Begomoviruses associated with weeds and legume crops in Mozambique: emergence, variability and recombination-driven evolution

• Ano de defesa: 2021
• Autor(a) principal: Chipiringo, Baltazar do Azarento Isabel
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Begomovirus; Recombinação (Genética); Leguminosa - Doenças e pragas; Fitopatologia
• Link de acesso: https://locus.ufv.br//handle/123456789/28191

Agriculture in Mozambique is moving towards "modernization", with increased areas of monoculture, extended growing seasons, irrigation and mechanization replacing subsistence farming. However, such changes in agricultural practices can promote pathogen emergence. Understanding the emergence and evolution of plant viruses provides beneficial information on management practices. This work aimed at the detection, identification and molecular characterisation of begomoviruses associated with legumes and weeds in Mozambique. In the first study, a non-cultivated plant identified as Pyrenecantha sp. (Icacinaceae) with yellow mosaic symptoms was collected in the district of Malema, Nampula province. The viral genome was amplified using rolling-circle amplification, cloned and sequenced. The DNA-A has the highest identity (78%) with tomato leaf curl Namakele virus, while the DNA-B sequence has the highest identity (70%) with Deinbolia mosaic virus. The two components have a genomic organization typical of Old World, bipartite begomoviruses. Alignment of their common regions (CR) indicated a 35-nt insertion in the DNA-A CR. The identity between the CRs is 83%, increasing to 96% when the 35-nt insertion is removed from the alignment. The CRs have identical iterons, and the amino acid sequence of the Rep protein contains the iteron-related domain predicted to recognize these iterons. These results indicate that the cloned DNA-A and DNA-B are cognate components of the same virus, and the 35-nt insertion suggests a recombination event in the DNA-A CR. The name Pyrenecantha yellow mosaic virus is proposed for the new virus. For the second study, symptomatic samples of bean, cowpea and soybean plants were collected in the central and northern regions of Mozambique. Seven DNA- A and 11 DNA-B components were cloned and sequenced. The DNA-A sequences are 96% identical, indicating that they represent the same virus. The highest identity with other begomoviruses is 85% with cowpea golden mosaic virus. The DNA-B sequences are 93% identical amongst each other and have a maximum of 72% identity with cotton yellow mosaic virus. Alignment of the CRs indicates that the DNA-A and DNA-B components are cognate components of the same virus. The name Mozambique legume mosaic virus is proposed. Three recombination events were detected in the DNA-B. The DNA-B is more variable than the DNA- A, and the DNA-B nucleotide diversity is higher in the MP gene and in the short intergenic region. MLMV is an emerging begomovirus in legume crops in Mozambique, and its adaptation to new hosts appears to be driven by recombination in the DNA-B. Keywords: Pyrenacanthae. PyYMV. 35-nt. MLMV. Mozlegume. Bean. Soybean. Cowpea.