Comparative in vitro efficacy of biological agents, plant extracts and novel fungicides for controlling seed-borne pathogens in cucumber (Cucumis sativus L.)

Cucumber (Cucumis sativus) belongs to the family Cucurbitaceae. Cucumbers are an important part of human diets as they contain essential vitamins, minerals and antioxidants. They are among the most significant commercial crops and are vital to the overall livelihood and food security of the people. They are well known for alleviating constipation, lowering blood sugar levels and treating jaundice, among health benefits. Cucumbers, however, are highly susceptible to attacks from various seed-borne pathogens. Seed-borne fungi such as Aspergillus niger (ITCC I.D. No. 11966.23) and A. flavus were identified from cucumber seeds through pathogenicity tests and cultural as well as morphological characterization. Among the ten fungicides tested, chlorothalonil exhibited the highest inhibition (100 %) A. niger, while Propiconazole was the most effective against A. flavus (100 %). Three bioagents were also evaluated, with Trichoderma harzianum showing the highest inhibition (64.52 %) for A. niger, while Pseudomonas fluorescens exhibited highest inhibition (53.74 %) for A. flavus. Eleven botanicals at 20 % concentration were tested and Allium sativum (garlic) demonstrated complete inhibition (100 %) against both A. niger and A. flavus. In growth promotion studies, it was observed that the pure culture of T. asperellum, when applied to cucumber seeds, resulted in the highest germination percentage (93.02 %), with greatest shoot length (18.59 cm) and the longest root length (6.67 cm). Overall, the study demonstrates that T. asperellum, A. sativum extract and selected fungicides can effectively manage seed-borne Aspergillus spp. while promoting cucumber seedling growth, highlighting their potential for integrated disease management strategies.