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

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.

Seven Years of Monitoring Susceptibility to Cry1Ab and Cry1F in Asian Corn Borer

“…As ACB is one of the most destructive insect pests of corn throughout Asia and Southeast Asia, the baseline susceptibility of different geographic populations of ACB to Cry1Ab or Cry1A.105 has been estimated in several countries, including China, Vietnam, and the Philippines [ 19 , 20 , 25 , 26 ]. In 2005, the baseline susceptibility to Cry1Ab of ACB from the corn belt across the northeast and east-central parts of China was first reported [ 25 ].…”

“…In the Philippines, MON89034, a pyramided transgenic corn event expressing Cry1A.105 and Cry2Ab2 that were highly effective against ACB, was approved for commercial use in 2010. The interpopulation variation in susceptibility to Cry1A.105 and Cry2Ab2 among populations have been reported to be <10-fold [ 19 ].…”

“…Asian corn borer (ACB), O. furnacalis (Guenée) (Lepidoptera: Crambidae), is one of the most destructive pests of corn in China, Japan, and countries of Southeast Asia, including Vietnam and the Philippines, as well as Australasia and the Pacific [ 17 ]. It can cause considerable yield losses that have been previously reported to be in the range of 10% to 80% and pose a major threat to food security [ 18 , 19 ]. In the Philippines, single trait event MON810 (expressing Cry1Ab protein) commercialization started in 2003, following the strict regulations set by the Department of Agriculture for biotech cultivation approved and signed in 2002 [ 19 ].…”

“…It can cause considerable yield losses that have been previously reported to be in the range of 10% to 80% and pose a major threat to food security [ 18 , 19 ]. In the Philippines, single trait event MON810 (expressing Cry1Ab protein) commercialization started in 2003, following the strict regulations set by the Department of Agriculture for biotech cultivation approved and signed in 2002 [ 19 ]. In 2015, the Ministry of Natural Resources and Environment approved Syngenta’s Bt11 (expressing Cry1Ab protein) corn for commercial cultivation in Vietnam [ 20 ].…”

Baseline Susceptibility of the Field Populations of Ostrinia furnacalis in Indonesia to the Proteins Cry1A.105 and Cry2Ab2 of Bacillus thuringiensis

“…Several Bt corn technologies are currently in the process of registration in Indonesia [17], including the MON 89034 corn. MON 89034 is a pyramided transgenic corn event expressing two Bt proteins, Cry1A.105 and Cry2Ab2, that are highly effective against key lepidopteran corn pests [18][19][20]. MON 89034 has been approved for commercialization in the Philippines since 2010 and in Vietnam since 2015 as a viable alternative for the sustainable control of O. furnacalis and other corn lepidopteran pests [15,21,22].…”