Variation in Symptom Development and Infectivity of the Banana Bunchy top disease on four varieties of Musa sp.

Abstract Banana bunchy top disease (BBTD), is a viral disease of banana, rapidly spreading in Africa. It affects production and seed systems, threatening the genetic diversity of banana and plantain. Early symptomatic detection and roguing are an effective way of managing this disease. However seasonal and cultivar variation in disease expression has been observed. We therefore sought to assess the relationship between symptom expression and infectivity of diseased plants to support refining roguing protocols. Plantlets from four varieties (FHIA 25; Aloga; Ebenga and Sotoumon) were inoculated using infected aphids and monitored for nineteen weeks. The plants were also used as inoculum sources to infect clean banana aphids that were transferred to healthy plants of a single variety every two weeks. An appearance of symptom in these test plants was recorded and infection tested by PCR. The hybrid FHIA 25 showed typical BBTD symptoms three weeks after inoculation, while the plantains Aloga and Ebenga showed the morse code symptom, on the leaf lamina but not on the petiole, four weeks after inoculation. The banana local variety, Sotoumon, only showed the first symptoms fifteen weeks later, and entirely missed the earlier typical symptoms. For all varieties, BBTV was only detectable and aphid transferable from plants showing the first symptoms. Overall, FHIA 25 was the most sensitive while the local banana Sotoumon the least sensitive to BBTV inoculation. The expression and spread of BBTD could be tested in the field. We discuss the implication of these observations on seed systems production losses.