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Biological control of southern blight (Sclerotium rolfsii L.) on beans (Phaseolus vulgaris L.) with Trichoderma harzianum R. and three bio-preparations as a soil amendment and seed treatment

University of El Salvador, Fac. of Agronomic Sciences, El Salvador

Abstract

This research was conducted in the laboratory and greenhouse of the Department of Plant Protection of the Faculty of Agricultural Sciences of the University of El Salvador, during the months of March to May 2017. The effectiveness of three bio-preparations (lombriabono, bokashi, and mountain microorganisms), an antagonist Trichoderma harzianum (Excalibur Gold®), a relative control (Copper Hydroxide, (Kocide WG ®), and absolute control (no treatment); and two methods of application (soil amendment and seed pelleting), on pathogenic fungus Sclerotium rolfsii L., which causes Southern blight disease in bean cultivation. The assay was conducted under greenhouse conditions with 11 treatments and 5 repetitions, plus a duplicate of the assay. The observations were carried out from planting to the first month, which is the critical stage of infection by the pathogen, inoculating the pathogenic fungus in the sterile substrate, taking emergency data 5 days after planting the bean, and then every 3 days to measure the level of infection. The data collection was done by the presence of signs of the pathogen and symptoms of the disease, the emergence, and infection in seed, and plant infection was evaluated.
The methods of application had an influence on the control of infection by Sclerotium rolfsii L. in seed (χ1=93.96% P=2.2×10-16). Where the lowest percentage of probability was obtained by soil amendment (2.5%, EE=0.60), demonstrating that this practice reduces the effects of the pathogen on bean seeds. The evaluation for the application only of the products, showed differences for the infection to the seed (χ4=62.52, P<8.55×10^-13) for which it can be concluded that the treatments with biological products do influence the behaviour and development of the pathogen since the existing microbial activity can inhibit or potentiate the development of infections. For the interaction of the products only as pelleted to the seed was T. harzianum (Excalibur Gold FS®) which presented a lower percentage of infection in the seed (4.5% EE=3.2%). There were strong effects of interaction between products and forms of application, for emergencies (X4=48.921 P= 6.066×1010), infection in seed (χ4=32.894 P=1.256×10⁶), and plant infection (χ4=15.6784 P=0.00348).

Keywords: Phaseolus vulgaris, Sclerotium rolfsii, Trichoderma harzianum

Contact Address: Yesenia Marisol Guardado Torres, University of El Salvador, Fac. of Agronomic Sciences, CP 1502 Antiguo Cuscatlan, El Salvador, e-mail: marisol.guardadotgmail.com