Source: Plant Disease [summ. Mod.DHA, edited]
Citation: Mpoki S, Mahuku G, Mbanzibwa DR, et al. First report of banana bunchy top virus in banana and plantain (_Musa_ spp.) in Tanzania. Plant Dis. 105, First Look; https://doi.org/10.1094/PDIS-07-21-1387-PDN.
_Banana bunchy top virus_ (BBTV) was first reported in sub-Saharan Africa (SSA) in the 1960s in the Democratic Republic of Congo. Since then, BBTV spread was confirmed in 15 countries in the Central, Southern, and Western African regions but was not detected in any previous surveys in the East African sub-region.
Surveys in December 2020 - January 2021 in parts of Tanzania found banana plants with typical BBTV symptoms. Most of the affected plantations were 5-15 years old. Leaf samples from symptomatic and asymptomatic plants were tested with BBTV-specific polymerase chain reaction (PCR). All symptomatic plants were positive, and all asymptomatic plants were negative. To further confirm the virus identity, 4 samples each from symptomatic PCR-positive and asymptomatic PCR-negative plants were tested by triple antibody sandwich-enzyme-linked immunosorbent assay (TAS-ELISA). Samples from symptomatic plants were positive; samples from asymptomatic plants were negative.
For the 240 bp PCR products of 2 isolates, both strands were sequenced. A 99% nucleotide sequence identity with DNA-R sequences of several other BBTV isolates from Africa was found. Further phylogenetic analysis has grouped the 2 BBTV isolates with the sub-Saharan Africa sub-clade of the South Pacific group. To our knowledge, this is the 1st report of BBTV infecting bananas in Tanzania and East Africa.
[_Banana bunchy top virus_ (BBTV) is the type member of the genus _Babuvirus_ (family Nanoviridae) and affects only _Musa_ species and hybrids. Most of today's cultivated bananas and plantains (banana types mostly eaten cooked) are related to either _Musa acuminata_ (A) and/or _M. balbisiana_ (B), with the genetic background of polyploid hybrids indicated by the respective letters. 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-Malaysian 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)
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: