An efficient assay for detection of Phytophthora cinnamomi in the rhizosphere of Sweet Chestnut (Castanea sativa Mill.)

Abstract

The life cycle of Phytophthora cinnamomi Rands and P. cambivora (Petri)Buisman, both species associated with Ink Disease of Chestnut, occurs entirely in soil. The presence of any of these parasitic species is a limiting constraint for new plantations of sweet chestnut and represents a serious problem for established groves. Sensitive and fast detection methods are necessary to guarantee the absence of inoculum in the propagation material and to evaluate the sanitary condition of soils. In this study a method that involved a baiting assay conjugated with selective agar medium was developed. As biological baits, leaf discs of sweet chestnut (Castanea sativa), holly trees (Ilex aquifolium) and camellia (Camellia japonica) were used, at 25 ºC and normal laboratory conditions with or without addition of biocides (pimaricin and penicillin) in the water of soil dilution. The leaf discs of sweet chestnut were more efficient for detection of Phytophthora and greater percentage of positive isolations were always obtained in the selective medium P10VPH. Results of this study allow us to establish an efficient protocol for detection of P. cinnamomi associated with Ink Disease of Chestnut in the rhizosphere of sweet chestnut.