Thrips composition in North Indian cotton agroecosystem: a single species or a species complex?

Thrips have emerged as major sucking pests of American cotton Gossypium hirsutum L., limiting crop productivity through direct feeding and transmitting viral pathogens. Thrips have been long presumed to be a single species in cotton in northern India, with all the studies reporting it as onion thrips Thrips tabaci Lindeman (Thysanoptera: Thripidae). Even the majority of work from southern and central India reports it as the sole species in their studies conducted on pesticide efficacy, population dynamics, and host plant resistance etc. The present study entailed the sampling of cotton crop from 22 distinct locations representing the north-western, central, and southern zones of India using both morphological and molecular methods. The study reports the prevalence of a thrips species complex in cotton, which is dominated by melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), with the coexistence of other thrips species, viz., T. tabaci, Scirtothrips sp.,(Thysanoptera: Thripidae) and common blossom thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae). Our studies also throw light on the maiden reports of occurrence of orchid thrips, Chaetanaphothrips orchidii Moulton (Thysanoptera: Thripidae) and Asprothrips bimaculatus Michel & Ryckewaert (Thysanoptera: Dendrothripinae) thrips species in cotton from India. The genetic diversity analysis of T. palmi revealed the presence of cryptic species, and haplotyping showed the existence of 53 haplotypes globally, out of which two new haplotypes have been reported in the present study. The possible reasons for the change in cotton thrips composition from a single species to a complex over the years have also been analyzed using historical and conventional population dynamics data gathered over the past 15 years, which categorically indicated that the invasion of new species over the previous years might be responsible for the change in the population structure of thrips in cotton.

Graphical Abstract