MAIZE RESPONSE TO FALL ARMYWORM (SPODOPTERA FRUGIPERDA) AND ASIAN CORN BORER (OSTRINIA FURNACALIS) IN THE PHILIPPINES

Abstract

Philippine traditional maize has long existed for hundreds of years, facing and coping with continuous threats of different pests and diseases, with Asian corn borer and fall armyworm as the most damaging insect pests. Developing resistant varieties can employ rich genetic resources, as these varieties may have likely adapted to these biotic stresses. The development of ACB-resistant varieties proved successful with the Bt corn introduction; however, the attempt to breed for resistance to FAW is still underway. The two insect pests belong under the same Order, and cross-resistance between these pests may be possible. In this study, several traditional maize varieties underwent screening for resistance to ACB and FAW through larval survival on leaf-feeding assay. Among the accessions observed, three variants of APN 0120 (Silangan) and three other traditional maize (APN 0397, APN 0913, APN 0938) showed intermediate to high resistance toward FAW leaf damage. Few of these resistant varieties showed negative to Bt introgression. The most notable is the variant SI of APN 0120, with high resistance to ACB and FAW and low larval weight, without the presence of Bt. A previous report stated the original collection of this accession have potential ACB resistance, although Bt-introgressed. On the other hand, APN 0397 (Lagkitan), introgressed with Bt Cry1Ab, expressed dual resistance to ACB and FAW, too. It elucidates the reaction and potential of previously screened ACB-resistant varieties against FAW and the efficiency of Cry1Ab against FAW. It also demonstrates the potential of the traditional maize as source of germplasm to be explored to promote the utilization of open-pollinated varieties with inherent insect resistance. Moreover, this paper establishes massrearing procedures and laboratory techniques for effective fall armyworm-resistance screening using excised leaf method.