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Potato cyst nematode (PCN) is considered to be the most devastating pest causing major yield losses in potato worldwide. Resistant potato cultivars would be the most effective strategy to control PCN however, they may not posses enough resistance to all pathotypes of PCN. Therefore breeding programme should focus on developing varieties with horizontal resistance which can be achieved by using parental lines with multiple resistant genes. Hence, the present study was conducted to characterize the phenotypic and genotypic resistance of parental lines against PCN and also an attempt was made to find out the pollen viability of the parental lines to improve the breeding efficiency. Sixty six genotypes were screened phenotypically as well as genotypically against PCN. Out of which, 54 lines were found phenotypically resistant to G. rostochiensis, 48 to G. pallida and 44 to both the species of PCN. The same set of parental lines was also validated using linked molecular markers. In molecular characterization, the markers linked with H1 gene (TG689 and 57R) were found in majority of the parental lines screened. Marker SPUD 1636 linked to GPa5 QTL was positive for three genotypes whereas HC marker (GPaVvrn QTL) was positive for 30 parental lines. TG432 linked to Grp1 gene is positive for 27 parental lines whereas the marker Gro 1-4-1 is not amplified in any of the screened parental lines. Pollen viability of parental lines varied from 15.8 to 93.6%. The results of the study will facilitate breeding of novel resistant varieties by efficient selection of ideal male parent with good pollen potential and multiple resistance to several PCN pathotypes.

Potato (Solanum tuberosum L.) is the third important food crop in the world (Raymundo et al., 2017) and has the potential to mitigate the challenge of nutritional security. It is a rich source of carbohydrates, dietary fibres, minerals, phytonutrients, proteins, vitamins, etc. and therefore called as 'nutritional depository' (Mishra et al., 2020). In India, potato is being grown in 2.15 million ha with a production of 48.53 million tonnes that accounts for approximately 12% of total world production (FAOSTAT, 2018).

The potato tuber moth, Phthorimaea operculella (Zeller), is a serious pest of potato and other commercial crops belonging to the Solanaceae family. In recent years, it has become an emerging problem in potato-growing regions of the Nilgiri hills of southern India. It is responsible for the reduced quality and quantity of marketable potatoes. In this regard, the development of an eco-friendly control method for the management of the potato tuber moth is urgently required. Therefore, in the present study, the virulence of Steinernema cholashanense CPRSUS01 originally isolated from the potato rhizosphere was tested on fourth-instar larvae and pupae of P. operculella. Steinernema cholashanense caused the greatest mortality in the fourth-instar larval stage (100%) than the pupae (30%). In addition to this, penetration and reproduction of this nematode was also studied in fourth-instar larvae of P. operculella and this is the first report of penetration and reproduction of any entomopathogenic nematode species on potato tuber moth larvae. The reproduction capacity of S. cholashanense on P. operculella is higher (702 infective juveniles mg−1 body weight). Our results indicated that S. cholashanense has good potential as an alternative tool for the management of P. operculella. But before including S. cholashanense in the integrated pest management program of P. operculella, its efficacy should be tested under field conditions.