Green pepper (Capsicum annum) sclerotium wilt, caused by Sclerotium rolfsii, is one of the most important diseases of this solanaceous in tropical regions. One of the basic requirements for successful in controll of this disease is knowledge of the pathogen, especially of factors related to physiology and biology. The present work aimed to characterize five isolates of S. rolfsii (SR1, SR2, SR3, SR4 e SR5), from green pepper, accessing the mycelial growth, sclerotia production in different photophases and in six natural substracts and the vegetative compatibility among these isolates. The substract effect varied within isolates for sclerotia production. The SR3 and SR5 presented the highest sclerotium production in oat (Avena sativa)-agar (OA) and flour-agar (CA), SR1 in rice (Oryza sativa) hull (RH), SR2 in OA and SR4 in CA. The RH favored sclerotia formation in most isolates. For the mycelial growth rate, the isolates tested showed low variation, but SR1, SR2 and SR3 presented higher growth. The five isolates showed differential behavior when submitted to three different photophases: continuous light (CL), alternating light and dark (L/D) and continuous dark (CD), the highest sclerotia production was found under CL. The vegetative compatibility test showed genetic diversity among the five isolates, clustering them into three groups. The SR3 and SR5 were incompatible one to other and with all other isolates. There was vegetative compatibility among isolates SR1, SR2 and SR4. According to the biological and physiological aspects studied the isolates of S. rolfsii SR3 and SR5 can be considered different "strains", while SR1, SR2 and SR4 belong to the same strain.
Capsicum annum; Sclerotium sp.; sclerotia production; vegetative compatibiliy
