Evaluation of Differences in Softening of Apple Genotypes by Linear Regression

Abstract

<jats:p>The firmness of the flesh in 27 apple <jats:italic>(Malus</jats:italic> ×<jats:italic>domestica</jats:italic> Borkh.) cultivars and selections (genotypes) was measured as an indicator of storage potential at 20 days after harvest under 20 ± 2 °C, 80% ± 5%relative humidity storage conditions. Softening ranged from 9% to 58% of initial values among genotypes after 20 days of storage. In some genotypes, softening was not continuous, a minimum firmness being reached before day 20. After a period of rapid softening, firmness declined to at least 20% of that at harvest. For each genotype, linear regression analysis of firmness changes from harvest until when firmness decreased by 20% was carried out. In genotypes in which firmness did not drop &gt;20% within 20 days of storage, the entire dates to 20 days were used for analysis. The homogeneity of the regression residual variances and their normal distribution was not rejected at <jats:italic>P</jats:italic> = 0.05, and the linear regression analysis was assumed to be applicable to the change in firmness for each genotype. Results of the regression analysis showed that the regression was significant for all genotypes except one. Therefore, storage potential could be evaluated by comparing the regression coefficient of each genotype.</jats:p>

Optimal sampling strategies for evaluating fruit softening after harvest in apple breeding

“…Since firmness does not always decrease uniformly throughout 20 days of storage, the linear regression for change in firmness was adapted from the harvest date until firmness decreased by 20%, as described by Iwanami et al (2004). When firmness did not decrease more than 20% within 20 days of storage, the data from the full length of storage (20 days) were subjected to linear regression.…”

“…Apples do not always soften continuously during storage, and the extent of softening after harvest is greatly influenced by the storage period (Iwanami et al, 2004). Determining how long it takes for fruit to become too soft for market acceptance requires regular evaluation until firmness reaches a certain value, and, consequently, many samples of fruit are required when a genotype is likely to have a long storage capability.…”

“…Therefore, although long shelf life is one of the most important objectives in apple breeding, this important part of the seedling screening is ignored in many apple-breeding programs (Alston, 1988). Recently, Iwanami et al (2004) indicated that the firmness of apple fruit significantly decreased by 20 days of storage at 20 ± 2 • C and 80 ± 5%RH even in genotypes with a long storage potential. They proposed a method to evaluate genotype differences in softening using a regression coefficient of change in firmness during storage with restricted fruit samples.…”

“…On the other hand, softening, estimated by the regression coefficient proposed by Iwanami et al (2004), is a quantitative and phenotypic expression of the softening of a genotype, which can be compared with that of another genotype, can fluctuate depending on environmental factors such as year, location, and sampling date. Johnston et al (2002) suggested that one of the major factors that influence post-harvest softening of apple fruit at harvest is their maturity.…”

Storability in Cold Temperatures Can Be Evaluated Based on Changes in Fruit Quality in Apple Genotypes Under Shelf Life Conditions

“…This means that it is difficult to evaluate the storage potential and select cultivars for their storage potential in apple breeding programs. For this reason, Iwanami et al (2004) measured changes in fruit firmness during shelf life conditions at 20°C and proposed a regression parameter that could be used as an indicator of storage potential in breeding programs. Changes in fruit quality in shelf life conditions were rapid, and cultivar differences regarding the changes could be determined shortly after harvest.…”