Poster: Diseases of Plants: Disease Detection & Diagnosis
First report of tomato late blight disease in Oman
S. Al-Kaabi (1), M. Al-Jabri (1), W. Al-Shibili (1), W. Fry (2), A. Al-Adawi (1), H. Mayton (3) (1) Ministry of Agriculture and Fisheries Sultanate of Oman, Oman; (2) Cornell University, U.S.A.; (3) Ministry of Agriculture and Fisheries Sultanate of Oman,
Prior to 2013, tomato late blight had not been reported from the Sultanate of Oman. Tomato is an important vegetable crop, with approximately 1400 ha of tomatoes in Oman. However, in 2013 a disease resembling late blight was observed in several states, with some farms reporting destruction of 100% of the area planted with tomatoes and decrease in production of 30-90% for other farms. The causal agent of late blight, Phytophthora infestans, was successfully isolated from infected plant tissues in February and March 2013. Identification of P. infestans was achieved through microscopic observation and molecular analyses. Sporangia were lemon shaped, semipapillate and caduceus ranging from 36 to 41 µm in length and 13 to 30 µm in width. Internal transcribed spacer (ITS) and cytochrome c oxidase 1 (Cox1) gene regions were amplified and sequenced. BLAST search for ITS and Cox1 sequences of isolates collected from Oman showed 100% similarity with sequences of P. infestans isolates available in genebank (NCBI). To confirm pathogencity of P. infestans in tomato, three isolates were selected to fulfill Koch's postulates. A spore suspension with concentration of 2.5 X 104 sporangia/ml of each isolate was inoculated on tomato leaves of the cultivar "Ginan" and incubated at 18 Co for 12 days. Symptoms of water soaked and greyish black lesions were observed on inoculated leaves while tomato leaves inoculated with sterile water remained healthy.