Development of isolate-specific markers for Neofusicoccum parvum and N. luteum and their use to study rainwater splash dispersal in the vineyard




Unique bands were identified in single isolates of Neofusicoccum parvum and Neofusicoccum luteum using universally primed polymerase chain reaction (UP-PCR) analysis of isolates obtained from grapevines and non-grapevine hosts in New Zealand, Australia, South Africa and the USA. Primers were designed to amplify a 1550 bp portion of the 1573 bp marker band from N. parvum isolate B2141 and a 510 bp portion of the 524 bp marker band from N. luteum isolate G51a2. A PCR-RFLP assay was developed to distinguish the N. parvum isolate B2141 from other N. parvum isolates, based on a polymorphism found in the marker band using the TaqI restriction endonuclease. For N. luteum isolate G51a2, the designed primers were specific at an annealing temperature of 63°C in the PCR. The sensitivity threshold of the N. parvum and N. luteum isolate-specific markers was 50 pg and 5 pg, respectively, when used in standard PCR with purified genomic DNA. The sensitivity of the N. parvum isolate-specific marker was increased to 0·5 pg by nested PCR. The specificity test of both isolate-specific markers with six other Botryosphaeriaceae spp. showed that they were specific to their respective species and isolates. Both markers were able to detect the conidia of N. parvum and N. luteum marker isolates in rainwater samples collected at different distances from an inoculation point in the vineyard. The results showed that rain splash could disperse the conidia of both of these species up to 2 m from the inoculum point in a single rainfall event.