During the survey in the banana field, one positive EPN isolate was recovered from 15 soil samples collected from different locations throughout the field. The isolate of Heterorhabditis was identified and characterized, using a combination of morphological and molecular techniques. Molecular identifications based on sequences of the ITS region were supported by morphological observations. According to the results obtained, the isolate was H. indica.
The occurrence of EPNs in the study area was relatively high (7%). The recovery rate for EPNs at this region was expected to be high due to several factors, as the nature of the soil sample is sandy clay loam and the temperature ranging from 23 to 25°C. This agrees with the findings of Valadas et al. (2013) and Khashaba et al. (2020); also, the sample size increase the probability of positive samples.
The phylogenetic tree based on ITS sequence showed that H. indica Aborawash and ERSAG2 belong to the same clade with other H. indica species, while the isolate ERSAG in the other clade; this might be due to the geographical difference as Dolgin et al. (2008) called “latitudinal clades.”
The genetic characteristics of a species are affected primarily by various ecological and biological traits, modes of reproduction, and breeding. For reconstructing the phylogeny of the EPNs, many molecular techniques have been used, for instance, random amplified polymorphic DNA (RAPD), restriction fragment length polymorphisms (RFLP), and more recently DNA sequencing, and mitochondrial genes (ND4), simple sequence repeats (SSR), and sequence-related amplified polymorphism (SRAP) have been the most extensively applied (Padmanaban et al. 2014; Abd Elazim et al. 2019).
The SCoT marker systems are proved to be an efficient and inexpensive way to provide molecular data to assess genetic diversity, and it has been used successfully to determine genetic relationships for many plants as reported by Bhattacharyya et al. (2013), but there are no studies being applied about the application of SCoT marker to assess the genetic diversity among entomopathogenic nematode species.
Abu Almaaty (2020) evaluated the genetic variability among 3 gastropod species, using 10 SCoT primers, produced 115 amplicons; their size ranged from 120 to 1500 bp and revealed that the percentage of polymorphism ranged from 20 to 78%. Reporting from all the gained data, it is evident that molecular detection of SCoT is a suitable tool in assessing genetic variations and relationships among gastropod species. Bhawna et al. (2017) used 20 SCoT markers for studying the genetic diversity analysis, gene flow, and population structure in the 39 bottle gourd germplasm collected from different regions of India, and the polymorphism percentage was 82.61. From the obtained results, it could be concluded that SCoT markers are promising markers in research for diversity analysis and to target genes easily for the breeder, geneticist, and evolutionists. Also, Satya et al. (2015) used 24 (SCoT) markers to assess the genetic diversity and population structure of indigenous, introduced, and domesticated ramie (Boehmeria nivea L. Gaudich.), producing 136 amplicons with 87.5% polymorphism and concluded that the SCoT technique would be useful for further studies in population genetics, conservation genetics, and cultivar improvement.
Therefore, the SCoT marker used in this study was found to be useful and effective for estimating the genetic relationships among indigenous EPNs belonging to H. indica species and could be assessed on a wide range of applications in EPNs for evaluating the genetic polymorphism.