Virulence affected by assay parameters during grapevine pathogenicity studies with Botryosphaeriaceae nursery isolates

Abstract

This study assessed the symptoms that developed when 114 Botryosphaeriaceae isolates from grapevine nursery plant materials were used to inoculate excised green shoots and 1-year-old rooted canes of Sauvignon blanc. The experiments showed that all isolates and species were able to produce lesions. Overall, the Neofusicoccum species were shown to be highly pathogenic in both tissue types while the Diplodia species were highly pathogenic on canes but not on green shoots. Isolates of the most prevalent species, N. luteum and N. parvum, showed varying lesion lengths on excised green shoots and canes. An evaluation of the factors associated with lengths of lesions showed that they were significantly affected by experimental batch which reflected inherent host and environmental factors over time. Reisolation from inoculated canes also indicated that most isolates of all species except D. seriata were able to spread internally beyond the lesions. Genetic variability analysis using UP-PCR showed that N. luteum isolates were genetically diverse but no association was observed between the phylogenetic group and degree of pathogenicity caused by the isolates. This study demonstrated that all Botryosphaeriaceae species from grapevine nurseries were pathogenic to grapevines and that the lesion lengths varied between species, among isolates within a species and among nursery sources, and was affected by the test method.

High genetic and virulence diversity detected in Neofusicoccum luteum and N. australe populations in New Zealand vineyards

“…Billones‐Baaijens et al . () showed that N. luteum was the predominant pathogen (57%) in nursery cuttings in New Zealand. The nursery industry in New Zealand is small, and relatively few nurseries are responsible for production and distribution of large amounts of new planting material.…”

“…In contrast, Billones‐Baaijens et al . () found N. australe to comprise only 8% of infections in nursery material. In contrast to N. luteum , only 42% of the N. australe isolates clustered within group 1.…”

“…This study also reported that the isolates of N. parvum had greater homogeneity between vineyards and regions, while Botryosphaeria dothidea showed homogeneity between regions. Genetic and virulence variability studies of N. parvum populations from New Zealand vineyards and N. luteum population from nurseries have reported high levels of genetic variability among isolates of both species (Baskarathevan et al, 2012b;Billones-Baaijens et al, 2013b). However, these studies found no correlation between genetic groups and virulence within N. luteum and N. parvum populations.…”

“…Pathogenicity studies have reported variations in virulence among isolates within N. luteum and N. australe species (van Niekerk et al, 2004;Amponsah et al, 2011;Billones-Baaijens et al, 2013b). Genetic differences within a species population may contribute to intraspecies virulence variation.…”

“…Various DNA fingerprinting methods have been used to study the population structure of Botryospheriaceae species, including: random amplified polymorphic DNA (Smith et al, 2000), inter-simple sequence repeats (Qiu et al, 2015), microsatellites (Burgess et al, 2003) and universally primed PCR (UP-PCR) (Baskarathevan et al, 2012b;Billones-Baaijens et al, 2013b). UP-PCR is a simple method that can amplify DNA from any organism without any previous knowledge of the DNA sequences.…”