Genetic analysis of Neofusicoccum parvum and N. luteum isolates from nurseries and vineyards indicates different infection sources

Abstract

Surveys in 2007-08 showed that Neofusicoccum parvum and N. luteum are the two most prevalent and virulent species found in New Zealand vineyards and nurseries. However, N. parvum is more common in vineyards while N. luteum dominates in nurseries. Pathogenicity studies also showed that N. parvum was more aggressive and produced more severe, darker external lesions on canes than N. luteum. This study used genetic data to elucidate population origins of N. parvum and N. luteum from vineyards and nurseries. Vineyard and nursery isolates of N. parvum (n=79) and N. luteum (n=64) were genotyped using five universally-primed polymerase chain reaction {UP-PCR) primers. The five primers were able to amplify a total of 51 loci for N. parvum (66% polymorphic) and 54 loci for N. luteum {44% polymorphic). Phylogenetic analysis using parsimony (PAUP) showed that 92% and 78% of the N. parvum and N. luteum populations, respectively, were of unique genotypes. The neighbour joining trees showed that N. parvum from nurseries clustered separately from the vineyard isolates indicating the two populations were genetically distinct. This supported the initial hypothesis that the nursery infections by this aggressive species were intercepted during the grading process and, therefore, there was less movement of this species to the vineyards. In contrast, the N. luteum nursery and vineyard populations showed high genetic similarities. This indicated that the less distinct symptoms caused by this species are not graded out and, therefore, these infections can easily migrate from the nurseries to the vineyards .