Abstract
Melampsora medusae f. sp. deltoidae is causing serious foliar rust disease on Populus deltoides clones in India. In the present study, a novel fungal hyperparasite on M. medusae has been reported. The hyperparasitic fungus was isolated from the uredeniospores of the rust fungi and identified as Cladosporium oxysporum by morphological characterization and DNA barcode technique based on the Internal Transcribed Spacer (ITS) region of nrDNA and beta-tubulin (TUB) gene region. Hyperparasitism was further confirmed through leaf assay and cavity slide methods. Leaf assay method showed no adverse effect of C. oxysporum on poplar leaves. However, the mean germination percentage of urediniospores was significantly decreased (p < 0.05) in the cavity slide method when a conidial suspension (1.5 × 10(7) conidia per ml) of C. oxysporum was applied in different deposition sequences. Scanning and light microscopic observations were made to explore the mode of action of the hyperparasitism. The antagonistic fungus vividly showed three different types of antagonism mechanisms, including enzymatic, direct, and contact parasitism. Alternatively, by screening 25 high-yielding clones of P. deltoides, five clones (FRI-FS-83, FRI-FS-92, FRI-FS-140, FRI-AM-111, and D-121) were enlisted under highly resistant category. Present study revealed an antagonistic relationship between C. oxysporum and M. medusae, which could be an effective method of biocontrol in field plantations of poplar. Combining this biocontrol approach with the use of resistant host germplasm could be an environment friendly strategy for preventing foliar rust and increasing poplar productivity in northern India. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-023-03623-x.