STUDIES ON A NIGERIAN ISOLATE OF BANANA STREAK BADNAVIRUS - II - EFFECT OF INTRAPLANT VARIATION ON VIRUS ACCUMULATION AND RELIABILITY OF DIAGNOSIS BY ELISA

Monitoring of banana streak badnavirus (BSV) antigens and symptoms in naturally BSV-infected plantain and banana (Musa spp.) plants showed a great variation in symptom expression, distribution and relative conc entration of BSV between and within plants. Expression and distributio n of symptoms was erratic within individual leaves as well as between different leaves of the same plant. The concentration of BSV antigens detected by triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) varied in different plant parts including leaf lamina, mi drib and pseudostem, roots and young 'cigar' leaf. The concentration o f BSV antigens was high in symptomatic tissues but was low or below th e limits of detection in most asymptomatic tissues. During 'hot dry' s easons when symptoms were not fully expressed, the concentration of BS V antigens in leaf tissues declined drastically, often below the detec tion Limit of TAS-ELISA. These results suggested that for more reliabl e detection of BSV antigens by TAS-ELISA, it is advisable to index pla nts using composite tissue samples comprising as many leaves as possib le for each plant and collected during cool and/or rainy seasons when symptom expression is generally severe.