Fruit quality of Sicilian, commercially affirmed, and newly selected apple varieties: potential resources for genetic improvement and specialty markets

Several apple varieties are constantly selected for improved quality traits and introduced for cultivation and marketing in addition to a few traditional and affirmed varieties. Recently, specific fruit quality traits like enhanced flavor, crispness and juiciness have been particularly requested by consumers and are gradually replacing more conventional characteristics like fruit size, peel color and sweetness in the breeding programs. Furthermore, some of the newly selected varieties exhibit a relatively low level of plasticity, posing serious problems of adaptation when cultivation is proposed in a wide range of environments. In this most recent perspective, some of the old varieties or local genotypes may assume relevant importance as a source of genetic material or may even find space in the renewed concept of apple fruit consumption and for diffusion in new areas of cultivation. Starting in 1999, a collection of apple varieties including several local Sicilian genotypes as well as newly selected cultivars obtained by different international breeding programs has been established in Central Sicily. Fruit quality evaluation has been carried out for several years on local genotypes as well as on commercially affirmed varieties, and constantly compared to those of the improved cultivars, which are introduced every year. In addition to agronomical responses, phenological behavior, and disease resistance, fruit physical, chemical and sensory analyses have been carried out on several genotypes and cultivars, and produced a large dataset which was used to establish the fruit quality value and potential of local genotypes relative to commercially affirmed and newly selected varieties. Specifically, a multivariate approach was used to compare the three groups of varieties, establish associations with specific quality traits and determine their relative value in terms of overall fruit quality. A linear function including six parameters, namely flesh firmness, titratable acidity, peel color index, fruity odor, acid taste, grassy flavor, was able to discriminate entirely the three groups of cultivars. Principal component analysis revealed some expected associations like the one between acidity or acid taste and grassy flavor, and some other interesting relationships, like the association between honey flavor, almond flavor and flesh firmness. But most importantly, cluster analysis on standardized components scores allowed for the individuation of four main groups associating specific quality parameters with certain cultivars. In particular, two of the most popular commercial varieties (Fuji and Golden Delicious) were distinguished for juiciness and apple/fruity odor/flavor and grouped together with two local genotypes, Bommino and Turco. Other two local genotypes were distinguishable for enhanced honey and almond flavors/odors, sweet taste and high flesh firmness. On the contrary, most of the new selections were grouped together and associated to enhanced fruit size, soluble solids and percent of cover color. This comprehensive evaluation basically indicated that some of the minor local varieties may in fact carry specific quality traits of great interest and should be further explored for their inclusion in breeding programs or proposed on the market as specialty products with well defined characteristics.