Abstract Yerba mate (Ilex paraguariensis) crop is susceptible to many disease-causing agents that affect a plant, like a root rot, reducing its productivity. The present study aimed to evaluate the in vitro antagonist potential of Trichoderma sp. on Fusarium oxysporum, the causal agent of root rot in yerba mate. Four Trichoderma spp. isolates and one Fusarium oxysporum isolate were used. The antagonistic action of Trichoderma spp. on F. oxysporum was evaluated through the dual cultures and volatile metabolites tests. The results of the dual cultures assay revealed that Trichoderma spp. inhibited the mycelial growth of Fusarium oxysporum, with percent inhibition ranging from 13.06 to 14.24%. Moreover, in the volatile metabolites test, T. tomentosum and T. harzianum showed the best inhibition results, 27.70 and 24.46%, respectively. Thus, Trichoderma spp. presented in vitro antagonist potential in the control of Fusarium oxysporum.

Resumo A cultura da erva-mate está exposta a doenças que prejudicam o desenvolvimento da planta, reduzindo a produtividade. Dentre essas doenças têm-se a podridão-de-raízes causada por Fusarium spp. O objetivo deste trabalho foi avaliar a ação antagonista in vitro de Trichoderma spp. sobre Fusarium oxysporum, agente causal da podridão-de-raízes em erva-mate. Foram utilizados quatro isolados de Trichoderma spp. e um isolado de Fusarium oxysporum. A ação antagônica de Trichoderma spp. sobre F. oxysporum foi avaliada por meio do teste de pareamento de culturas e de metabólitos voláteis. No teste de pareamento de culturas, os isolados de Trichoderma spp. inibiram o crescimento micelial de Fusarium oxysporum, com percentual de inibição que variou de 13,06% a 14,24%. No teste de metabólitos voláteis, T. tomentosum e T. harzianum apresentaram os melhores resultados de inibição, com 27,70% e 24,46%, respectivamente. Assim, pode-se concluir que Trichoderma spp. apresenta ação antagonista in vitro contra F. oxysporum, agente causal da podridão-de-raízes em erva-mate.

ABSTRACT One of the limiting factors for pecan production is the incidence of disease caused by Fusarium spp. which are a threat to orchards in the south of the country. Therefore, the study aimed to confirm the pathogenicity and evaluate the morphophysiological and molecular characteristics of Fusarium spp. associated with pecan in Rio Grande do Sul and Paraná. For this, samples of symptomatic plant material were collected, and potentially pathogenic isolates were evaluated for pathogenicity, by immersing the roots of the plants in a spore suspension of Fusarium spp. In addition, the severity of the disease was assessed using a rating scale according to the symptoms expressed by the plants. The isolates were also analyzed for morphophysiological variability, through evaluations of mycelial growth, colony and aerial mycelium pigmentation, and characteristics of reproductive structures. Molecular characterization was performed which amplify the region of the 1-alpha elongation factor and sequencing. Nineteen isolates were obtained, which were considered pathogenic, however, there was variability in their aggressiveness and morphophysiological characteristics. In addition, the sequencing was used to identify different species. Therefore, species of Fusarium are responsible for the occurrence of wilt in pecan in southern Brazil.

Resumo Juglans regia e Carya illinoinensis, ambas da família Juglandaceae, são espécies de nogueiras conhecidas mundialmente pela produção das chamadas nozes, com crescente expansão da área cultivada na América do Sul. Entretanto, nos últimos anos houve aumento da incidência de doenças nessas espécies, o que compromete a rentabilidade dos cultivos e a qualidade do produto. Colletotrichum nymphaeae foi recentemente identificado no Brasil causando danos em frutos de Juglans regia. Este estudo teve como objetivo avaliar o potencial de infecção cruzada de C. nymphaeae, isolado de frutos sintomáticos de Juglans regia, em folíolos e frutos de cultivares de Carya illinoinensis. Para isso, discos de meio de cultura contendo estruturas do patógeno foram depositados sobre folíolos e frutos de seis e três cultivares de Carya illinoinensis, respectivamente. Colletotrichum nymphaeae mostrou-se patogênico tanto em folíolos como em frutos de todas as cultivares avaliadas, sendo que as maiores lesões em folíolos foram observadas nas cultivares ‘Barton’, ‘Melhorada’ e ‘Imperial’, enquanto que a cultivar ‘Shawnee’ demonstrou menor suscetibilidade ao patógeno. Nos frutos, a cultivar ‘Imperial’ mostrou-se mais suscetível ao patógeno, já que apresentou as maiores lesões.

Abstract Juglans regia and Carya illinoinensis, both from the Juglandaceae family, are species known worldwide for the production of edible nuts, with an increasing expansion of the cultivated area in South America. However, in recent years there was an increase in the incidence of diseases in the species, which compromises the profitability of crops and the nut quality. Colletotrichum nymphaeae was recently identified in Brazil causing damage to fruits of Juglans regia. This study aimed to evaluate the potential for cross-infection of Colletotrichum nymphaeae, isolated from symptomatic fruits of Juglans regia, on leaves and fruits of Carya. illinoinensis cultivars. Disks of culture medium containing structures of the pathogen were deposited on leaflets and fruits of six and three cultivars of Carya illinoinensis, respectively. Colletotrichum nymphaeae was found to be pathogenic both in leaflets and in fruits of all the cultivars evaluated, with the largest lesions in leaflets observed in the cultivars ‘Barton’, ‘Melhorada’ and ‘Imperial’, while the cultivar ‘Shawnee’ demonstrated less susceptibility to the pathogen. In the fruits, ‘Imperial’cultivar was more susceptible to the pathogen, since it presented the largest lesions.