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Genetic Structure of Field Populations of Begomoviruses and of Their Vector Bemisia tabaci in Pakistan

First and second authors: Centro de Investigación y Desarrollo Agroalimentario, 30150 La Alberca (Murcia), Spain; third author: Departamento de Protección Vegetal, CIT-INIA, Carretera de La Coruña Km.7,5, 28040 Madrid, Spain; fourth author: Institute of Crop and Environmental Protection, Crop Diseases Research Programme, National Agricultural Research Centre, Islamabad 45500, Pakistan; and fifth, sixth, and seventh authors: Departamento de Biotecnología, ETS Ingenieros Agrónomos, 28040-Madrid, Spain

The genetic structure of field populations of begomoviruses and their whitefly vector Bemisia tabaci in Pakistan was analyzed. Begomoviruses and B. tabaci populations were sampled from different crops and weeds in different locations in Punjab and Sindh provinces, in areas where cotton leaf curl disease (CLCuD) occurs or does not occur. Phylogenetic analysis based on nucleotide sequences of the intergenic region in the viral DNA-A provided evidence of two clusters of isolates: viruses isolated from species in the family Malvaceae, and viruses isolated from other dicotyledon families. Analysis of the capsid protein (CP) open reading frame grouped isolates into three geographical clusters, corresponding to isolates collected in Punjab, Sindh, or both provinces. Random amplified polymorphic DNA analyses of the B. tabaci population showed that intrapopulation diversity was high at both the local and regional scales. Sequence analysis of the mitocondrial cytochrome oxydase I (mt COI) gene showed that the B. tabaci population was structured into at least three genetic lineages corresponding to the previously described Indian, Southeast Asian, and Mediterranean-African clades. The Indian clade was present only in Punjab, the Mediterranean-African only in Sindh, and the Southeast Asian in both provinces. B. tabaci haplotypes of the Indian clade were found only in the Punjab, where CLCuD occurs. Hence, the geographical distribution of virus and vector genotypes may be correlated, because similar phylogenetic relationships were detected for the viral CP and the vector mt COI genes.