A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Wed 6 Jun 2012
Source: Seed Today [edited]
Viral disease hits maize in Kenya's South Rift
Researchers and scientists have identified the strange disease which has destroyed thousands of acres of maize crops in South Rift as maize lethal necrosis.
Scientists from Kenya Agriculture Research Institute [KARI} said the disease is an infection made up of 2 viruses and is new in the country. Anne Wangai of KARI said the disease is a combination of maize chlorotic mottle virus and sugarcane mosaic virus. She said tests conducted on affected maize samples collected from the region positively identified the 2 viruses.
She said farmers from the affected regions should destroy their crops and plant alternative crops to curb further spread. The researcher also refuted claims that the disease is seed borne saying maize seeds [that] have been tested do not have any of the viruses. Dr Wangai said a diagnosis for the disease is yet to be established.
Agriculture minister Kosgey said the government has come up with a maize variety which is resistant to the disease [but] is still being verified by researchers. She urged farmers to implement agricultural practices that will step up the fight against the strange disease.
[So far, the presence of a number of fungal pathogens in the diseased maize in Kenya have been reported by various sources (ProMED-mail posts 20120117.1012452 and 20120326.1080612).
Now, 2 viruses have been added to the list of associated pathogens:
_Maize chlorotic mottle virus_ (MCMV, genus _Machlomovirus_), transmitted by chrysomelid beetle vectors, and _Sugarcane mosaic virus_ (SCMV, genus _Potyvirus_) transmitted by a number of aphid species. Neither of these viruses has been reported to be seed transmitted, but _Maize dwarf mosaic virus_ (MDMV, genus _Potyvirus_) which is closely related to SCMV and known to occur in the region can be transmitted in maize seed.
Since seed transmission (preferentially in hybrid H614) of the maize disease in Rift valley has been claimed earlier, it is possible that MDMV is the virus present but was misidentified as SCMV, especially since the disease mentioned above, maize lethal necrosis, is caused by co-infection of MCMV and either MDMV or _Wheat streak mosaic virus_.
In addition, other viruses are also present in the region, including _Maize streak virus_, and _Maize rough dwarf virus_, which was reported for the 1st time in Kenya from the Western Province in 2011 (ProMED-mail post 20110204.0407).
Despite the different pathogens reported from the diseased maize, it appears that more work is needed to clearly distinguish between primary causes of the problem and secondary or opportunistic pathogens.
<http://www.ogiek.org/photo-gallery/kenya-map-big.jpg> and <http://healthmap.org/r/2zip> Kenya provinces:
Maize lethal necrosis on field maize:
Single and combined infections of MCMV and MDMV in maize seedlings:
Photo galleries of maize diseases via:
Additional news stories:
Information on MCMV:
Information on SCMV:
Information on MDMV:
Virus taxonomy via:
Information on maize diseases via:
Undiagnosed disease, maize - Kenya (03): (RV) update 20120521.1139355 Undiagnosed disease, maize - Kenya (02): (RV) cephalosporium
Undiagnosed disease, maize - Kenya: (RV) 20120117.1012452
Maize dwarf mosaic virus - Uganda (KY): susp. 20111006.3002 Rough dwarf disease, maize - Kenya: 1st rep. 20110204.0407
Rough dwarf, maize - Africa: 1st rep (Uganda) 20100730.2552
Cephalosporium stripe, wheat - USA: (IL) 20080609.1829 Undiagnosed diseases, maize & bean - Angola: (BE), RFI 20080331.1186
Brown stalk rot, maize - South Africa: 1st report 20070620.1993
Maize streak mastrevirus - Kenya (West) (02) 20010417.0761 Maize streak mastrevirus - Kenya (West) 20010414.0743
Grey leaf spot, maize - Kenya (Rift Valley) 19991212.2151 and additional items on maize diseases in the archives]