Genetic identity of the Bemisia tabaci species complex and association with high cotton leaf curl disease (CLCuD) incidence in Pakistan

Abstract

The capacity to manage pests and disease effectively relies on knowledge of the identity of the agents causing the damage. In the case of CLCuD in Pakistan, this knowledge has been obscured to some extent because of the inconsistent approach to identifying and distinguishing the different B. tabaci associated with CLCuD. The situation has now been clarified, and a strong association between disease incidence and vector identity and abundance has been shown. Given this advance, future research can now focus on factors that influence the capacity of different vector species to transmit the viruses that cause CLCuD, the reason for differences in vector abundance and the lack of geographic overlap between the cryptic vector species. This knowledge will contribute to the development of improved methods with which to manage the disease in Pakistan.

DNA Barcoding of Bemisia tabaci Complex (Hemiptera: Aleyrodidae) Reveals Southerly Expansion of the Dominant Whitefly Species on Cotton in Pakistan

“…Sampling followed protocols outlined by Ahmed et al [11]. GPS coordinates were recorded [Table S1] and collection localities and species distributions were mapped using an online tool (www.simplemappr.net).…”

“…Members of the complex damage a wide range of agricultural and horticultural crops through both their feeding activity and their role in the transmission of plant viruses. Three members of the complex, Asia 1, Asia II 1, and Middle East-Asia Minor 1 (MEAM 1), have been previously identified from Pakistan where they are associated with the transmission of cotton leaf curl disease (CLCuD) which causes a significant reduction in yield [10], [11]. The severity of CLCuD varies across Pakistan with higher losses in central (Punjab) than southern (Sindh) Pakistan [12].…”

“…There has been a continuing debate as to the identity of the whitefly lineages in these regions and whether differences in the vector pool account for the differing levels of infection on cotton plants from these provinces. Ahmed et al [11] found that MEAM 1 was restricted to Sindh and Asia II 1 to the Punjab, whereas Asia 1 was found in both regions. Because Asia II 1 was associated with a higher incidence of CLCuD in both Punjab and northeastern India [11], [13], it is thought to play an important role in the transmission of this disease.…”

“…Ahmed et al [11] found that MEAM 1 was restricted to Sindh and Asia II 1 to the Punjab, whereas Asia 1 was found in both regions. Because Asia II 1 was associated with a higher incidence of CLCuD in both Punjab and northeastern India [11], [13], it is thought to play an important role in the transmission of this disease.…”

“…In this study, we use DNA barcodes to discriminate the lineages of B. tabaci found in India and Pakistan, reveal their genetic diversity and subsequently test if their distributions have shifted in the cotton-growing areas of Punjab and Sindh since a study in 2007–2009 [11]. We also employ barcodes to separate species of the B. tabaci complex and begin construction of the ‘translation’ matrix from COI-3′ to COI-5′.…”