The identity, distribution and diversity of botryosphaeriaceous species in New Zealand vineyards – a national perspective

Abstract

In recent years molecular tools have been applied to provide understanding of the population structures of botryosphaeriaceous species in New Zealand vineyards. A national survey of symptomatic material from 43 vineyards showed that 88% had infection by botryosphaeriaceous species. Vine age had the strongest correlation with incidence, with the least infection in grapevines 1–5 years old (30%). Sequencing of taxonomic genes identified nine species. In contrast to other countries, N. luteum and N. parvum were predominant species with Lasiodiplodia theobromae notably absent. As with other countries, research showed that distribution is likely to be related to climate. Analysis of populations demonstrated that, despite predominantly asexual reproduction, the genetic diversity of isolates within species was high. Frequent hyphal anastomoses and fusions were observed in dual culture with weak vegetative compatibility barriers. This indicated the likelihood of frequent parasexual recombination. The isolation of genetically similar isolates from single lesions reinforced this hypothesis. A suite of molecular tools were developed to aid epidemiology studies. Endogenous markers produced for isolates with typical pathogenesis showed they could be dispersed at least 2 m from the site of conidiation in a single rain/wind event. The use of a multi-genus PCR-SCP system showed that N. parvum and N. luteum are released year round and this probably contributes to their successful invasion of vineyards. Application of these molecular tools has provided a comprehensive snapshot of New Zealand vineyards revealing a thriving and diverse population of botryosphaeriaceous species that present a serious concern to the industry.