Abstract
The polyphagous mirid bug Apolygus lucorum (Heteroptera: Miridae) has more than 200 species of host plants and is an insect pest of important agricultural crops, including cotton (Gossypium hirsutum) and mungbean (Vigna radiata). Previous field trials have shown that A. lucorum adults prefer mungbean to cotton plants, indicating the considerable potential of mungbean as a trap crop in cotton fields. However, direct evidence supporting the migration of A. lucorum adults from cotton to mungbean is lacking. We developed a DNA-based polymerase chain reaction (PCR) approach to reveal the movement of A. lucorum between neighboring mungbean and cotton fields. Two pairs of PCR primers specific to cotton or mungbean were designed to target the trnL-trnF region of chloroplast DNA. Significant differences in the detectability half-life (DS50) were observed between these two host plants, and the mean for cotton (8.26 h) was approximately two times longer than that of mungbean (4.38 h), requiring weighted mean calculations to compare the detectability of plant DNA in the guts of field-collected bugs. In field trials, cotton DNA was detected in the guts of the adult A. lucorum individuals collected in mungbean plots, and the cotton DNA detection rate decreased successively from 5 to 15 m away from the mungbean-cotton midline. In addition to the specific detection of cotton- and mungbean-fed bugs, both cotton and mungbean DNA were simultaneously detected within the guts of single individuals caught from mungbean fields. This study successfully established a tool for molecular gut-content analyses and clearly demonstrated the movement of A. lucorum adults from cotton to neighboring mungbean fields, providing new insights into understanding the feeding characteristics and landscape-level ecology of A. lucorum under natural conditions.
Highlights
Transgenic Bacillus thuringiensis (Bt) cotton was widely adopted for management of Helicoverpa species infestation in northern China during the late 1990s
The results showed that all extracted plant DNA samples, except for the negative controls, exhibited a similar 120 bp band when general plant primers targeting the tRNA for leucine (trnL) region were used (S1 Fig), indicating the successful plant DNA extraction
The results of a cross-reactivity test revealed that the primers designed for cotton and mungbean amplified bands of 236 bp and 199 bp, respectively, and sequencing verification confirmed that these products were cotton and mungbean
Summary
Transgenic Bacillus thuringiensis (Bt) cotton was widely adopted for management of Helicoverpa species infestation in northern China during the late 1990s. As a polyphagous herbivorous pest, A. lucorum has more than 200 recorded host plant species and causes economic injury to cotton and other crops, including fruit trees and tea plants [3,4,5]. Such a broad host range together with its remarkable reproduction ability, longdistance dispersal capacity [6] and relatively inefficient control by predators [7] increases the destruction by these pests. The suppression of mirid bug populations in the field still relies heavily on chemical pesticide applications, leading to problems associated with resistance development, pest resurgence and environmental pollution; an environmentally friendly pest management strategy is required, such as “push-pull” habitat management that utilizes repellent plants and attractant trapping crops to manipulate the population density of pests on the target crop [8]
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