Studies on a Nigerian isolate of banana streak badnavirus. I. Purification and enzyme-linked immunosorbent assay

Summary A Nigerian isolate of banana streak badnavirus (BSV) was purified and a polyclonal antiserum was produced in mice. The antiserum titre was between 1:10 000 and 1:40 000 in enzyme linked immunosorbent assay (ELISA), and showed a good specificity to BSV antigens. Comparative tests were carried out to determine the sensitivity and reliability of BSV antigen detection by double antibody sandwich (DAS)‐ELISA, triple antibody sandwich (TAS)‐ELISA, antigen coated plate (ACP)‐ELISA, and protein‐A coated antibody sandwich (PAS)‐ELISA. TAS‐ELISA using rabbit polyclonal antiserum to trap BSV and mouse polyclonal antiserum to detect the virus particles, was more sensitive than ACP‐ELISA and PAS‐ELISA and detected BSV in plant extracts from both symptomatic and some asymptomatic plants. However, immunosorbent electron microscopy detected more BSV‐infected plants from asymptomatic plant samples than did TAS‐ELISA. Results of this study showed that detection of BSV antigens in sap extracts by TAS‐ELISA was most efficient with symptomatic tissues which occurred most frequently in the ‘cool rainy’ season. This suggests that for more reliable BSV‐indexing of field samples, tissue sampling should be done during the rainy season when most BSV‐infected plants express severe symptoms.