Studies on Efficacy of Entomopathogenic Nematode Against Various Agricultural Pests in Vitro Condition

Abstract

Potato, the fourth most produced crop globally and the most important economic crop, is affected by various fungal, bacterial, and viral diseases. Brown rot of potato caused by Ralstonia solanacearum, common scab caused by Streptomyces scabies and soft rot caused by Pectobacterium carotovora sub sp. carotovora are the most significant bacterial diseases. A study was conducted on potato fields in six blocks of the Meerut District from January to March 2024. In this study it was found that the none of the tuber samples affected with brown rot and soft rot while the highest incidence of common scab was observed in Daurala block (3%) followed by Janikhurd (2.6%), Sardhana (2.5%), and Meerut Sadar (2.2%). The least disease incidence was recorded in Mawana (1%) and Kharkhauda (2%). Six Streptomyces isolates were isolated from 80 infected tubers in which four isolates exhibited the same cultural characteristics as Streptomyces scabies, such as extensive aerial growth of mycelia and creamy white or grey colony color. Further verification of these isolates were performed using cultural characteristics on various mediums. Brown colonies were seen on Starch Casein Agar, Potato dextrose agar, and Yeast extract-malt extract agar from all four isolates. White colony were seen on the Nutrient agar medium. PCR amplification of the 16srDNA gene led to a 1500 bp segment amplification in two isolates. In-vitro drug sensitivity assay by disc diffusion method indicated that all isolates showed no zone of inhibition to drugs Aztreonam and least inhibition to drugs Imipenem. Amikacin showed the maximum inhibition zone (26mm), followed by Carbenicillin (15mm) and Piperacillin (9.5mm). Four different bioagents were evaluated against Streptomyces scabiei using disc diffusion method, in which T. harzianum showed the highest zone of inhibition (35mm) followed by T. viride (29.5mm) and Bacillus subtilis (23mm). Pseudomonas fluorescens found to be least effective against Streptomyces scabies (10.5mm).