Fungicidas microbiológicos e fosfito de potássio na indução de resistência à podridão cinzenta do caule e na fluorescência da clorofila a de soja

Abstract

Gray stem rot can significantly reduce the yield of soybeans and other crops, particularly in low-humidity, high-temperature environmental conditions. Due to the diversity of hosts of this pathogen, the difficulty of controlling the disease, and the possibility of using biological control agents to be promising for soybean, the objective of this work was to evaluate the effect of microbiological fungicides and their mixtures on the photochemical efficiency and control of M. phaseolina in soybean plants. In a greenhouse and the Laboratory of Agricultural Microbiology and Phytopathology, two independent assays were carried out at the Federal University of Grande Dourados, in Dourados-MS. Essay I: 24 treatments were carried out in 4 x 6 factorial (soybean cultivars x disease control treatments) with 4 replications. Two controls were used, one without inoculation and treatment and the other inoculated with the pathogen and without treatment. The cultivars used were M 6210, M 6410, CZ 26B36, and TEC 7022. The commercial microbiological products used were Trichodermil® SC 1306 (Trichoderma harzianum), Tricho-Turbo® (Trichoderma asperellum) and Serenade® (Bacillus subtilis). The commercial fertilizer, composed of potassium phosphite, was FosTec 40 20®. The inoculation of the pathogen was carried out using the toothpick method. Assay II comprises 24 treatments in 2 x 12 factorial (cultivars x disease control treatments) with 4 replications. The cultivars used were M 6410 and TEC 7022. The treatments consisted of the same microbiological products and the commercial fertilizer used in Assay I, adding the treatments of mixtures/combinations between these products. Control of soybean gray rot was not detected with the use of microbiological fungicides based on T. harzianum, T. asperelum, B. subtilis, and potassium phosphite foliar fertilizer. The inoculation of the pathogen caused a decrease in photochemical potential quantum efficiency in photosystem II (Fv/Fm) and the efficiency of absorbed energy conversion (Fv/F0) in untreated plants.