Abstract

RIVERA AVALOS, Sergio; MARTINEZ-PENICHE, Ramón Álvar; SOTO-MUNOZ, Lourdes  and  CHAVARO-ORTIZ, María del Socorro. Modes of action four strains of antagonistic yeasts against Penicillium expansum Link in apple. Rev. Chapingo Ser.Hortic [online]. 2012, vol.18, n.2, pp.227-238. ISSN 2007-4034.  https://doi.org/10.5154/r.rchsh.2010.08.030.

The use of antagonistic yeasts to control diseases in postharvest apples reduces environmental risks. Knowing the modes of action of the antagonists is essential in order to use them at a commercial level. Two modes of action of four yeast strains against Penicillium expansum Link were studied. Antibiosis was evaluated by means of dual cultures and antibiograms, and nutrient competition using culture microplates containing semipermeable polytetraflourethylene (PTFE) filters. The absence of inhibition haloes in the dual cultures and in antibiograms showed the antagonists' inability to produce antibiotics. Germination of P. expansum conidia was about 95 % in all of the different growing media in the microplates when antagonistic yeasts were absent. However, it significantly declined (anywhere from 10 to 20 %) in the presence of any of the yeasts. When the yeasts were separated from the fungus by means of the filter, germination of P. expansum only increased significantly with the strain 22-111 (Pichia guilliermondii) in all the media, obtaining a low correlation coefficient for the germination index of both treatments (r = -0.303), which assumes a direct interaction between the antagonist and the fungus. In contrast, with strains 38-432, 24^-2_3a and 22^-2_4a conidia germination was very similar to that obtained when the yeasts were directly in contact with conidia (r = 0,999 and r = 0.995, respectively), which suggests that nutrient competition is their main code of action.

Keywords : Malus domestica Borkh; antagonism; biological control; blue mold; antibiosis; competition for nutrient.

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