Archivio Journal of Plant Pathology

Abstract:

Phytophthora nicotianae, P . palmivora and P . citrophthora are the major Phytophthora species involved in citrus decline in India (Naqvi, 2006). Here we report for the first time Phytophthora lacustris (formerly P. taxon salixsoil) from India. It was isolated (isolate NRCPh112) from the rhizosphere of a citrus orchard in Sriganganagar (Rajasthan, India) in March 2011. P. lacustris was reported causing severe damages and mortality in Prunus persica orchards in Italy (Nechwatal et al., 2012). In liquid culture sporangia were non-caducous, non-papillate, ovoid to obpyriform, with an average (15 sporangia) length x breadth of 43.7x34 μm and an l/b ratio of 1.28. Internal and external proliferation of sporangia and hyphal swellings were observed, while chlamydospores were not produced. Isolate NRCPh112 induced selfing of an A1 isolate of P. nicotianae when paired on carrot agar thus functioning as ‘silent A2’ mating type while all known P. lacustris isolates from Australia, Europe and the USA are of ‘silent A1’ mating type. Colony morphology at 25±1°C was petaloid or chrysanthemum-like on V8A juice agar (Hi-Media Biosciences, India) whereas uniform wooly colonies were formed on potato dextrose agar (PDA). The average daily growth rate at 25°C on V8A, PDA and corn meal agar (CMA) was 7.9, 5.9 and 7.1 mm per day, respectively. On CMA optimum and maximum temperature for growth were around 25 and 37°C, respectively. P. lacustris has similar morphology as Phytophthora gonapodyides but was identified by sequence analysis of the ITS (accession No. JQ424900), β-tubulin (JQ520346) and translation elongation factor 1α (JQ520347) gene regions. The ITS sequence of isolate NRCPh112 showed 99% similarity with P. lacustris isolate ICMP16270 from New Zealand [JF804803; Nechwatal et al. (2012)].