlings from nine families were phenotyped for red skin over-colour coverage (Ocolcov) and the intensity of red over-colour (Ocolint) on a 0–9 scale, and genotyped using genotyping-by-sequencing. Genome-wide association analyses were conducted using 7500 high-quality single nucleotide polymorphisms (SNPs). Genomic regions on linkage groups (LG) 4 and 5 were found to be associated, and the best SNP (S578_25116) on LG4 accounted for ~15% of phenotypic variation in Ocolcov and Ocolint. The association of S578_25116 with Ocolcov and Ocolint was successfully validated in a sample of ~200 European and Asian pear accessions. The association with red skin at locus S578_25116 was not present in Asian pear accessions, suggesting its close proximity to the MRB’s Cardinal gene. Several putative candidate genes, including MYB transcription factors ( PCP027962 and PCP027967), were identified in the quantitative trait locus region on LG4 and await functional validation.

Crop genetics: What makes a pear red?

Researchers in New Zealand have produced a map of genetic variants linked with red skin color in pears, opening the door to identifying the genes responsible. Satish Kumar and others at the New Zealand Institute for Plant and Food Research Limited measured the skin color of 550 hybrid pear seedlings and sequenced their genomes. Combining these data produced a map of 7,500 variants throughout the genome and identified those associated with red skin color. The most significant variant accounted for about 15% of the color variation. Further analysis of that genomic region revealed several genes which might be related to red skin color. The genomic map produced by this study will improve breeding efficiency by making it possible to screen seedlings for fruit color, but further research is necessary to characterize the candidate genes.