F2 screen for resistance alleles in the Asian Corn Borer Ostrinia furnacalis guenee (Pyralidae: Lepidoptera)
2007
Cayabyab, B.F., Philippines Univ. Los Banos, College, Laguna (Philippines). National Crop Protection Center | Alcantara, E.P., Philippines Univ. Los Banos, College, Laguna (Philippines). National Inst. of Biotechnology and Molecular Biology | Sumaldo, A.C., Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Protection Cluster | Cuaterno, W.R., Bureau of Plant Industry, Malate, Manila (Philippines) | Siegfried, B.D., University of Nebraska, Lincoln, (NE) 830186 (USA). Dept. of Entomology | Malenab, M.C., Philippines Univ. Los Banos, College, Laguna (Philippines). Crop Protection Cluster
The refuge-high dose resistance management strategy has been recommended for Insect Resistance Management (IRM) of Bt corn in the Philippines. This is a preventive approach to resistance management without regard to the frequency of resistant insects in Asian Corn Borer (ACB) population. The F2 screening procedure can provide estimate of frequency of rare resistance alleles in natural insect populations and make them available for further testing. The procedure preserves genetic variation in isofemale lines and concentrate the resistance alleles in homozygous genotypes where it can be determined whether they are recessive or dominant. The protocol of Andow and Alstad (1998) on F2 screening was used in this study. Four hundred one females of the Asian corn borer collected from corn farms at Lubao, Pampanga from June to July 2006 were used to establish isofemale lines for the F2 screening to Cry 1 Ab protein. The progenies from each isofemale line were reared in the laboratory using artificial corn borer diet. Mating between siblings in each isofemale line was done to produce F2 neonate larvae. The neonate were screened for the presence of resistance alleles. Thirty two isofemale lines were produced and all of their larvae (1,601) were individually assayed using surface contamination technique with a discriminating dose of Cry 1 Ab (LCsub 99 = 120 ng/sq cm, Alcantara unpublished data) majority of the larvae produced from the F2 screen were found to be susceptible upon exposure to Cry 1Ab protein. It was also observed that the mortality rate for all of the 32 isofemale lines is at its peak during the first seven days of exposure to the toxin. Fourteen out of 32 isofemale lines or about 44% were potential positives since the larvae survived on the diet for more than seven days.
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