Isolation and identification of antagonists associated with parasitism on Sclerotinia sclerotiorum sclerotia in Tucumán province, Argentina

Abstract

In Northwestern Argentina, bean production constitutes a major agricultural activity. One of the most complex phytosanitary problems affecting this crop is caused by Sclerotinia sclerotiorum, a fungus capable of producing sclerotia that play an important part in the disease cycle. The aim of this work was to isolate and identify native antagonists associated with parasitism on Sclerotinia sclerotiorum sclerotia in Tucumán province, Argentina. The antagonists were isolated using the sclerotia bait technique, and by retrieving them from naturally parasitized sclerotia, in three agrologic regions in the province. Fifty nine isolates were obtained using sclerotia as baits and 3 were recovered from collected sclerotia at fruit and vegetable commercialization centers. Most of the antagonists, specifically 76% of them, were isolated in the foothills region (called “Pedemonte”). The analysis of sequences of the ITS1-ITS2 region and that of the region coding for the translation elongation factor -1α gen (tef1α) revealed that Trichoderma species do not have a homogeneous distribution in the soil types of the evaluation sites. The prevalent Trichoderma species were T. atroviride and T. koningiopsis, both of which belong to the Trichoderma sect., viride clade. Only one isolate of the T. longibrachiatum species was identified, as well as one of T. afroharzianum.