APS Homepage

Poster: Diseases of Plants: Disease Detection & Diagnosis


First report of Watermelon chlorotic stunt virus in rain-fed farms in Usfan, Saudi Arabia
N. CHINGANDU (1), M. Al-Saleh (2), A Idris (3), J. Brown (1); (1) University of Arizona, Tucson, AZ, U.S.A.; (2) Department of Plant Protection, King Saud University, Saudi Arabia; (3) University of Arizona, School of Plant Sciences, Tucson, AZ, U.S.A.

Watermelon (Citrullus vulgaris L.), an important crop in Saudi Arabia, is cultivated in the lowlands and wadis following seasonal winter rainfall, along the western coast. Production of watermelon faces constraints imposed by abiotic stresses and biotic diseases, and insects, including whiteflies. During spring 2015, >95% of watermelon plants growing on a farm near Usfan exhibited foliar chlorosis and mottling, and overall stunting symptoms, reminiscent of those caused by Watermelon chlorotic stunt virus (WmCSV) (Begomovirus, Gemniviridae). Total nucleic acids were isolated from leaves of three symptomatic watermelon plants, and subjected to rolling circle amplification (RCA). Libraries prepared for the RCA amplicons were subjected to Illumina MiSeq, and reads were assembled using SeqMan NGen software. BLASTn analysis of assembled contigs revealed the presence of the DNA-A and DNA-B genomic components most closely related to the Old World bipartite WmCSV. The three DNA-A components, at 2752 bp, shared 99-100% nucleotide (nt) identity with each other, and 99% nt with a WmCSV isolate from Leith, Saudi Arabia [KJ939448]. The three DNA-B component sequences, at 2757 bp, shared 96-97% nt identity with each other, and 96% nt identity with the DNA-B component of an isolate, also from Leith [KJ939447]. This is the first report of WmCSV in the Leith, a farming community separated from Usfan by a vast, inhospitable desert.