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

• Published in: Canadian journal of plant pathology Vol. 39; no. 3; pp. 365 - 372
• Main Authors: Das, Ashis K., Nerkar, Sagar, Thakre, Neha, Kumar, Ashok
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 03.07.2017; Taylor & Francis Ltd
• Subjects: Abundance; Chlamydospores; Citrus nobilis Lour × C. deliciosa Tenora; Hyphae; ITS-RFLP; Leaves; Mating; Metalaxyl; Oogonia; Pathogenicity; Pathogens; Physical characteristics; Phytophthora inundata; RFLP de l'ITS; Rhizosphere; Root rot; rough lemon; Seedlings; Sporangia; Stems; India
• ISSN: 0706-0661; 1715-2992
• DOI: 10.1080/07060661.2017.1364296

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.