Bean seed (Phaseolus vulgaris L.) type "granja asturiana" disinfection with fungicides and bactericides.
Several disinfectant products for seeds (visually with and without disease symptoms) of bean (P. vulgaris) were evaluated in order to obtain healthy bean seeds to be used for sowing. The products tested as fungicides were general disinfectants (such as bleach and oxygenated water) and specific fungicides (captan, thiram, benomyl, thiabendazole, copper, PCNB (quintozene), etridiazole and KMnO4) and as antibacterials (kasugamycin-copper, streptomycin and Copac E [copper sulfate]). The efficacy assays were carried out in the laboratory and then contrasted with a field study. The disinfectant efficacy was evaluated in terms of the number and type of species and colony forming unit number of the different species of fungi recovered from the treated bean seeds and the detection of Pseudomonas syringae pv. phaseolicola [P. savastanoi pv. phaseolicola] by an ELISA-DAS test, as well as by the phytotoxicity of the treatment (germination power of the treated seeds vs. the control). The most relevant findings were: (i) two products, the quintozene and etridiazole mixture and the bleach, were highly phytotoxic, (ii) the most efficient fungicide was thiram, followed by benomyl, and (iii) the presence of Pseudomonas syringae pv. phaseolicola in seeds treated with kasugamycin-copper or streptomycin was much lower than with Copac and the control. The results from the fungicides led us to propose the treatment with thiram (1.5 g/kg of seed) as an efficient disinfectant treatment but the results from the antibacterials do not enable us to make a choice for treatment. The results from this study led us to propose the selection of healthy seed by procedures of pathogen-exclusion as an alternative to chemical antibacterial treatment.