Rapid spread of a densovirus in a major crop pest following wide-scale adoption of Bt-cotton in China

Abstract

Bacillus thuringiensis (Bt) crops have been widely planted and the effects of Bt-crops on populations of the target and non-target insect pests have been well studied. However, the effects of Bt-crops exposure on microorganisms that interact with crop pests have not previously been quantified. Here, we use laboratory and field data to show that infection of Helicoverpa armigera with a densovirus (HaDV2) is associated with its enhanced growth and tolerance to Bt-cotton. Moreover, field monitoring showed a much higher incidence of cotton bollworm infection with HaDV2 in regions cultivated with Bt-cotton than in regions without it, with the rate of densovirus infection increasing with increasing use of Bt-cotton. RNA-seq suggested tolerance to both baculovirus and Cry1Ac were enhanced via the immune-related pathways. These findings suggest that exposure to Bt-crops has selected for beneficial interactions between the target pest and a mutualistic microorganism that enhances its performance on Bt-crops under field conditions.

Symbiotic Interactions Between Mosquitoes and Mosquito Viruses

“…For example, parasitoid wasps harbor a beneficial vertically transmitted entomopoxvirus that ensures the development of the wasp larvae within the wasp’s insect host ( Coffman et al., 2020 ). Insect viruses with beneficial traits have also been shown in lepidopteran species where a vertically transmitted Helicoverpa armigera densovirus increases developmental rates, lifespan, female fecundity, and more importantly resistance against pathogenic Bacillus thuringiensis and a baculovirus in laboratory conditions ( Xu et al., 2014 ; Xiao et al., 2021 ). Hence, this densovirus can be beneficial to its host, specifically in the areas where B. thuringiensis or baculovirus based population control tools are commonly deployed ( Xiao et al., 2021 ).…”

“…Insect viruses with beneficial traits have also been shown in lepidopteran species where a vertically transmitted Helicoverpa armigera densovirus increases developmental rates, lifespan, female fecundity, and more importantly resistance against pathogenic Bacillus thuringiensis and a baculovirus in laboratory conditions ( Xu et al., 2014 ; Xiao et al., 2021 ). Hence, this densovirus can be beneficial to its host, specifically in the areas where B. thuringiensis or baculovirus based population control tools are commonly deployed ( Xiao et al., 2021 ). Another conditional beneficial interaction has been reported between the rosy apple aphid and Dysaphis plantaginea densovirus (DplDV) ( Ryabov et al., 2009 ) which causes the appearance of wings in a proportion of genetically identical clonal aphids in poor diet conditions ( Ryabov et al., 2009 ).…”

Adaptive evolution to the natural and anthropogenic environment in a global invasive crop pest, the cotton bollworm

“…However, Bt resistance has been reported, especially in Asia and Australasia. 15 , 16 H. armigera has remarkable dispersal ability, and adults are capable of high-altitude, long-range flight. 11 Therefore, despite its extensive geographic range, little population structure has been observed using genetic markers, apart from the Australasian subspecies H. armigera conferta .…”

Identification of a Novel Densovirus in Aphid, and Uncovering the Possible Antiviral Process During Its Infection

“…Hence, DVs are protein agents in the pathogen vectors and pest control ( 45 – 47 ). Recently, mutualistic DV has also been reported in Helicoverpa armigera ( 48 ), and rapid spread in the wild moth populations ( 49 ). In aphids, MpDV1 negatively affects the fitness of M. persicae ( 21 ), DplDV1 induces winged morphs in D. plantaginea ( 22 ).…”