The investigation of pellicle peelability on Japanese chestnut cultivar of 'Yakko' (Castanea crenata Sieb. et Zucc.)

Japanese chestnuts (Castanea crenata Sieb. et Zucc.) generally have difficult-peeling pellicles even after heating, making easy-peeling pellicle (EPP) an important breeding target. Recently, EPP cultivars 'Porotan' and 'Porosuke' were released by a government-funded breeding program. However, very few genotypes carry the major recessive gene responsible for the EPP trait, resulting in inbreeding within a narrow gene pool. To discover other genetic materials having the potential for EPP breeding, we evaluated the pellicle peelability of 59 accessions (51 Japanese local cultivars and 8 wild individuals) by using the high-temperature oil peeling method. We discovered that 'Yakko' had an exceptionally high pellicle peelability score (87%), close to that of 'Porotan' (94%). The results of segregation ratio analysis of pellicle peelability and genotype prediction by simple sequence repeat (SSR) markers among F1 seedlings suggested that the EPP alleles of 'Porotan' and 'Yakko' are at the same locus. However, a haplotype structure analysis of the EPP genome region with SSR markers revealed that both haplotypes of 'Yakko' differed from those of 'Porotan', suggesting that the EPP gene of 'Yakko' had a different origin from that of 'Porotan' or was inherited from a common ancestor many generations ago.