Inhibitory Effect of CUSTOS, a Formulated Allium-Based Extract, on the Growth of Some Selected Plant Pathogens

Abstract

Plants are in intimate association with a great diversity of pathogenic and mutualistic microbes that use host plants for proliferation. Plants, in turn, have evolved mechanisms that are contingent upon their innate immune system to resist perceived biotic stresses. The objective of this work is to determine the antimicrobial properties of an allium-based antimicrobial formulation named CUSTOS on the growth of plant pathogenic microorganisms such as fungi, oomycetes, and bacteria. Two anthracnose-related species of the fungal genus Colletotrichum, Colletotrichum gloeosporioides, the oomycete Phytophthora cactorum, and the bacterium Xanthomonas fragariae associated with strawberry plants were tested in vitro. Furthermore, two fungi Alternaria dauci and Botrytis cinerea, associated with carrot plants, were tested in planta. CUSTOS inhibited the growth of all plant pathogens tested. We found that both curative and preventive planta treatments with CUSTOS inhibited the growth of Alternaria dauci and Botrytis cinerea in carrots. Furthermore, the differential expression levels of the PR 10 genes were correlated with the magnitude of infection. We also found that the field application of CUSTOS on strawberry plants results in a reduction of fungal pathogens on strawberry fruits stored under refrigeration. In summary, CUSTOS may induce pathogen resistance in fruit and vegetable plants and can be used as both a curative and a preventive against rotting and disease.