Genetic Variation in the Invaded Population of the Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), in India

The fall armyworm, Spodoptera frugiperda, an invasive, polyphagous pest, causes significant damage to corn. The majority of insects rely on a broad range of digestive enzymes and an intricate detoxifying mechanism to consume chemically diverse host plants. The genetic variation in S. frugiperda was analyzed using cytochrome oxidase subunit I (COI) and triose phosphate isomerase (Tpi). In addition, a new attempt was made to determine the variation with respect to two detoxifying genes, viz., carboxylesterase and glutathione S-transferase. The highest genetic variation (3.03%) was found between the S. frugiperda populations of Tirupati and Delhi with respect to the Tpi gene and between the populations of Punjab and Hosur regarding COI (3.30%). The results for various genes revealed that populations of the fall armyworm were homogeneous, showing low genetic distance using COI, ranging from 0.40 to 3.30%, and, using Tpi, ranging from 0.43 to 3.03%. The variation in carboxylesterase and glutathione S-transferase ranged from 0.04 to 0.15% and from 0.01 to 0.02, respectively. Amino acid sequences were also produced using DNA sequences from several fall armyworm populations. Populations in Tirupati, Solapur, and Hyderabad shared 98.7% of their sequence with that in Delhi. Fall armyworm amino acid sequences showed 79.7 to 82.0% identity with S. exigua and 69.6 to 73.0% identity with S. litura. Our study provides vital information for understanding the genetic variation in the fall armyworm following its invasion of India.