Shoot and fruit borer, Leucinodes orbonalis (Guenee) (Pyraustidae: Lepidoptera), has become a production constraint in all eggplant (Solanum melongena Linn. [Solanaceae])-growing countries. In India, transgenic eggplants expressing Bacillus thuringiensis Cry toxins have been tested in fields by private- and public-sector agencies. Understanding population diversity is important in designing strategies for better pest management. In the present investigation, random-amplified polymorphic DNA markers were used to assess the genetic diversity of L. orbonalis population collected from different field locations in the Tamilnadu State of India. Of 17 random-amplified polymorphic DNA primers screened, only 11 primers generated polymorphic bands (up to 14 bands). According to their level of similarities, only two major clusters with no variation among population were deduced. Our results indicated that there is a steady genetic flow among the present population of L. orbonalis alleviating genetic variation, which may be attributed to passive and active dispersal of the insect besides absence of host-induced variations among the population. As molecular variability of L. orbonalis population is an important consideration for shoot and fruit damage of the eggplant, constant monitoring is essential to study the possible development of Cry protein resistance in L. orbonalis.

Problem statement: Whitefly, Bemisia tabaci is an important sucking pest of field, horticultural and ornamental plants causing feeding injuries besides spreading disease by acting as a vector of Gemini viruses. The polyphagous nature of the pest makes it as a highly complex species. Approach: The influence of host plants utilized by the species on the population differences at molecular level was attempted using Random Amplified Polymorphic DNA (RAPD) markers. Results: Ten RAPD primers out of the total seventeen primers screened produced 236 markers. The total number of bands obtained from each primer ranged from 11-35 with an average of 23.60 bands per primer. Of the pair wise combination among thirteen species, Srivilliputhur population showed the highest similarity index (0.826) while the lowest (0.111) was recorded by Namakkal population. The similarity coefficient based on the 236 RAPD markers generated ranged from 0.111-0.826. Three major clusters were formed from UPGMA dendrogram, which was constructed based on Jaccard's similarity. PCR screening demarcated the whitefly population based on the host species. The first cluster included population collected from okra and cotton, while second cluster comprised of population from eggplant and cauliflower and the third cluster included population from eggplant. It could be deduced that population from cotton and okra had 50% similarity, while 60-70% similarity was observed for population from eggplant and cauliflower. Conclusion: Our investigation offered the lead that within a narrow geographical region there exits variation based on host plants being utilized by the whitefly population.