Isolation and RAPD-PCR Characterization of New Entomopathogenic Nematode Strains From Palestine

Isolation and RAPD-PCR Characterization of New Entomopathogenic Nematode Strains from Palestine Abstract Entomopathogenic nematodes (EPNs) are being applied as biocontrol agents against soil-borne pests. Since they exhibit host specificity, and because of the need for improving their infectivity and tolerance to environmental conditions it is necessary to enlarge the number of available species and strains. As the number of isolated species and strains increases, there will be a great need for convenient and reliable .methods of identification, genotyping and classification. Two EPN strains (Bethlehem I 1 and Bethlehem22) were isolated by trapping with larvae of Galleria mellonella from the fields of Bethlehem district, Palestine. The novel strains were identified as Heierorhabditis indica based on the successful crossings with another H. indica strain (LN2). There were 66% successful crosses between each of the Bethlehem strains and LN2 strain, while the percentage of successful crosses between Bethlehem strains was 83%. The Bethlehem strains were more heat tolerance when compared with H. hacieriophora from temperate climatic region. The survival of the 1.1s of the local strains was about 80%, while that of the H. bacteriophora strain approached Zero, when incubated at 40°C for 4 hours. The infectivity of the local strains was higher than that of the H. hacteriophora strain tested. The LD50 values after 26 hours exposure to G. VIII mellonella larvae were 25 for Bethlehem 11, 55 for Bethlehem22, and 160 IJs for H. bacteriophora. The novel strains are the first EPN strains that are isolated from Palestine. Studies on these strains are useful for the purpose to control local pests such as Maladera matrida. The two local strains were examined for their genetic relatedness to one another and to other EPN strains by Randomly Amplified Polymorphic DNA markers (RAPD). Results obtained by using seven primers showed that DNA banding patterns from Bethlehem strains are at 96.42% similarity, which indicate that they are different strains. Also, results showed that these strains are different from another H. indica strain, isolated from India, where an average similarity of 58.66% was observed. Moreover, the results revealed low similarity between the H. indica strains on one hand, and another strain belonging to the steinernema genus. This difference is expected since they belong to different genera. The RAPD-PCR technique cannot identify newly isolated strain at the species level. This is mainly because of the fact that this technique may show sometimes that the level of similarity between two species may be the same between two strains of the same species. On the other hand, this technique could be used to differentiate between two unknown strains.