Effect of biotherapic of Alternaria solani on the early blight of tomato-plant and the in vitro development of the fungus

Abstract

Background: homeopathy is a means permitted in organic agriculture to control disease and plagues; biotherapics are a practical means for farmers to intervene on the health of plants in agro-ecological systems of production. Tomato-plants can be affected by several diseases, one of the most significant ones in Brazil is early blight, caused by fungus Alternaria solani, due to the damage it causes and its wide distribution in the country. Aims: to establish whether a biotherapic of A. solani may interfere on the in vitro development of the fungus and whether it affects the severity of early blight on tomato-plants in greenhouse. Methods: the effect of the biotherapic on the fungus was evaluated through the percentage of germinated spores under microscope and the growth of colonies in a culture medium. Treatments used were: biotherapic 26cH, 27cH, 28cH, 29cH and 30cH; sterilized distilled water; and diluted and agitated hydroalcoholic solution. The effect of the biotherapic on the development of disease was evaluated in 4 experiments in greenhouse. Plants were kept in vases and subjected to artificial inoculation of the fungus after the application of treatments. Evaluation of disease was carried out through diagrammatic scale. Results: no treatment affected the germination of spores or the development of fungus colonies in the culture medium. In the first test, treatment 26cH differed from water in Tukey’s test at 5% but did not differed from diluted and agitated hydroalcoholic solution. In the second test, treatments 27cH and 28cH showed significant difference from both water and hydroalcoholic solution with an average control of disease of 57% and 62% respectively. The other 2 tests did nor exhibit any significant effect. Conclusions: there was no direct effect of the biotherapic on the fungus, but there was an effect on the severity of the disease. Factors affecting the efficiency of the biotherapic must be better understood before it can be recommended to farmers for the management of early blight in tomato-plants.