ANTAGONISM BY Penicillium sp. AGAINST Phytophthora capsici (Leonian)

Abstract

Pepper (Capsicum annuum) wilting is caused by a complex of soil pathogenic fungi, among which Phytophthora capsici (Leonian) causes losses in fruit yield from 10 to 100 %; however, there are suppressing soils containing microorganisms such as Penicillium sp., antagonistic to the oomycete. With this background, both microorganisms were collected in the field, mostly at the Bajío region of Guanajuato, México , to identify possible molecular variability between strains of the isolated microorganisms and the relationship with their antagonistic action. Both in vitro and in vivo antagonistic effects of selected isolates of Penicillium spp. over the P. capsici strain identified as the most aggressive, as well as the mode of biological control of the antagonist were determined. The grouping of Penicillium strains did not coincide with their antagonistic action over P. capsici (distant groupings exerted similar antagonistic action), although the aggressiveness of P. capsici was associated with a group in which different restriction enzymes (Hha I, Hinf I and Hae III) did not detect polymorphisms. Out of the 47 Penicillium spp and the seven P. capsici strains obtained, 30 of the antagonist were selected for in vitro confrontation to the most aggressive P. capsici strain. Based on results of this assay, nine antagonists were selected for the in vivo confrontation, of which six isolates stood out in this test, allowing only 5 to 21 % infection, in comparison to 85 % infection of the control inoculated with the pathogen in the absence of antagonists. The antagonistic effect was a combination of inhibition by antibiosis, competition for space, and disintegration of mycelium.