Bactérias: Uso no biocontrole da antracnose e na promoção do crescimento do guaranazeiro [Paullinia cupana Kunth var. sorbilis (Mart.) Ducke]

Abstract

Guaraniculture has economic and social importance in Brazil, as it is the main producer of guarana in the world in commercial terms. The guarana tree is a species native to the Amazon with great importance for the socioeconomic sector of the region. It is found mainly in the Maués region, where it is cultivated by indigenous and traditional communities. Despite their constant genetic improvement, some cultivars present difficulties in rooting cuttings, which directly implies the production of seedlings, in addition to the high incidence of fungal diseases. As an alternative to minimize this problem, the use of endophytic and rhizospheric microorganisms has been efficient in the biocontrol of phytopathogens and in promoting plant growth, and can be used as bioinoculants. Results from previous studies have already shown success with microbial inoculants in legumes and grasses, however little data exists for tropical fruit trees, especially in the production of seedlings. This work aimed to evaluate the action of Amazonian microorganisms in controlling the phytopathogen Colletotrichum fructicola and in the rooting of the guarana tree by promoting plant growth. To evaluate the promotion of plant growth, the bacteria were inoculated via rooting of cuttings in the BRS-CG611 cultivar and through seed microbiolization at concentrations of 1x108 UFC mL-1 and 1x109 UFC mL-1 and planted in a specific substrate. In the biocontrol of anthracnose, the effectiveness of Burkholderia sp. endophytic bacteria isolated from Himatanthus sucuuba, was evaluated by brushing the bacterial suspension at times 72h, 48h, 24h and on the same day of inoculation of the phytopathogen. The highest percentage of rooting of cuttings with the BRS-CG611 cultivar was promoted by the rhizobacteria Bacillus sp. RZ2MS9, however, there was no increase in the root system of the cuttings. Regarding seed germination, the bacteria did not influence the growth of the seedlings. To control the phytopathogen, the inoculation of the endophytic bacterium Burkholderia sp. in guarana seedlings of the BRS-Amazonas cultivar, it suppressed the appearance of the disease in the times that preceded the inoculation of the phytopathogen and reduced the lesions caused by C. fructicola in the seedlings inoculated at time 0h in relation to the control.