The pathogenicity of Cylindrocarpon destructans, a factor in grapevine decline and its potential management using composted soil amendments

Grapevine decline in Pennsylvania has been attributed to a number of biotic and abiotic factors that vary depending on vineyard site and management practices employed. In 1999 several fungi were isolated and identified from the roots of grapevines exhibiting symptoms of decline including reduced shoot growth, sparse chlorotic foliage, reduced yield and necrosis and stunting of the roots. Cylindrocarpon destructans (Zinssmeister) Scholten, one of the fungi identified, has been associated with grapevine decline in many of the wine grape growing regions of the world including California, Italy, France, Portugal, South Africa, Australia and New Zealand. Research studies on a wide array of hosts have characterized the host-fungus relationship along a continuum from a virulent pathogen to a stress-induced weak pathogen to a saprophyte. The objective of this research was to identify where an isolate of C. destructans from Pennsylvania fits along this continuum. The results of this study indicate that C. destructans may be characterized as an endophyte due to its ability to infect and colonize the roots of grapevine cv. Vidal and rootstock Coudrec 3309 under a variety of greenhouse and field conditions without producing any visible symptoms or signs. However, its potential role as a latent stress-induced pathogen can not be dismissed.; The strategies available to growers to help manage soil-borne fungi are limited. Research over the past several decades has demonstrated that applying composted soil amendments to agricultural land has many benefits ranging from improved soil structure and water drainage to the suppression of soil-borne fungal plant pathogens. The objective of the second part of this research was to evaluate the suppressiveness of several types of composted soil amendments on C. destructans. Although, C. destructans was able to infect and colonize rooted Vidal cuttings grown in soil-less media amended with various types of compost, several bacteria were isolated from the various composted soil amendments and were antagonistic towards C. destructans in vitro.