Inheritance of the Md-ACS1 gene and its relationship to fruit softening in apple (Malus × domestica Borkh.)

Abstract

The 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene is a member of the ACS gene family that is involved in apple ( Malus x domestica Borkh.) fruit ripening. Presence of an allele ( Md-ACS1-2) of this gene is associated with low internal ethylene concentration in some apple cultivars. In this study, inheritance of Md-ACS1 was determined for 50 apple cultivars/advanced selections and 101 F(1) seedlings from five populations. Following this, the softening pattern of apples stored at 20 degrees C for up to 40 days was examined using 35 fruiting cultivars/selections of defined Md-ACS1 status. Md-ACS1 is inherited in a Mendelian fashion and was found to be linked to fruit softening. Maturity season of genotypes also significantly affected fruit softening. Late-season genotypes in the Md- ACS1-2/2 class had the slowest rate of softening, while early-season Md- ACS1-1/1 genotypes had the most rapid softening rate. The implications of these results are discussed in relation to parental selection and breeding for storage ability in apple.

Ethylene Biosynthesis and Perception in Fruit

“…For example, the 'Orin' genotype is Md-ACS1-1/1-2, and 'Orin' produces more ethylene than 'Fuji', whose genotype is MdACS1-2/1-2. The allelotype of MdACS1 correlates with the rate of fruit drop (Sato et al, 2004), but does not always correlate with the rate of fruit softening (Oraguzie et al, 2004).…”

Map position and functional allelic diversity of Md-Exp7, a new putative expansin gene associated with fruit softening in apple (Malus × domestica Borkh.) and pear (Pyrus communis)

“…We tested these markers because of their known association between allelotypes and apple fruit softening (Oraguzie et al 2004;2007;Costa et al 2005). Significance of differences among apple and pear genotype classes was calculated using one way ANOVA followed by Newman-Keuls test.…”

“…Md-ACS1 and Md-ACO1 are two candidate genes that are known to be associated with fruit softening in apple (Harada et al 2000;Oraguzie et al 2004 andCosta et al 2005). Both functional markers were mapped in Prima × Fiesta population (Costa et al 2005).…”

“…Md-ACS1 and Md-ACO1 are two genes involved in the ethylene pathway that have been associated with softening of fresh and/or cold-stored apples (Harada et al 2000;Oraguzie et al 2004Oraguzie et al , 2007Costa et al 2005). While the …”

“…Studies carried out on apple-segregating populations have identified important QTLs for firmness and flesh texture on linkage groups LG01, LG08, LG10, LG15 and LG16 (King et al 2000;Maliepaard et al 2001;Seymour et al 2002). Novel insight into fruit-firmness control in apple has recently been presented via a candidate-gene approach investigating the effects of Md-ACS1 and Md-ACO1, two genes involved in ethylene production during the ripening stage, on fruit softening (Harada et al 2000;Oraguzie et al 2004Oraguzie et al , 2007Costa et al 2005). Md-ACO1 was mapped on LG10 within the 5% confidence interval border of an important QTL for fruit firmness, genetically linking ethylene production to the rate of apple softening (Costa et al 2005).…”