Enhancing the virulence of AgMNPV

ROMANOWSKI, V; ARANA, E.; MCCARTHY, C.; BIEDMA, M.E; SCIOCCO-CAP, A; GOLDBERG, A; GHIRINGELLI, PD; PINEDO, F.; MOSCARDI, F.; RIBEIRO, B.

Curitiba

Workshop; Host-pathogen interactions AMSUD-Pasteur; 2003

Anticarsia gemmatalis is a key pest of soybean in Brazil, Argentina, and other countries. For a number of years a biopesticide based on the baculovirus AgMNPV has been used to control this pest in Brazil. However, a number of problems, including its low speed of kill, prevent the expansion of the use of the virus to the ca. 20 million hectares of soybean cultivated in South America. In order to address this problem we have recently developed a system for the genetic modification ofAgMNPV. The insertion of the insect-specific neurotoxin gene isolated from the mite Pyemotes tritici (TxP-1) yielded a rAgMNPV that paralyzed the host larvae within two days after treatment. On the other hand, the disruption of the egt gene eliminated the virally encoded enzyme that inactivates ecdysone, thus accelerating the moulting and the cessation of feeding. The egt(_) rAgMNPV killed the larvae 1-2.8 days faster than the wt virus (mean reduction of LT50 across virus concentrations: 2.2 days) and exhibited a higher virulence (LC50 3.9-fold lower than wt). Both rAgMNPVs significantly reduced the damage caused by the pest. Additionally, strategies of host range expansion in order to control simultaneous lepidopteran pests would certainly increase the appeal of AgMNPV to soybean growers. Controlled field experiments will address the applicability of these and other genetically improved AgMNPVs in large scale programs, that will include reporter genes to improve the traceabilty of the recombinants.