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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.

BACKGROUND The occurrence of Spodoptera frugiperda (J.E. Smith) in Asia was reported for the first time from Karnataka in 2018. This pest is widely distributed in India, causing significant damage to maize. Management of this recent invasive pest in maize‐growing regions of India relies on chemical control. Resistance is the greatest obstacle to the successful use of chemical insecticides to control this pest. Indiscriminate use of chemical insecticides destroys beneficial natural enemies, therefore effective and sustainable alternative control strategies are needed. In this case, the use of biological control agents is the alternative option to mitigate this pest. Thus, this study aimed to select virulent entomopathogenic nematodes (EPNs) isolates based on the laboratory assay and further to test the efficacy of virulent isolates in the field conditions along with commonly used chemical insecticide emamectin benzoate against S. frugiperda. RESULTS Laboratory results revealed that both Heterorhabditis indica 1 NBAIIH38 and Steinernema carpocapsae NBAIRS59 caused 100% mortality in third‐ and fourth‐instar larvae of S. frugiperda, while these two species caused 85% and 72% mortality in pupae, respectively. When pupae of S. frugiperda were exposed to EPNs, pupae died after metamorphosis to malformed adults. All the nematode species were able to penetrate and reproduce within S. frugiperda larvae, but the reproduction rate for Heterorhabditids was higher than that of Steinernematids. Field trial results showed that H. indica 1 NBAIIH38 significantly reduced the number of larvae and leaf damage scores compared to S. carpocapsae NBAIRS59. Emamectin benzoate was more effective in reducing the larval population compared to EPN species. The cob yield was significantly higher in EPN‐ and emamectin benzoate‐treated plots than in untreated control plots. CONCLUSION Overall, these experiments suggest H. indica 1 NBAIIH38 is a promising biocontrol agent against S. frugiperda in maize production. © 2022 Society of Chemical Industry.

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