Distribution of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Mitotypes in Commercial Cotton Fields in the Punjab Province of Pakistan

Abstract

The Bemisia tabaci (Gennadius) (Hemiptera: Aleyroridae) sibling species group is comprised of genetic variants defined by biological differences or a fragment of mitochondrial cytochrome oxidase I gene sequence (mitotype) that allows for phylogeographic affiliation. Some mitotypes may cause damage to crop plants by feeding and transmission of plant viruses. In Pakistan, cotton-vegetable agroecosystems are vulnerable to whitefly-transmitted virus (genus Begomovirus; family Geminiviridae) infection. The identity and distribution of the whitefly B. tabaci mitotypes associated with the cotton crop were studied in 8 districts in the Punjab Province from 2014 to 2016. Phylogenetic analysis of the 3ʹ-fragment of the mitochondrial cytochrome oxidase I gene indicated the predominant haplotypes belonged to the Asia II-1 mitotype, with pairwise distances ranging from 0.15 to 3.2%. Pairwise distances showed that B. tabaci haplotype diversity varied by district, with the Khanewal harboring the highest divergence at 1.37%, compared to the lowest at 0.50% in the Dera Ghazi Khan district. The median-joining network analysis showed genetic expansion, or a ‘recovery’ trend, following the declining genetic diversity that occurred during the late 1990s to the early 2000s. The Asia II-1 mitotype group was the predominant whitefly vector species in Punjab Province. The haplotype network provides documentation of continued genetic expansion among the B. tabaci populations in the Punjab, which is consistent with previously reported trends among whiteflies sampled in the same or nearby districts from 2012 to 2014. Genetic expansion varied among districts and could be explained by factors unique to each district, i.e., management practices that influence B. tabaci mitotype composition, whitefly susceptibility to cotton leaf curl disease complex, and cotton genotype Key Words: haplotype; median-joining network analysis; mitochondria cytochrome oxidase I gene; phylogenetic analysis; population genetics Resumen El complejo de moscas blancas Bemisia tabaci (Gennadius) (Hemiptera: Aleyroridae), comprende grupos geneticos cuya afiliacion filo-geografica puede ser determinada mediante una serie de rasgos biologicos o el uso de un fragmento del gen mitocondrial citocromo oxidasa I (mitotipo). Algunos mitotipos de B. tabaci pueden ocasionar danos economicos importantes en cultivos comerciales debido a su alimentacion y a la transmision efectiva de virus vegetales, por ejemplo, en Paquistan, los agro-ecosistemas de algodon son altamente vulnerables a virus transmitidos por moscas blancas (genero Begomovirus; familia Geminiviridae). En este articulo, se estudio la identidad y distribucion geografica de los principales mitotipos de B. tabaci que se encuentran infestando parcelas comerciales de algodon en 8 distritos de la provincia de Punjab, Paquistan, durante los anos 2014-2016. Se determino mediante un analisis filo-genetico del fragmento 3 ʹ del gen citocromo oxidasa I, que el haplotipo mas predominante pertenecio al mitotipo Asia II-1, con distancias geneticas que variaron entre 0.15-3.2%. Se determino que las distancias geneticas entre haplotipos varian por distrito geografico, con la divergencia mas alta de 1.37% en Khanewal, comparado con la divergencia mas baja de 0.50% en el distrito Dera Ghazi Khan. Se demostro mediante un analisis de red de haplotipos, que la poblacion de moscas blancas continua en un proceso de expansion genetica que varia por distrito, lo que coincide con un escenario de expansion demografica reportada en poblaciones de mosca blanca colectadas en localidades similares durante el periodo 2012-2014. El patron geografico de expansion observado puede ser atribuido a factores unicos de cada distrito geografico, por ejemplo: practicas de manejo de plagas que alteren la composicion mitotipica de la mosca blanca, eficiencia del vector para transmitir virus y genotipo de algodon sembrado. Palabras Claves: haplotipo; red de haplotipos median-joining; gen mitocondrial citocromo oxidasa I; analisis filogenetico; genetica de poblaciones View this article in BioOne