Ashis K. Das

Unigene-Derived Microsatellite Marker Based Variation Study of Phytophthora nicotianae Isolates Infecting Citrus

Unigene sequence in public database provides a cost-effective and valuable source, for the development of microsatellite markers also known as unigene-derived microsatellite (UGMS) markers. In our study, genetic variation among 24 Phytophthora nicotianae isolates from five major citrus growing states of India were analysed through UGMS markers. Morphological and clustering results indicated variation among these Phytophthora nicotianae were independent of its geographical confinement and showed 62.27% polymorphism. The study also validated the potential use of UGMS markers.

First report of Phytophthora insolita in India.

During the 2010 monsoon season, Phytophthora insolita was isolated from water accumulated under the canopy of a Nagpur mandarin tree (Citrus reticulata) in Nagpur, Maharashtra State, India. The identity of the isolate was confirmed by morphological and molecular methods. This is the first report of P. insolita from India.

Morphological and Molecular Description of Phytophthora insolita Isolated from Citrus Orchard in India

Citrus, an important cash crop in India, is adversely affected by Phytophthora nicotianae, P. palmivora, and P. citrophthora. Phytophthora insolita is known to be associated with citrus and reported for the first time in India. It is a rare and poorly characterized Phytophthora species, as its natural host and pathogenic impact are unclear. Previously, it was reported only in Taiwan and China; so to confirm our suspected isolate is P. insolita, regions of internal transcribed spacer, elongation factor, beta-tubulin, and cytochrome oxidase genes were sequenced. This study provides description of the lone Indian P. insolita isolate with respect to molecular identity, morphology, mating behaviour, and pathogenicity.

First report of an atypical strain of Phytophthora inundata causing Kinnow mandarin decline in India

Abstract Kinnow mandarin is an important commercial fruit crop in India. A Phytophthora species was recovered from rhizosphere soil of declining Kinnow mandarin trees at Abohar area, Punjab state, India in January 2015. Morphological and physiological characteristics coupled with ITS-RFLP and sequence analysis of the ITS and cox1 gene regions revealed the isolate was an atypical strain of P. inundata. The isolate had ovoid to limoniform non-papillate sporangia and produced thick-walled, spherical oogonia with amphigynous antheridia. Thin-walled chlamydospores or hyphal swellings with radiating hyphae were formed readily in water in greater abundance than sporangia. This atypical strain of P. inundata was heterothallic (A1 mating type) and grew very slowly at 35°C. The optimum temperature for growth was 25°C and the isolate was metalaxyl-sensitive. Pathogenicity tests indicated that the strain of P. inundata has the potential to infect leaves and stems of Kinnow mandarin and was also pathogenic to rough lemon rootstock seedlings, causing root rot and decline. To our knowledge, this is the first report of P. inundata in India.