Realized Heritability, Risk Assessment, and Inheritance Pattern in Earias vittella (Lepidoptera: Noctuidae) Resistant to Dipel (Bacillus thuringiensis Kurstaki)

Abstract

Earias vittella Fabricius is a potential cotton and okra pest in South Asia. The realized heritability, risk assessment, and inheritance mode of Bacillus thuringiensis Kurstaki (Btk) resistance were determined in the Dipel-selected (DIPEL-SEL) E. vittella. The DIPEL-SEL strain had a 127.56-fold rise in Dipel resistance after nine generations compared to the laboratory reference strain (LAB-PK). The overlapping of 95% fiducial limits in the median lethal concentrations (LC50s) of the F1 (DIPEL-SEL♂ × LAB-PK♀) and F1ǂ (DIPEL-SEL♀ × LAB-PK♂) suggested a lack of sex linkage and an autosomal Dipel resistance. The dominance (DLC) values for the F1 (0.86) and F1ǂ (0.94) indicated incompletely dominant resistance to Dipel. Backcrossing of the F1♀ × Lab-PK♂ revealed a polygenic response of resistance to Dipel. The realized heritability estimation (h2) of resistance to Dipel was 0.19. With 20% to 90% selection mortality, the generations required for a tenfold increase in LC50 of Dipel were 4.7–22.8, 3.1–14.9, and 2.3–11.1 at h2 of 0.19, 0.29, and 0.39, respectively, and a constant slope of 1.56. At slope values of 2.56 and 3.56 with a constant h2 = 0.19, 7.7–37.4 and 10.6–52.0 generations were needed to increase the tenfold LC50 of Dipel in the DIPEL-SEL E. vittella. It is concluded that the DIPEL-SEL E. vittella has an autosomal, incompletely dominant, and polygenic nature of resistance. The h2 of 0.19 suggested that a high proportion of phenotypic variation for the Dipel resistance in E. vittella was heritable genetic variation. The present results will support the creation of an effective and suitable resistance management plan for better control of E. vittella.