EFEITO DO DESLINTAMENTO QUÍMICO SOBRE A OCORRÊNCIA E DESENVOLVIMENTO DE Colletotrichum gossypii ASSOCIADO ÀS SEMENTES DE ALGODOEIRO*

Effects of chemical delinting on the level of occurrence and development of Colletotrichum gossypii associated with cotton seeds The present work was conducted in two phases. The first phase evaluated how the lenght of time of chemical delinting, 1:30 and 4:30 min, effected the level of infection by Colletotrichum gossypii on artificially inoculated cotton (Gossypium hirsutum) seeds. Non-delinted cotton seeds were artificially inoculated with C. gossypii by by contact with fungal colonies in Petri dishes for 30 h. The parameters evaluated were quality of health and the germination ratio. The second phase aimed at evaluating the influence of cotton seed exudates on the development of C. gossypii in function of the chemical delinting time with sulphuric acid, considering the sedimentation fractions in water and artificial aging periods of 0, 72 and 96 h in laboratory conditions. comercial concentrado pelos períodos de 1:30 e 4:30 min, separadas em frações de sedimentação em água e submetidas ao envelhecimento artificial por 0, 72 e 96 h. Os substratos foram obtidos a partir do exsudato resultante da embebição contendo os eletrólitos lixiviados das sementes. O desenvolvimento de C. gossypii na presença do exsudato das sementes foi avaliado em meio agarizado, através da medição do crescimento micelial e da esporulação do fungo. O deslintamento químico, pelo período de 1:30 min, propiciou aumento do percentual de ocorrência de C. gossypii em sementes nãodesinfestadas superficialmente, e o crescimento micelial e a esporulação do fungo foram favorecidos pelo substrato proveniente de sementes deslintadas por 4:30 e 1:30 min, respectivamente. Palavras-chave adicionais: inoculação artificial, esporulação, crescimento micelial. The seeds were delinted with sulphuric acid for 1:30 and 4:30 min, separated into sedimentation fractions in water and submitted to artificial aging for 0, 72 e 96 h. The substracts were obtained from the exudates containing the electrolytes leaked from the cotton seeds. The development of C. gossypii in seed exudates was evaluated in agar medium, measuring the mycelial growth and sporulation of the fungus. The results showed that chemical delinting for 1:30 min provided an increase in the incidence of C. gossypii in seeds, without superficial disinfestation. The mycelial growth and sporulation of the fungus were favoured on the substracts containing exudates of delinted seeds for 4:30 and 1:30 min, respectively.