RESUMO The use of nanoparticles (NPs) in agriculture represents an important technological innovation, which can be employed in the production of nanofertilizers, nanocides or pesticides encapsulated in nanoparticles for controlled release. Silver NPs are recognized for their applications in agriculture, biotechnology and medicine. The objective of this paper was to study the synthesis of silver nanoparticles by endophytic Fusarium concolor obtained from guaraná leaves and seeds, as well as to evaluate the antifungal activity of silver nanoparticles on the in vitro control of the phytopathogens Colletotrichum guaranicola, Colletotrichum spp. and Corynespora cassiicola. Four endophytic Fusarium concolor isolates were used to produce silver nanoparticles. Characterization of NPs was performed by UV-Vis spectroscopy and scanning electron microscopy (SEM). The mycelial growth of phytopathogens in the presence of AgNPs was evaluated in vitro, evidencing antifungal activity, especially against Colletotrichum guaranicola, which suggests that biosynthesized silver nanoparticles can be used in the management of phytopathogens as an alternative to control diseases.

ABSTRACT O uso de nanopartículas (NPs) na agricultura, representa uma importante inovação tecnológica, utilizada na produção de nanofertilizantes, nanocidas ou pesticidas encapsulados em nanopartículas para liberação controlada. As NPs de prata são reconhecidas por suas aplicações na agricultura, biotecnologia, medicina. Este trabalho teve como objetivo estudar a síntese de nanopartículas de prata por Fusarium concolor endofíticos obtidos de folhas e sementes de guaranazeiro e avaliar a atividade antifúngica das nanopartículas de prata no controle in vitro dos fitopatógenos Colletotrichum guaranicola, Colletotrichum spp. e Corynespora cassiicola. Quatro isolados de Fusarium concolor endofíticos foram utilizados para a produção de nanopartículas de prata. A caracterização das NPs foi realizada por espectroscopia de UV-Vis e microscopia eletrônica de varredura (MEV). Foram avaliados crescimento mycelial dos fitopatógenos na presença das AgNPs in vitro e foi observado evidenciando atividade antifúngica principalmente contra o fitopatógeno Colletotrichum guaranicola, sugerindo a possibilidade de utilização de nanopartículas de prata biossintetizadas manejo de fitopatógenos como uma alternativa no controle de doenças.

Resumen La antracnosis de la planta de guaraná (Paullinia cupana) es una enfermedad causada por Colletotrichum guaranicola Albuq. Pocos estudios han analizado el origen, la forma de penetración y la colonización de hongos endofíticos en la planta de guaraná. El presente estudio tuvo como objetivo determinar las diferencias en las actividades enzimáticas de cepas endofíticas y patogénicas de C. guaranicola durante el proceso de infección inicial en hojas de clones sensibles a la antracnosis de guaraná. Se aislaron 14 cepas patogénicas y nueve endofíticas de C. guaranicola desde hojas de guaraná con y sin síntomas de antracnosis, respectivamente. Se evaluaron la actividad enzimática de proteasa, amilasa, polifenol oxidasa, lipasa, pectinasa y la actividad celulolítica para cada cepa del hongo. El diseño experimental para cada ensayo enzimático fue completamente al azar con cinco repeticiones. La evaluación enzimática se basó en la medición del halo de reacción enzimática formada en cada ensayo. Se evaluaron las conidias durante su germinación y formación de apresorios. Los resultados no detectaron diferencia enzimática entre las cepas potogénicas y endofíticas. Los datos previos a la germinación mostraron diferencias entre las cepas endofíticas y potogénicas. La colonización de los tejidos de la planta por cepas patogénicas se evidenció tras la aparición de síntomas de la enfermedad después de 48 horas de la inoculación (hdi), mientras que para las endofíticas se observó la presencia de apresorios en la superficie de la epidermis 48 hdi y no se observó la colonización de las células.

Summary Anthracnose of the guarana plant (Paullinia cupana) is a disease caused by Colletotrichum guaranicola Albuq. Few studies have analyzed the origin, the form of penetration and the colonization of endophytic fungi in the guarana plant. This study aimed to determine differences in the enzymatic activities of endophytic and pathogenic strains of C. guaranicola during the initial infection process in leaves of clones sensitive to guarana anthracnose. Fourteen pathogenic and nine endophytic strains of C. guaranicola were isolated from guarana leaves with and without anthracnose symptoms, respectively. The enzymatic activities of protease, amylase, polyphenol oxidase, lipase, pectinase, and cellulolytic activities were evaluated for each fungal strain. The experimental design for each enzymatic assay was completely randomized with five replicates. The enzymatic evaluation was based on the measurement of halo produced by the enzyme reaction in each assay. Conidia were evaluated during germination and appressoria formation. Results did not detect enzymatic difference between pathogenic and endophytic strains. Data prior to germination showed differences between endophytic and pathogenic strains. Colonization of plant tissues by pathogenic strain was evidenced after the appearance of disease symptoms 48 hours after inoculation (hai), while for endophytic strains the presence of appressoria was observed on the surface of the epidermis 48 hai, and colonization of cells was not observed.

Foi detectada a variabilidade genética de vinte isolados de Colletotrichum guaranicola (Albuq.) provenientes de diferentes localidades produtoras de guaraná no Amazonas, utilizando-se marcadores moleculares AFLP. Foi possível separar os isolados em dois grupos. O coeficiente de variação genética entre os isolados foi de 0,0216 e a similaridade genética foi de 94,95%, confirmando que os isolados pertencem à mesma espécie, no entanto, foi observada variabilidade intra-específica.

The genetic variability of twenty Colletotrichum guaranicola (Albuq.) isolates from different fields of guarana in Amazonas, was studied using molecular AFLP markers. The isolates were separated into two groups. The genetic variability coefficient was 0.0216 and the genetic similarity was 94.5%, confirming that the isolates belongs to the same species, however, an intra-specific variability was observed.