Effect of Temperature on Symptom Expression and Reliability of Banana Streak Badnavirus Detection in Naturally Infected Plantain and Banana (Musa spp.)

Abstract

The effect of temperature on symptom expression and detection of banana streak badnavirus (BSV) by immunosorbent electronmicroscopy (ISEM) and enzyme-linked immunosorbent assay of 12 in vitro-propagated plantain hybrids (genome AAB × AA), 3 ABB cooking banana, and 3 AAB plantain landraces was studied. Experiments were done for 2 years under two temperature regimes, 28 to 35°C in a screenhouse and 22°C in a temperature-controlled room. Most BSV-infected plants of plantain hybrids expressed symptoms under both conditions. Symptom expression was enhanced when plants were continuously grown at 22°C, but later became indiscernible when plants were continuously grown at 28 to 35°C. Plants grown at 22°C and showing severe symptoms contained significantly higher virus titer than plants grown at 28 to 35°C. When asymptomatic plants with very low virus titer at 28 to 35°C were transferred back to 22°C, there was a significant increase in both symptom severity and concentration of virus (greater than 3 to 5 times) in leaf tissues after 9 months. In contrast, the concentration of virus and symptom severity decreased in plants after transfer from 22°C to 28 to 35°C. Micropropagated plants of AAB plantain landrace cv. Mimi Abue and ABB cooking bananas (cvs. Bluggoe, Cardaba, and Pelipita) did not express visible symptoms under either temperature regime, but BSV was detected by ISEM in 23% of the plants. After 2 years at 22°C, virus was detected in 64% of the plants, but the concentration of virus remained low. Implications of these results on quarantine screening of in vitro plants and virus diagnosis are discussed.

Relationship between natural occurrence of banana streak badnavirus and symptom expression, relative concentration of viral antigen, and yield characteristics of some micropropagated Musa spp.

“…Lockhart, unpublished data), suggesting that A 405 values were a reliable indication of virus titre. With a few exceptions, symptom incidence and virus indexing by ELISA were correlated; however, some symptomless plants had detectable BSV antigens (Dahal et al, 1998a(Dahal et al, , 1999a). In the current study, the incidence of BSV varied greatly between the genotypes and locations, and was significantly higher in most TMPx hybrids than in the landraces.…”

“…In Nigeria, symptom expression by BSV-infected plants was highly affected by both genotype and environment; some genotypes, such as TMPx 4698-1, TMPx 548-9 and TMPx 548-4, expressed severe symptoms during the cooler rainy season but no symptoms during the hot dry season (Dahal et al, 1998a). Even under conditions that are conducive to symptom expression, most landraces remained symptomless but virus particles were detected occasionally by ISEM (Dahal et al, 1998a). This, and the gross similarity between the symptoms caused by BSV and cucumber mosaic virus, makes symptom-based evaluation for BSV unreliable.…”

“…Some biological and molecular characteristics of an isolate (BSV-Onne) collected from this station have been described elsewhere (Harper et al, 1996;Dahal et al, 1998a;Dahal et al, 1999b;Thottappilly et al, 1998). Nigerian isolates of BSV are serologically distinct from several previously described BSV isolates (Lockhart & Olszewski, 1993) but they remain to be characterized.…”

“…Therefore BSV-infected tissue from this genotype was used as susceptible control in ELISA assays (Dahal et al, 1998a(Dahal et al, , 1999a. To determine the relative BSV antigen concentration (with respect to TMPx 4698-1) in infected tissues of the various genotypes, composite samples were used from at least five plants of each genotype.…”

“…Although many naturally occurring isolates of BSV are known to occur (B. E. L. Lockhart, unpublished data), to date isolates from Costa Rica, Honduras, Morocco, Rwanda and Trinidad have been recognized as serologically and genomically distinct (Lockhart, 1994;. Characteristics of a BSV isolate from southern Nigeria have been reported elsewhere (Dahal et al, 1998a;Thottappilly et al, 1998). The most common visual symptoms of BSV-infected plants include broken chlorotic streaks or spindle-shaped patterns on the lamina (Lockhart, 1986).…”