Viruses Genomes - BANANA BUNCHY TOP VIRUS

Banana bunchy top virus (BBTV) is the pathogen which causes banana bunchy top disease of bananas. It is transmitted by the aphid vector, Pentalonia nigronervosa and is considered to be the most economically destructive of the virus diseases affecting bananas worldwide. (Bananas are the fourth largest fruit crop in the world, after grapes, citrus fruits and apples.)

BBTV is one of the most serious diseases of banana. Once established, it is extremely difficult to eradicate or manage. BBTV is widespread in Southeast Asia, the Philippines, Taiwan, most of the South Pacific islands, and parts of India and Africa. In Hawaii, BBTV was first observed in 1989 and is now widely established and a huge threat to the Hawaiian banana industry.

The virus is spread from plant to plant by aphids and from place to place by people transporting planting materials obtained from infected plants. Some banana varieties, like the Cavendish types, are more readily infected with the virus, but no variety of banana is resistant. Banana plants that show symptoms rarely bear fruit, and because they are reservoirs of the virus, they must be destroyed.

The initial symptoms of BBTV consist of dark green streaks in the veins of lower portions of the leaf midrib and the leaf stem Also, dark green, hook-like extensions of the leaf lamina veins can be seen in the narrow, light-green zone between the midrib and the lamina. On mature plants infected with BBTV, new leaves emerge with difficulty, are narrower than normal, are wavy rather than flat, and have yellow (chlorotic) leaf margins. They appear to be “bunched” at the top of the plant, the symptom for which this disease is named. Severely infected banana plants usually will not fruit, but if fruit is produced, the banana hands and fingers are likely to be distorted and twisted.

Banana bunchy top virus is spread by the banana aphid, which acquires the virus after at least four (but usually about 18) hours of feeding on an infected plant. The aphid can retain the virus through its adult life, for a period of 15–20 days. During this time, the aphid can transmit the virus to a healthy banana plant by feeding on it.

There is no cure for BBTV. Aphid control with pesticides is the only solution to control the virus and sequencing of the complete genome will allow researchers to try to develop BBTV resistant banana varieties.

References:

http://www2.ctahr.hawaii.edu/oc/freepubs/pdf/PD-12.pdf http://www.issg.org/database/species/ecology.asp?si=141&fr=1&sts