First Report of Citrus tristeza virus (CTV) Disease in Commercial Citrus Orchards in Sudan

Abstract

Three extensive surveys and laboratory tests were conducted to detect and determine the distribution of Citrus tristeza closterovirus (CTV) in the main citrus groves in six states along the Blue Nile (Gezira and Sinnar states) and the River Nile (Khartoum, River Nile, and Northern states) in addition to Kassala state in eastern Sudan. Citrus tristeza virus was detected as an emerging disease of citrus for the first time in Sudan based on visual external symptoms on foliage and fruits and on characteristic internal symptoms on bark and wood at the bud union region of affected citrus trees. The occurrence of CTV was confirmed by direct tissue blot immunoassay (DTBIA) and DAS ELIASA serological tests. It was naturally prevalent in all the surveyed areas infecting grapefruit, orange, lime and mandarin revealing an overall incidence of 37%. Tristeza was found to be more widely spread (45-65%) in the states along the River Nile compared to those along the Blue Nile and in the east (10-30%). In comparison, DTBIA with monoclonal antibodies 3DF1+3CA5 was more efficient in detecting CTV than DAS-ELISA which was only successfully detecting the virus in few fresh samples but not from dried citrus samples.