A recent study from Northwest A&F University, in collaboration with Yale University, in the United States, has resequenced a number of apple genomes, providing greater insight into their role in fruit firmness and ripening.
Firmness is a key quality characteristic, affecting storage, transportability, and marketability, and is just one of many apple qualities (including flavour, colour and sweetness) which are regulated by complex genetic networks. However, previous efforts to map firmness-related genes faced challenges due to apple’s long juvenile period and genetic complexity, so the specific genetic factors driving natural variations in firmness have been unclear.
In the study, using from ‘Fuji’ and ‘Cripp’s Pink’ varieties, researchers constructed a high-density genetic map using 5014 bin markers covering 17 apple chromosomes. They identified 60 QTLs associated with fruit-related traits, among which a major locus on chromosome 3 stood out. In particular variants of the gene MdNAC5 were found to alter the encoded amino acid from methionine to leucine were identified and found to relate to ripening period and firmness.
“Identifying MdNAC5 as a major genetic regulator of apple firmness is a milestone in fruit crop genomics,” said Dr Yazhou Yang, one of the study’s corresponding authors. “Our findings not only deepen the understanding of ripening control in climacteric fruits but also provide a direct molecular target for apple breeding programs aiming to improve storage and consumer qualities. By manipulating MdNAC5 alleles, we could tailor apples to meet specific market demands, extending shelf life without compromising taste.”
The researchers also say that the discovery opens up exciting possibilities for precision breeding in apples. By selecting specific MdNAC5 variants, breeders can engineer cultivars with tailored firmness levels and ripening times, optimising apples for longer storage, better transport resilience, and enhanced consumer appeal.
