Effect of grapevine rupestris stem pitting-associated virus on the agronomical and physiological perforrmances of a clone of "Bosco" (Vitis vinifera L.)

Grapevine rupestris stem pitting-associated virus (GRSPaV) is a widely spread virus affecting Vitis spp. Although it established a compatible viral interaction in Vitis vinifera L. without the development of phenotypic alterations, it can occur as distinct variants that showed different symptoms on diverse Vitis species. We investigated changes induced by GRSPaV on agronomic and physiological performances of V. vinifera cv. Bosco, an Italian white-grape variety. We compared the behaviour in the field of two lines, grafted onto 1103 P rootstock, of the same clone of Bosco, one GRSPaV-infected and one GRSPaV-free. In three consecutive years (2010-2012), bunch and berry biometric data, agronomic performances and juice composition were assessed at the harvest time. Likewise, the main physiological parameters, i.e. photosynthetic rate, transpiration rate, stomatal conductance, sub-stomatal CO2 concentration and leaf chlorophyll content of vines were measured in different dates during 2010 and 2011. The presence of the virus caused a moderate decrease of physiological efficiency and of juice soluble solids content as well as an increase of juice acidity. The most evident effect of the virus infection, however, was exerted on the biometric characteristics of berries which all resulted clearly reduced. The results suggest that also the GRSPaV, commonly reputed irrelevant for the absence of symptoms on Vitis vinifera, may induce changes on vine behaviour.