Source: Fresh Plaza [summ. Mod.DHA, edited]
In Africa, banana bunchy top disease was first identified in the 1960s in the Democratic Republic of Congo. It has since been spreading through planting material and banana aphids. Currently, it is thought to be present in up to 16 countries on the continent [e.g., ProMED post 20211012.8699013]. The virus is also endangering the diversity of banana varieties and landraces well-adapted to local conditions, which are grown by farmers.
The Consultative Group for International Agricultural Research (CGIAR) through its International Institute of Tropical Agriculture (IITA), together with a number of international research institutions and stakeholders, have established an alliance to address the issue in the region and develop practical measures for BBTD control.
[_Banana bunchy top virus_ (BBTV) is the type member of the genus _Babuvirus_ (family Nanoviridae). It affects only _Musa_ species and hybrids. Most of today's cultivated bananas and plantains (banana types mostly eaten cooked) are polyploid hybrids related to either _Musa acuminata_ and/or _M. balbisiana_. BBTV causes one of the most serious diseases of these crops with symptoms of chlorosis, stunting, and death of the host plant. The virus is spreading in Africa, Australasia, and the Pacific Islands.
BBTV is transmitted by the banana aphid _Pentalonia nigronervosa_ in a persistent manner. Infectious insects may be spread on plant material or by air currents. The virus is also spread with infected suckers but cannot be transmitted by mechanical means (such as cutting tools). Disease management is extremely difficult and may include vector control, removal of inoculum, use of clean planting material, as well as frequent scouting for new outbreaks. Eradication of established BBTV from a planting or natural cluster of plants is considered impossible; the only option is to kill off all plants in the group. Tolerant varieties can be used to enable some crop production in infected areas, but these cultivars may still support virus replication and thus serve as pathogen reservoirs.
There are 2 groups of BBTV isolates from different regions: the South Pacific group (including Australia, Burundi, Egypt, Fiji, India, Tonga, Western Samoa) and the Asian group (including Philippines, Taiwan, Viet Nam). The mean sequence difference between the 2 groups has been reported as approximately 10% (see link below). This is thought to suggest that the virus has spread after the initial movement of its hosts from the Indo-Malayan region, where edible _Musa_ species originated, to Africa and the Americas.
BBTV is closely related to _Abaca bunchy top virus_ (ABTV) reported from some areas of SE Asia (ProMED post 20191215.6842101). ABTV and BBTV cause the same disease symptoms in both banana and abaca (_M. textilis_).
Bunchy top symptoms on banana:
Bunchy top photo galleries:
http://www.ctahr.hawaii.edu/banana/leaves_bunchy.asp (whole plants),
http://www.ctahr.hawaii.edu/banana/deformed_fruits.asp (fruits) and
http://www.ctahr.hawaii.edu/banana/closeup_photos.asp (banana aphids)
https://www.iita.org/news-item/international-multi-stakeholder-alliance-continue-to-tackle-banana-bunchy-top-disease-in-africa/ and via
https://www.bbtvalliance.org/ (BBTD Alliance)
Information on BBTV:
BBTV description and genetic groups:
ABTV description and characterisation:
Information on genus _Babuvirus_:
Virus taxonomy via:
Information on the banana aphid:
_Musa_ species and hybrids: