Sorbitol is a sugar alcohol, present with sucrose in Rosaceae trees, which seems to have a role in plant response to environmental stress. The aim of this study was to investigate variability in sorbitol : sucrose ratio in source leaves of 53 species or hybrids of Prunus. The studied 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 were sampled on three dates in spring and summer and were analyzed for neutral soluble sugars using high-performance liquid chromatography. There were differences in sorbitol : sucrose ratio according to sampling date and according to taxon. Sorbitol content increased and sucrose content decreased from May to July, leading to an increase in sorbitol : sucrose ratio. For each date, there was a high variability within botanical sections for sorbitol : sucrose ratio. The highest variability between species for sorbitol : sucrose ratio was in July, with P. cocomilia 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 the lowest sorbitol : sucrose ratio for all sampling dates. In July, species originating from Japan, Europe, and central to western North America had sorbitol : sucrose ratio significantly lower than that of species originating from Europe to western Asia, China to eastern Asia, and central to eastern North America. These results indicate that variability in sorbitol : sucrose ratio exists in the Prunus germplasm and seems 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.
Annick Moing, Nathalie Langlois, Laurence Svanella, Anne Zanetto, and Jean-Pierre Gaudillère
Annick Moing, Christel Renaud, Hélène Christmann, Lydie Fouilhaux, Yves Tauzin, Anne Zanetto, Monique Gaudillère, Frédéric Laigret, and Jacques Claverie
Rain-induced fruit cracking is a limiting factor for sweet cherry (Prunus avium L.) growers in many production areas. Although many studies have concerned this complex phenomenon, the basic mechanisms involved in fruit cracking remain unclear. We re-examined the relations between osmotic potential and cracking susceptibility in cherry fruit by comparing the osmotic contribution of the major metabolites separately in flesh and skin, in four cultivars (with different levels of susceptibility to cracking) at four stages of development. Several differences were observed between flesh and skin revealing compositional gradients in the fruit tissues. Acidity and malate concentrations were higher in flesh than in skin for all stages. The absolute value of osmotic potential was higher but the contribution of the sum of sugars to osmotic potential was lower in flesh than in skin. As determined using fruit immersion test, `Fermina' and `Regina' were less susceptible to fruit cracking than `Lapins' and `Brooks'. At commercial maturity when fruit susceptibility to cracking was highest, no clear difference appeared between `Brooks' and `Lapins' compared to `Regina' and `Fermina' for flesh or skin osmolarity and for the contribution of the major sugars or organic acids to skin and flesh osmotic potential.