Métodos de inoculação de isolados de Fusarium guttiforme em genótipos de abacaxizeiro ornamental

Abstract

The fusariosis is a disease caused by the fungus Fusarium guttiforme that has been causing damages and losses in the ornamental pineapple (Ananas comosus), in the main producing regions. One of the interesting tactics for disease control is the use of resistants varieties. Therefore, the objective of this study was to select the most efficient method of inoculation of isolates of F. guttiforme, in ornamental pineapple genotypes, to express the disease. To this end, fourteen isolates of F. guttiforme were used and inoculated in micropropagated seedlings of ornamental pineapple of hybrid D (Ananas comosus var. bracteatus × Ananas comusus var. erectifolius) and commercial erectifolius (Ananas comosus var. erectifolius). Two methods of inoculation were tested: a) deposition of mycelium discs in the lap of the plant and b) deposition of infested sticks in a prominent leaflet. In the first inoculation method, 105 seedlings were inoculated, with seven replicates (each replicate = one seedling). The disease evaluations were carried out at 112 days after inoculation, by quantification of disease severity by the descriptive scale of grades (1 to 6). In the second inoculation method, 90 leaflets of ornamental pineapple were inoculated, with three repetitions (each replicate = one detached leaflet), the evaluations were conducted every five days, until the thirtieth day of incubation through the measurements of length and width, obtaining the lesion size. It was concluded that the method of deposition of infested sticks on detached leaves was more efficient for early expression of the disease in ornamental pineapple due to controlled conditions in the laboratory.