Gender-mediated differences in vertical transmission of a nucleopolyhedrovirus

With the development of sensitive molecular techniques for detection of low levels of asymptomatic pathogens, it becoming clear that vertical transmission is a common feature of some insect pathogenic viruses, and likely to be essential to virus survival when opportunities for horizontal transmission are unfavorable. Vertical transmission of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) is common in natural populations of S. exigua. To assess whether gender affected transgenerational virus transmission, four mating group treatments were performed using healthy and sublethally infected insects: i) healthy males (H=)6healthy females (HR); ii) infected males (I=)6healthy females (HR); iii) healthy males (H=)6infected females (IR) and iv) infected males (I=)6infected females (IR). Experimental adults and their offspring were analyzed by qPCR to determine the prevalence of infection. Both males and females were able to transmit the infection to the next generation, although female-mediated transmission resulted in a higher prevalence of infected offspring. Malemediated venereal transmission was half as efficient as maternally-mediated transmission. Egg surface decontamination studies indicated that the main route of transmission is likely transovarial rather than transovum. Both male and female offspring were infected by their parents in similar proportions. Incorporating vertically-transmitted genotypes into virusbased insecticides could provide moderate levels of transgenerational pest control, thereby extending the periods between bioinsecticide applications.

This work was supported by the Spanish Ministry for Science and Technology, project AGL2011-30352-C02-01. CV received a predoctoral fellowship from the Universidad Pública de Navarra.