Estimations of Heritability and Breeding Value for Postharvest Fruit Softening in Apple

Abstract

<jats:p>Progenies from 38 unbalanced crosses using 20 apple (<jats:italic>Malus</jats:italic> ×<jats:italic>domestica</jats:italic> Borkh.) cultivars/selections as parents were evaluated for changes in flesh firmness after harvest in two seasons to determine the mechanism of inheritance of fruit softening. The change in firmness was fitted by linear regression, and the softening rate (N·d<jats:sup>−1</jats:sup>) expressed as the regression coefficient was used as the phenotypic value of softening after harvest. Fruit were stored under 20 °C and 85% relative humidity after harvest for up to 40 days. The softening rates in the progeny populations were distributed continuously around the softening rates of parents, despite a distinct segregation in the degree of mealiness at 30 days of storage. The narrow-sense heritability of the softening rate was estimated by parent-offspring regression, and the estimate was high (h<jats:sup>2</jats:sup> = 0.93). Because the softening rate can be influenced by mealiness, an undesirable trait in the apple industry, the progenies were divided into individuals with and without mealiness, and the breeding values of the parents were estimated based on the softening rate of the nonmealy progeny. The softening rate of the nonmealy progeny was analyzed using a mixed linear model and the restricted maximum likelihood method, with general combining ability (GCA) as parental effects and specific combining ability (SCA) as parental interaction effects. The variance of GCA was significant, but the variance of SCA was small and nonsignificant. The narrow-sense heritability of the softening rate in the nonmealy progeny was estimated by sib analysis, and the estimate was moderately high (h<jats:sup>2</jats:sup> = 0.55). A significant correlation was observed between the phenotypic value and the breeding value (twice the GCA effects) in nonmealy parents, but the phenotypic value did not significantly correlate with the breeding value in mealy parents. Therefore, contribution of a mealy parent to the softening rate of nonmealy progenies cannot be predicted by its phenotypic value.</jats:p>

Texture analysis in an apple progeny through instrumental, sensory and histological phenotyping

“…According to the Fischer coefficient, the interaction of the two factors was generally lower than the individual effect. These results agreed with the reported evolution of apple texture during storage (Holt and Schoorl 1984;Kingston 1992;Harker et al 2002;Mehinagic et al 2004Mehinagic et al , 2003Iwanami et al 2005;Camps et al 2005;Billy et al 2008), which is known to be under genetic control (Iwanami et al 2008b;Kouassi et al 2009). These changes reflected the combination of the enzymatic cell wall disassembly (Goulao and Oliveira 2008) and the loss of cell turgor pressure (Johnston et al 2002;Iwanami et al 2008a) occurring during fruit ripening.…”

“…Most parameters measured from the present progeny presented moderate to high genetic broad sense heritability for all dates and were relatively stable over storage periods. The values measured for instrumental texture variables (h 2 = 0.32-0.79) were within the range reported by Kouassi et al (2009) on 29 different apple families or Iwanami et al (2008b) on 40 families. Compression h 2 values increased between date 1 and 2, which confirmed the overall trend observed by Kouassi et al (2009).…”

“…The heritability of sensory traits was higher than those of instrumental and tended to increase with storage. They were higher (h 2 = 0.72-0.94) than those of Kouassi et al (2009); h 2 = 0.14-0.58) and (Iwanami et al 2008b; h 2 = 0.545 ± 0.194) probably resulting from the different experimental design of the sensory evaluation.…”

“…However, among the few recent quantitative genetic studies performed on apple (Durel et al 1998;Oraguzie et al 2001;Iwanami et al 2008b;Kouassi et al 2009), very seldom are those who took into account reciprocal and or maternal effects. Today most of apple breeding programs have as first objective to release scab resistant cultivars.…”

“…They have all been based on sensory tasting and global instrumental phenotyping. They led to the location of several QTLs widespread over the apple genome (King et al 2000;Iwanami et al 2008b;Costa et al 2010b;Kouassi et al 2009). In addition, few candidate genes linked to the ethylene pathway and coding cell wall acting proteins were shown to be putatively involved in the control of the trait variability (Costa et al 2005(Costa et al , 2008(Costa et al , 2010a.…”