Colletotrichum siamense como estratégia de controle biológico da antracnose em guaranazeiro

Abstract

Brazil stands out in the world market for being the only exporter of guaraná on a commercial scale. The culture of guarana is of great importance for the economy of Amazonas, both from an economic and social point of view. Despite the Amazon region being the center of origin of the plant, in recent years the production of guaraná has declined. Among the factors that have led to this reality, the disease called anthracnose caused by Colletotrichum spp. The use of endophytic microorganisms has been considered a viable alternative due to their ability to protect the plant against the attack of phytopathogens. Furthermore, studies with fungi infected with mycoviruses have drawn attention to its potential use as a biological control agent. Thus, this work aimed to use the fungus Colletotrichum siamense, isolated as an endophytic from guaraná leaves and infected with mycovirus, as a biological control agent for anthracnose in guaraná. The influence of the fungus on physiological and morphological characteristics of the seedlings was also evaluated. To evaluate the in vivo inhibition potential, cuttings of the cultivar BRS-Ceriçaporanga and seedlings of the cultivar Maués were used. The experiment was conducted in two stages. In the first one, the fungus was inoculated by rooting cuttings of the BRS-Ceriçaporanga cultivar. After the period for the establishment of C. siamense, a suspension of conidia of the phytopathogen C. fructicola was sprayed on the seedlings. The seedlings were evaluated for the percentage of characteristic lesions of the disease during 28 days. Morphological analyzes were performed using fresh and dry mass, height and length of the aerial part and root system as parameters. Leaflets from all treatments were analyzed for the presence of macro and micronutrients. In the second stage, the endophyte was sprayed directly on the aerial parts of seedlings of cultivar BRS-Maués. After the period of establishment of the fungus, the phytopathogen was sprayed and the seedlings were observed for 28 days. Leaflets from all treatments were collected at times 0h, 48h, 72h and 96h to measure total proteins, peroxidase (POX), phenylalanine ammonia-lyase (PAL) and chitinase (CHI). The results of the first stage showed that the inoculation of C. siamense in guaraná seedlings helped in reducing the percentage of lesions. In addition, the presence of the fungus helped in the vegetative growth of the plant, reflecting the increase in the aerial part. Significant differences were found in the levels of macro and micronutrients in leaf tissues. The results of the second stage also showed a potential for inhibition of lesions when C. siamense was inoculated in the seedling stage. The presence of the endophyte promoted the synthesis of total proteins and enzymes at different times after inoculation of the phytopathogen. At 48 and 72 hours, the seedlings with the endophyte showed higher POX production. After 72 hours, there was a decrease in the production of this enzyme in all treatments. PAL activity increased after 48 and 72 h. There was no trend in CHI production when compared to other enzymes. Additional studies are needed to optimize the experimental conditions and validate the potential of C. siamense for biocontrol in guarana seedlings.