VARIABILITY IN SORBITOL - SUCROSE RATIO IN MATURE LEAVES OF DIFFERENTPRUNUS SPECIES

Sorbitol is a sugar alcohol, present with sucrose in Rosaceae trees, w hich seems to have a role in plant response to environmental stress. T he aim of this study was to investigate variability in sorbitol : sucr ose ratio in source leaves of 53 species or hybrids of Prunus. The stu died taxa, representing three subgenera and 11 sections of the Prunus genus, were chosen from the Prunus collection at the Institut National de la Recherche Agronomique, Bordeaux, France. Young mature leaves we re sampled on three dates in spring and summer and were analyzed for n eutral soluble sugars using highperformance liquid chromatography. The re were differences in sorbitol : sucrose ratio according to sampling date and according to taxon, Sorbitol content increased and sucrose co ntent decreased from May to July, leading to an increase in sorbitol : sucrose ratio, For each date, there was a high variability within bot anical sections for sorbitol : sucrose ratio, The highest variability between species for sorbitol : sucrose ratio was in July, with P. coco milia having the lowest ratio (1.15, w/w) and P. fremontii having the highest ratio (5.59, w/w). When species were pooled according to their geographical zone of origin, species originating from Japan showed th e lowest sorbitol : sucrose ratio for all sampling dates, In July, spe cies originating from Japan, Europe, and central to western North Amer ica had sorbitol : sucrose ratio significantly lower than that of spec ies originating from Europe to western Asia, China to eastern Asia, an d central to eastern North America. These results indicate that variab ility in sorbitol : sucrose ratio exists in the Prunus germplasm and s eems to be related to the geographical origin of the species. Moreover , variability in sorbitol to sucrose ratio is high in the germplasm of different Prunus taxa.