STORED RICE WITHOUT LIPOXYGENASE-3 RESISTANCE TO A STORED GRAIN PEST IS DRIVEN BY A LACK OF INDUCED SUSCEPTIBILITY, NOT AN INDUCED DEFENSE

Résumé 0

"The angoumois grain moth, Sitotroga cerealella (Olivier), is one of the most serious pests attacking stored grain all over the world. Based on our earlier work, the relationship between lipoxygenase-3 (LOX-3) and the characteristic of resisting the angoumois grain moth were investigated in order to reduce the losses caused by the moth and to suppress its populations. LOX-3 near-isogenic lines of rice, Oryza sativa L., were obtained by backcrossing; they had similar genetic background while the enzyme activities of LOX-3 were different. Results from experiments of development and newly- hatched larvae orientation assay showed the S. cerealella development, reproductive success and newly-hatched larvae orientation not to be influenced by rice grain LOX-3 presence. Mated S. cerealella females responded positively to volatiles emitted from stored rice with LOX-3 in a choice test between stored rice with and without LOX-3; however, there was no significant difference when choosing between fresh rice with LOX-3 and without LOX-3. Results indicated that the loss of LOX-3 was related to the tropism of mated S. cerealella females and that the volatiles hexanal or pentanal emitted by stored rice grains might be attractants to S. cerealella females. The analysis found that a lack of induced susceptibility, rather than induced defense, explains the ‘resistance’ of stored rice without LOX-3 to S. cerealella."