APS Homepage

Poster: Diseases of Plants: Disease Detection & Diagnosis


Identification of Alternaria species associated with tomato and potato early blight disease in Oman
H. MAYTON (1), A. Al-Rubaii (2), S. Al-Kaabi (2), M. Al-Jabri (2), R. Al-Maqbali (2), A. Al-Adawi (2) (1) Ministry of Agriculture and Fisheries Sultanate of Oman, Cornell University, Oman; (2) Ministry of Agriculture and Fisheries Sultanate of Oman, Oman

In Oman, approximately 1400 hectares of tomatoes are planted each year with an annual production that exceeds 74000 tons. Tomatoes are ranked as the most important vegetable crop grown by local farmers. Early blight is a devastating disease in Oman and affects both tomato and potato production. In order to manage the disease more effectively, the Ministry of Agriculture and Fisheries in Oman initiated a project to characterize the pathogen population. Samples were collected from infected tomato and potato plants in commercial production fields during the 2014 and 2015 growing seasons from states in the north and south Al-Batinah governates in Oman. Alternaria spp. were isolated from symptomatic tissues. Microscopic examination of cultures from single spore isolations revealed three distinct species: Alternaria tenuissima, A, alternata and A. solani. Molecular identification was achieved through amplification and sequencing of internal transcribed spacer (ITS) and histone 3 gene regions. Phylogenetic analysis of the ITS gene clearly separated Alternaria solani from the other two species. Partial coding of histone 3 gene revealed three clades representing A. alternata (440bp), A. solani (489bp) and A. tennusima (546bp). Pathogenicity tests of the sample isolates on detached tomato leaves of cultivar ‘Ginan’ showed brown lesions similar to symptoms observed in field. No symptoms were observed in water-inoculated control tomato leaves.