Field application of bio-control agents and aqueous plant extracts for controlling bacterial soft rot and enhancement yield quality of Solanum tuberosum L. cv. Diamond

Abstract

Abstract Background Application of chemical bactericides, for controlling soft rot bacteria, causes environmental pollution and toxic hazards to human. In addition, it is ineffective, expensive, and limited. Therefore, application of bio-control agents, plant extracts, or safe chemicals may play an important role as safe alternative approaches for controlling phyto-pathogenic bacteria. Objective This work is aimed to apply bio-control agents (Bacillus subtilis, Bacillus pumilus, Trichoderma harzianum, and Trichoderma virens), aqueous plant extracts (lantana flowers and leaves, lemongrass leaves, and olive cake), and citric acid as pre-sowing treatment for controlling bacterial soft rot pathogen and study their ability for improving yield and quality of potato tubers in field and storage. All treatments were applied as soil treatment and/or foliar spray, except citric acid applied as foliar spray only. Results The cultural filtrates of bio-control agents of B. subtilis, B. pumilus, T. harzianum, and T. virens; aqueous plant extracts of lantana, lemongrass, and olive cake; and citric acid could protect daughter potato tubers against bacterial soft rot disease in field application, except lemongrass (as soil treatment). The bio-control agents highly increased the activities of peroxidase, polyphenol oxidase, and chitinase enzymes, than other treatments. The bio-control agents also improved the shoot parameters, viz, shoot length, number of shoots/pit, and number of leaves/pit and yield parameters, viz, tuber weight/pit, tubers number/pit, and total tubers weight/pit, compared to citric acid and plant extracts, respectively. The treatments as foliar spray have good results for protecting the potato tubers through storage, than soil treatment. The treatments highly enhanced the stored potato tubers quality, viz, dry matter, reducing sugars, total carbohydrates, specific gravity, and starch content. Conclusions The tested treatments could protect the potato tubers in field and/or storage against soften development. The treatments could improve the plant growth and yield parameters in field as well as enhanced the stored potato tubers quality and increase the stored time. It is clear that the treatments can be applied as pre-sowing treatment for controlling Erwinia soft rot bacteria.