Identification of QTLs for Flesh Mealiness in Apple (<i>Malus</i> × <i>domestica</i> Borkh.)

Abstract

During apple (Malus × domestica Borkh.) storage, a loss in fruit firmness can occur. This is frequently associated with mealiness, an undesirable trait. There have been studies, such as phenotypic analyses and transcriptomics, as well as others employing a transgenic approach, focusing on this trait. Certain genetic approaches, such as quantitative trait loci (QTL) approach, however, have not been attempted. In this study, to identify and characterize QTLs controlling flesh mealiness and to investigate their application in apple breeding, we performed classical QTL mapping based on a bi-parental population and a genome-wide association study (GWAS) of mealiness. Phenotypic data for mealiness allowed us to identify two QTLs in the bi-parental family located on linkage group 10. The GWAS discovered significant marker-trait associations on chromosomes 2, 9, and 10. The MdPG1 locus, located on chromosome 10, was identified as the locus with the strongest significance by both QTL mapping and GWAS, suggesting its primary contribution to flesh mealiness. Using a tri-allelic simple sequence repeat marker, Md-PG1 SSR 10kd, 10 kb downstream of the MdPG1 coding sequence, we divided apple accessions into six groups based on their genotypes. Among the six groups, the Md-PG1 SSR 10kd genotype "2/2" had the least mealy phenotype.

Flavor and Texture Characteristics of ‘Fuji’ and Related Apple (Malus domestica L.) Cultivars, Focusing on the Rich Watercore

“…For mealiness, another QTL associated with MdPG1 was detected from different F 1 population [40]. So far, as 'Fuji' descendant, however, 90% of selected cultivars or superior breeding lines have inherited the haplotype of 'Fuji'-derived 'Ralls Janet' at the region of chr1 [10,48].…”

Identification of favorable SNP alleles related to fruit traits in diverse apple germplasm

“…Therefore, there has been a concentrate on the rmness in apple breeding in order to maintain post-harvest fruit quality during long-term storage. According to other studies of QTL for esh rmness, genetic loci related to esh rmness were appeared on chromosome 10 including genomic regions for candidate genes such as 1-aminocyclopropane-1-carboxylate oxidase (ACO) and polygalacturonase (PG) located up to these QTL regions [2,[5][6][7]18]. In this study, meaningful GWAS peaks for esh rmness were found on chromosomes 17, 1, 3, 4, 5, 16, and 10, and SNPs (chromosome 10: 12900899, 28459403) most signi cantly associated with rmness were located 5Mb upstream of PG1 (MDP0000326734) and 4Mb downstream of ACO1 (MDP0000195885).…”

“…is an economically important temperate fruit-tree crop [1], and its industry is globally relatively large. For more advancement of apple industry, many apple breeders are keen interested in development of novel cultivars with high fruit quality traits such as richness of titratable acidity (TA), soluble solids content (SSC), skin color, esh rmness, and weight, which are major factors attracting to consumers' preferences [2][3][4][5][6][7]. However, production of new apple cultivars from conventional breeding is relatively slow and unpredictable owing to its self-incompatibility, high heterozygosity, complex traits controlled by multi loci, and relatively long juvenile period that makes it time-consuming to con rm the traits of the fruit compared with annual crops [3,8,9].…”

“…In plant breeding system, the understanding of genotype-to-phenotype relationships is an important perspective. GWAS can explore genotype-phenotype associations in diverse populations of unrelated cultivars, and investigation of several important quantitative fruit quality traits (titratable acidity, soluble solids content, skin color, esh rmness, and weight) had been performed using GWAS [2][3][4][5][6]21].…”

Identification of favorable SNP alleles related to fruit traits in diverse apple germplasm

“…major factors attracting to consumers' preferences [2][3][4][5][6][7]. However, production of new apple cultivars from conventional breeding is relatively slow and unpredictable owing to its self-incompatibility, high heterozygosity, complex traits controlled by multi loci, and relatively long juvenile period that makes it time-consuming to confirm the traits of the fruit compared with annual crops [3,8,9].…”