Abstract
Fifty four Trichoderma strains were isolated from soil samples collected from garlic and onion crops in eight different sites in Brazil and were identified using phylogenetic analysis based on combined ITS region, tef1-α, cal, act and rpb2 sequences. The genetic variability of the recovered Trichoderma species was analysed by AFLP and their phenotypic variability determined using MALDI-TOF. The strain clusters from both typing techniques coincided with the taxonomic determinations made from phylogenetic analysis. The phylogenetic analysis showed the occurrence of Trichoderma asperellum, Trichoderma asperelloides, Trichoderma afroharzianum, Trichoderma hamatum, Trichoderma lentiforme, Trichoderma koningiopsis, Trichoderma longibrachiatum and Trichoderma erinaceum, in the soil samples. We also identified and describe two new Trichoderma species, both in the harzianum clade of section Pachybasium, which we have named Trichoderma azevedoi sp. nov. and Trichoderma peberdyi sp. nov. The examined strains of both T. azevedoi (three strains) and T. peberdyi (12 strains) display significant genotypic and phenotypic variability, but form monophyletic clades with strong bootstrap and posterior probability support and are morphologically distinct from their respective most closely related species.
Highlights
One of the most important fungal diseases occurring in garlic (Allium sativum) and onion (Allium cepa) is white rot, caused by the sclerotium-forming fungus Sclerotium cepivorum, often causing severe losses in garlic and onion production worldwide [1]
Fifty four Trichoderma strains were isolated from soil samples collected from garlic and onion crops in eight different sites in Brazil and were identified using phylogenetic analysis based on combined ITS2 region (ITS) region, tef1-α, cal, act and rpb2 sequences
Confident and unambiguous species identifications were not obtained in the searches, as expected, since previous studies have pointed out the limitations of ITS sequences to delimit Trichoderma species [23]
Summary
One of the most important fungal diseases occurring in garlic (Allium sativum) and onion (Allium cepa) is white rot, caused by the sclerotium-forming fungus Sclerotium cepivorum, often causing severe losses in garlic and onion production worldwide [1]. In Brazil, the states of Parana, Minas Gerais, São Paulo and Goias produce 64% of the national Allium crop (mostly garlic and onion) [2]. Despite recent advances in Allium production in Brazil, production is not sufficient to fulfil internal demand, due to low productivity [3]. Despite the diversity of garlic and onion cultivars available to growers, the favorable humidity and temperature conditions for most of these cultivars are conducive to white rot disease. In the absence of reliable conventional white rot control methods, biological control is being investigated as a viable option, using species of the fungal antagonist, Trichoderma [4].
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