RT-PCR detection of seedborne Cowpea aphid-borne mosaic virus in peanut

The Brazilian strain of Cowpea aphid-borne mosaic virus (CABMV) is a severe pathogen in peanut and a significant problem when distributing germ plasm to other countries. The virus is seedborne at approximately 0.15% in peanut, depending upon the cultivar, and its detection in seed lots would strengthen quarantine programs. Utilizing 3' sequence data (GenBank Accession #AF241233), primers were designed from the coat protein region and evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Use of the forward primer 5'-CGCTCAAACCCATTGTAGAA-3' and reverse primer 5'-TATTGCTTCCCTTGCTCTTTC-3' yielded a 221-bp product. Extracts of thick seed slices and a sample size of 12 to 25 seed showed no significant advantage of RT-PCR over enzyme-linked immunosorbent assay (ELISA) in tests of large seed lots. However, RT-PCR detected more virus in seed than in the number of infected seedlings normally arising in germination tests. Also, RT-PCR was extremely sensitive and detected 1 infected leaf among 99 healthy leaves. In contrast, ELISA detected only one infected leaf among nine healthy leaves.