Comportamento de genótipos de crambe (Crambe abyssinica Hochst) inoculados com Sclerotinia sclerotiorum

Abstract

The objectives of this work were to evaluate the reaction of Crambe abyssinica genotypes inoculated with Sclerotinia sclerotiorum, using three inoculation methods (toothpick, mycelial disc in detached leaf and leaf axil), to verify the pathogen transmission by C. abyssinica seeds inoculated artificially, and to evaluate the pathogen relation and involvement on seedling emergence. The experiments were conducted in two different environments (greenhouse and Phytopathology Laboratory). C. abyssinica and soybean (used as reference) seeds were sowed in pots containing 4 kg of soil, sand and Bioplant substrate (1:1:1), cultured for three months in a greenhouse, and inoculated 60 days after emergence (DAE), in order to evaluate the different methods of inoculation. The disease severity was evaluated daily until the lesion reached the whole plant. The mycelial disc inoculation method in detached leaves had evaluations from 48 hours after inoculation, according to a diagrammatic scale. The C. abyssinica lineage FMSCR 1101 presented greater amount of S. sclerotiorum. Different genotypes of C. abyssinica (FMS Brilhante, Mario, Galactica and FMSCR 1101) were sowed in pots containing 1.3 kg of the described substrate for evaluation. The three inoculation methods were performed 29 DAE and evaluations began 48 hours after inoculation. The mycelial disc inoculation method in leaf axils presented more lesion progress in the genotype FMS Brilhante and the genotype Mario was the most resistant. This inoculation method allowed a better evaluation of the resistance of C. abyssinica genotypes to the pathogen. Seeds were placed in Petri dishes colonized by the fungus for 20 hours, and 250 seeds per treatment (inoculated and non-inoculated) were sowed in plastic trays containing the described substrate, to evaluate the transferability of the fungus via C. abyssinica seeds. The fungus pathogenicity to the genotypes was assessed by counting the emerged seedlings with and without symptoms, which was performed 9 and 18 days after sowing (DAS). The transmission confirmation was performed by the Neon S method, 22 DAS. The pathogen can be transmitted to seedlings when associated with seed, which is an important source of inoculum.