Qualidade fisiológica de sementes de algodoeiro e comportamento in vitro de Sclerotinia sclerotiorum (Lib.) De Bary, submetido a diferentes temperaturas

Abstract

Gossypium hirsutum L. is a world wide cultivated species of great economic importance. However, due to outbreaks of diseases such as white mold, caused by Sclerotinia sclerotiorum, is responsible for causing symptoms such as wilting, necrosis and wet rot in the stems. This study aimed to evaluate the effect of temperature on mycelial growth and sclerotia production, identify the incidence of pathogens associated with cotton seeds not inoculated and inoculated with S. sclerotiorum and studying the physiological quality of cotton seeds inoculated and not inoculated with S. sclerotiorum . The experiments were carried out in the Plath Pathology Laboratory (LAFIT) of Universidade Federal of Paraíba (UFPB), in Areia county, Paraíba state. The mycelial growth and sclerotia production and weight at 15, 20, 25 and 30 ºC were evaluated. To evaluate the seed physiological quality of the cotton cultivar Seridó and the incidence of other pathogens associated, 400 seeds were used, with inoculation method by direct contact of the seeds with mycelium and sclerotia. The sanitary quality of seeds was evaluated by the Blotter Test. The physiological quality was determined by the standard germination test and the evaluation of emergency, using sterile sand substrate. The emergency, speed index of emergency, shoot length and root system, the content of motherland dry shoot and root system. Were evaluated. The experimental design was completely randomized and means were compared by Tukey test. There washigher mycelial growth of S. sclerotiorum in temperatures of 20 and 25 ºC. The largest production of sclerotia was in temperatures of 20 and 30 º C (22,20; 24,73). The average weight of sclerotia was higher at 25 and 30 °C (0,19; 0,22 mg). There was no significant effect of inoculation with S. sclerotiorum on the incidence of other pathogens associated iv with seeds. The largest percentage of seedlings and larger length of shoots was observed in cotton seeds not inoculated and higher dry matter content of roots of cotton seedlings was observed in seeds inoculated with S. sclerotiorum