Incidence and distribution of Citrus tristeza virus in citrus cultivars in Ibadan, southwest Nigeria

Abstract: A survey was conducted on a 33 year old orchard to determine the incidence and distribution of Citrus tristeza virus (CTV), genus Closterovirus in different citrus cultivars at National Horticultural Research Institute (NIHORT), Ibadan, Nigeria. Compound enzyme-linked immunosorbent assay (Compound ELISA) was used to detect the presence of CTV in the citrus leaf samples. The results revealed 100% incidence in all the varieties tested. Of all the sweet oranges (Citrus sinensis) budded on Cleopatra mandarin rootstock, Washington Navel had the least plant survival of 2 out of the 12 planted with a canopy spread of 7.91 m and fruit yield of 7.00 kg per tree. It also had the highest mean ELISA reading with an absorbance (A₄₀₅nm) of 3.4780 while Bende had the least titre of 3.2158 with plant survival of 12 out of the 12 trees planted and fruit yield of 57.70 kg per tree. No significant difference was observed in Agege variety of sweet orange budded on different rootstock types and their ELISA values ranged from 3.283 to 3.384. Among the seedling trees, White grape recorded the highest mean ELISA value of 3.4698 while the average ELISA values of the other seedling trees were not statistically different from each other with their titres ranging between 3.2712 and 3.3615. The results establish the pandemic status of CTV in NIHORT orchard. The use of resistant cultivars and cross protection are recommended as effective, economical and environment-friendly means of preventing the incidence and spread of CTV.