VARIABILITY IN SORBITOL - SUCROSE RATIOS IN MATURE LEAVES OF DIFFERENT PEACH CULTIVARS

The aim of this study was to investigate variability in the sorbitol : sucrose ratio (SSR) in source leaves of different peach [Prunus persi ca (L.) Batsch] cultivars. Four- and 5-year-old trees of 58 cultivars were examined. Mature leaves were sampled on three dates in middle to late summer and analyzed for neutral soluble sugars using high-perform ance liquid chromatography. Differences in SSRs were observed. In most cultivars, the sorbitol content was at least twice that of sucrose. T he maximal range of SSR occurred on the third date and ranged from 1.5 to 4.3. There was a date x genotype interaction (P < 0.01). When cult ivars were grouped by country of origin, the mean ratios of the Japane se group were lower than those Of the Italian and American groups for all three sampling dates. The SSRs bf nectarines were higher than thos e of peach and canning clingstone-type cultivars. In general, variatio ns in SSR were due mostly to differences in sucrose content. The SSR w as negatively correlated with flowering date. These results indicate v ariability in SSR in peach germplasm, variability that seems to be rel ated to the geographical origin of the cultivars.