Advances towards improving the insecticidal properties of AgMNPV

VICTOR ROMANOWSKI; E. I. ARANA; CHRISTINA B. MCCARTHY; M.E. BIEDMA; A. SCIOCCO-CAP; A.V. GOLDBERG; P.D. GHIRINGHELLI; F.J. R. PINEDO; F. MOSCARDI; B. M. RIBEIRO

Burlington, Vermont

Congreso; 36th Annual Meeting of the Society for Invertebrate Pathology (SIP); 2003

Society for Invertebrate Pathology (SIP)

Anticarsia gemmatalis is a key pest of soybean in Brazil, Argentina, and other countries. AgMNPV is today the most widely used baculovirus pesticide, as more than two million hectares are treated annually. However, a number of problems prevent the expansion of the use of the virus to the ca. 20 million hectares of soybean cultivated in South America. A major drawback is the low speed of kill of wt AgMNPV, which becomes extremely important in areas with lower temperatures (20oC). In order to address this problem we have recently developed a system for the genetic modification of AgMNPV. To expand the number of alternative genetic modifications we introduced two unique sites for the intron-encoded IPpoI endonuclease to linearize the viral DNA used in cotransfections, which greatly reduced the background of non recombinant progeny. The insertion of the insect specific neurotoxin gene isolated from the mite Pyemotes tritici (TxP-1) yielded a rAgMNPV that paralysed the host larvae within two days after treatment. On the other hand, the disruption of the egt gene eliminated the viral 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. The traceabilty of the recombinants will be facilitated by the insertion of reporter genes.