First Report of Potato spindle tuber viroid in Tomato in New Zealand

During May 2000, symptoms resembling those of Potato spindle tuber viroid (PSTVd) infection were observed in glasshouse tomatoes (cv. Daniella) growing on one site in Tuakau, South Auckland, New Zealand. Symptoms appeared 2 to 3 months after planting, were confined to plant tops, and included leaf interveinal chlorosis, epinasty, and brittleness. Affected plants comprised ≍10% of the crop and were located near access points. PSTVd was identified in symptomatic plants by the Dutch Plant Protection Service and confirmed by mechanical transmission and grafting to tomato cv. Rutgers and reverse transcription polymerase chain reaction (2). The sequenced genome of this isolate (Accession AF369530) was 358 nt in length and had the closest homology to a Dutch isolate (Accession X17268). Electron microscopy did not reveal the presence of any viruses in affected plants and specific tests for other tomato pathogens were negative. A survey of 50 tomato glasshouse facilities throughout New Zealand revealed three further infected sites, two located close to the original site and one in Nelson, some 480 km distant. However, a survey of field-grown potato crops within 1.5 km of the original outbreak site did not reveal the presence of the viroid. PSTVd is seed transmitted and was probably introduced in glasshouses by use of infected seed. Glasshouse tomatoes are an important crop in New Zealand and annual production is currently 40,000 tonnes. The yield of affected plants may be decreased by up to 80% if suitable controls are not implemented (1). References: (1) S. Kryczynski et al. Phytopath. Polonica 22:85, 1995. (2) A. M. Shamloul et al. Can. J. Plant Pathol. 19:89, 1997.