Baseline susceptibility of Philippine Ostrinia furnacalis (Lepidoptera: Crambidae) populations to insecticidal Cry1A.105 and Cry2Ab2 proteins and validation of candidate diagnostic concentration for monitoring resistance

##plugins.themes.bootstrap3.article.main##

EDWIN P. ALCANTARA
MARNELLE M. ATIENZA
LUIS CAMACHO
SRINIVAS PARIMI

Abstract

Abstract. Alcantara EP, Atienza MM, Camacho L, Parimi S. 2021. Baseline susceptibility of Philippine Ostrinia furnacalis (Lepidoptera: Crambidae) populations to insecticidal Cry1A.105 and Cry2Ab2 proteins and validation of candidate diagnostic concentration for monitoring resistance. Biodiversitas 22: 956-960. This study estimated the baseline susceptibility of Ostrinia furnacalis populations from the Philippines, to purified insecticidal Cry1A.105 and Cry2Ab2 proteins and determined a diagnostic concentration (DC) through a validation experiment. The insect populations were collected from separate sites of corn farms in Northern and Central Luzon and in South Cotabato province of the island of Mindanao. Dose-response bioassays using artificial diet surface overlay method were conducted on eight populations. The bioassay results revealed that the LC50 of Cry1A.105 and Cry2Ab2 to O. furnacalis ranged from 0.03 ng/cm2 to 0.18 ng/cm2 and 1.40 ng/cm2 to 9.98 ng/cm2, respectively. The relative susceptibility ratios between the most susceptible and most tolerant populations were 6-fold for Cry1A.105 and about 7-fold for Cry2Ab2. The candidate diagnostic concentrations (DC) based on the LC99 were calculated using the baseline bioassay data for both Cry1A.105 and Cry2Ab2. The validation was performed on populations from the same locations used in the baseline susceptibility assay and a reference strain to produce at least 99% mortality for each protein. Data showed that populations tested with Cry1A.105 produced average mortality of at least 99% for the upper limit, while this was observed in the LC99 estimate for Cry2Ab2. The validated diagnostic concentration can be used for monitoring the resistance development of O. furnacalis exposed to Bt Corn, MON89034, in the Philippines.

##plugins.themes.bootstrap3.article.details##

References
Abbott WS. 1925. A method of computing the effectiveness of an insecticide. J. Econ. Entomol. 18, 265?267.
Alcantara EP, Estrada A, Alpuerto V, Head G. 2011. Monitoring Cry1Ab susceptibility in Asian corn borer (Lepidoptera: Crambidae) on Bt corn in the Philippines. Crop. Prot. 30:554-559.
Department of Agriculture (DA), Biotechnology Philippines. 2010. Determination of the Safety of Monsanto’s Corn MON 89034 for Direct use as Food, Feed, and for Processing and for Propagation. http://biotech.da.gov.ph/.
Han L, Liu P, Wu K, Peng Y, Wang F. 2008. Population Dynamics of Sesamia inferens on Transgenic Rice Expressing Cry1Ac and CpTI in Southern China. Environ. Entomol. 37(5), 1361?1370.
Jalali SK, Yadavalli L, Ojha R, Kumar P, et al. 2014. Baseline sensitivity of maize borers in India to the Bacillus thuringiensis insecticidal proteins Cry1A.105 and Cry2Ab2. Pest Mgt. Sci. 71 (8): 1082-1090.
Marcon CRGP, Young LJ, Steffey KL, Siegfried BD. 1999. Baseline susceptibility of European corn borer (Lepidoptera: Crambidae) to Bacillus thuringiensis toxins. J. Econ. Entomol 92:279–285.
Marcon CRGP, Siegfried BD, Spencer TA, Hutchinson, WD. 2000. Development of Diagnostic Concentrations for Monitoring Bacillus thuringiensis Resistance in European Corn Borer (Lepidoptera: Crambidae). Faculty Publications: Department of Entomology. 36.
Robertson JL, Priesler HK, Ng SS, Hickle LA, Gelernter WD. 1995. Natural variation: a complicating factor in bioassays with chemical and microbial pesticides. J. Econ. Entomol 88:1–10.
Sakuma, M. 1998. Probit analysis of preference data. Appl. Entom. Zool. 33, 339–347.
Sumerforf DV, Head GP, Shelton A, Greenplate J, Moar W. 2013. Field-evolved resistance: Assessing the problem and ways to move forward. J. Econ. Entomol. 106 (4):1525-1534.