Identification and Characterization of Maize Chlorotic Mottle Virus and Sugarcane Mosaic Virus Associated with Maize Lethal Necrosis Disease in Benishangul- Gumuz and Oromia Regions of Ethiopia
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Date
2016-10
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Addis Ababa University
Abstract
Maize (Zea mays L.) is a staple food for over 70 million peoples in Africa, and
predominantly produced and consumed directly by small scale holder families. Small scale holder farming operations in sub-Saharan encompasses over 25 million hectares. Ethiopia ranked second in Africa with annual maize production estimated to 3.98 metric tons per hectare. In 2013, Ethiopian farmers in some areas experienced high yield losses (30 to 100%) from a maize disease, later identified as Maize Lethal Necrosis Disease (MLND). The disease causes symptoms ranging from leaf tissue mottling and malformed ears to premature plant death. MLND develops from synergistic co-infection by Sugarcane Mosaic Virus and Maize Chlorotic Mottle Virus. Information on the diversity and transmission of those viruses are limited in Ethiopia. Hence, further information and understanding have valuable input on the control, diagnosis and management of MLND. No attempts were also made to characterize and identify
SCMV and MCMV strains of Oromia and Benishangul-Gumuz Regions of Ethiopia. Hence, this study was designed with the aim to study MLND responsible viruses via serological, molecular and artificial inoculation techniques. A total of 174 symptomatic leaf samples were collected from over 33 fields of
Oromia and Benishangul-Gumuz regions. The survey result reveals different degree of MLND incidence ranging from 10-100% infestation of study fields. Using DSMZ’s Double Antibody Sandwich-ELISA (DAS-ELISA) kit for serological assay, 43 samples showed strong reaction for MCMV antibody and only 14 samples were clearly positive for SCMV. Leaf samples from Benishangul-Gumuz didn’t react with the MCMV antibody used. Reverse transcriptase polymerase chain reaction (RT-PCR) technique using
specific viral primers revealed the presence of MCMC and SCMV in most samples. Some samples mainly from Benishangul-Gumuz region which were negative by DAS-ELISA were also positive by RTPCR suggesting that the method was more sensitive. Further confirmation of serological and RT-PCR based identification and analysis of the genetic diversity of epresentative viral strains was done by direct sequencing of the RT-PCR products. The results indicated that both SCMV and MCMV strains shows strong homology with previous East African isolates deposited in the GenBank. The phylogenetic tree indicated that the virus isolates are highly similar with each other. The haplotype networking showed there is less diversified MCMV, SCMV isolates are relatively highly diversified with almost all isolates Vas an individual haplotype, and MCMV isolates showed strong similarity to Chinese isolates with less number of mutations. The artificial inoculation results showed that virus strains from the study areas were able to cause mosaic and leaf streak or necrosis symptom on sweet corn planted in greenhouse. In conclusion, this study unequivocally confirmed the association of MCMV and SCMV with MLND in the study areas and for the first time provided information on the genetic variability by sequence analysis of several Ethiopian samples. Generally, symptoms, incidence, DAS-ELISA, RT-PCR and artificial inoculation results clearly showed the presence and diversity of MCMV and SCMV in the study area.
Key words: DAS-ELISA; genetic diversity; MLND; RT-PCR; Zea mays
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Keywords
DAS-ELISA; genetic diversity; MLND; RT-PCR; Zea mays