Potential of Biotic and Abiotic Inducers of Eliciting Systemic Resistance in Snap Bean (Phaseolus vulgaris L.) in Controlling Rust Caused by Uromyces appendiculatus

Abstract

The biotic and abiotic inducers of resistance i.e., Bacillus subtilis, Paenibacillus polymyxa, Trichoderma harzianum, Trichoderma viride, ascorbic acid, Bion, potassium citrate, salicylic acid, as well the fungicides i.e., Domark EC 10% and Tilt EC 25%, were evaluated in vitro, and field conditions in both 2019 and 2020 growing seasons to control snap bean rust (Uromyces appendiculatus) at Ashmoun, Menoufia Governorate, Egypt. In vitro results indicated that all the tested bio-agents, chemical resistance inducers and the two fungicides significantly inhibited uredospores germination. The fungicide Domark EC 10% was the best effective treatment followed by Tilt EC 25% fungicide and B. subtilis, where they recorded 97.1, 96.3 and 82.4% inhibition of uredospore germination percentage, respectively, comparing with control treatment. Spraying the tested biotic, abiotic inducers, and the tested fungicides of bean plants under field conditions significantly reduced disease severity of bean rust, Area Under Disease Progress Curve (AUDPC) and rate of disease increase (r-value). Meanwhile, significantly increased performances of growth and yield parameters i.e., plant height, No. of branches/plant, plant fresh and dry weights, pod length (cm), average pod weight/plant (g) and yield (ton/fed), in both 2019 and 2020 growing seasons compared to the untreated control treatment. Meantime, considerable increases were recorded resulted in all the tested treatments in photosynthetic pigments, chlorophyll and carotenoids; activities of peroxidase (PO) polyphenol oxidase (PPO) and Catalase (CA) enzymes; phenol content, i.e., free phenols, conjugated phenols, and total phenols. Furthermore, a remarkable increase was recorded in the green pods chemical composition in protein and carbohydrates content (%) and Nitrogen (N), Phosphorus (P) and Potassium (K) minerals content compared to the untreated control.