Genetics of Red Flesh Colouration in Kiwifruit (Actinidia chinensis)

Kiwifruit is the most important horticultural crop for the New Zealand export market. The Actinidia germplasm is highly variable and kiwifruit breeders utilize this diverse genetic material to develop new cultivars with unique fruit characteristics, such as high health attributes and novel flavours and colours. We examined the genetic determinants of red fruit flesh colouration in Actinidia chinensis assist breeders in developing new red cultivars using molecular markers. Preliminary genome scans based on visual scores were performed by genotyping by sequencing (GBS) in a red x gold-flesh factorial, complemented by whole genome sequencing of parents to provide a catalog of allelic variation. Two A. chinensispopulations of 310 and 128 individuals segregating for red flesh intensity with the same male parent were utilized for more detailed QTL analysis. Phenotyping was done using digital image analysis.

GBS was used to construct high density SNP based genetic maps using 2325 polymorphic SNP markers. QTLs associated with red colouration were detected on Chromosomes 9 and 28. Tandemly duplicated MYB transcription factors co-locate with the Chr9 QTL. Molecular markers were developed and validated in the Plant & Food Research breeding programme and marker-assisted selection has been initiated on parental material.