Revista Brasileira de Milho e Sorgo (Aug 2002)
MOLLICUTES AND VIRUSES ON MAIZE AT THE “SAFRINHA” GROWING SEASON AND AT THE “SUMMER” GROWING SEASON.
Abstract
The incidence of Corn stunt diseases symptoms and virus infection symptomswas surveyed on 22 cultivars sowed in the “Safrinha” growing season and in the “Summer”growing season at several localities in São Paulo, Goiás and Minas Gerais States. These surveywas made from Safrinha 1999 until Safrinha 2000. Leaves samples from plants with Corn stuntdiseases symptoms were submitted to DNA extraction and to PCR test to determine theincidence index of infection by phytoplasma and by spiroplasma. Leaves samples with virusinfection symptoms were submitted to RT-PCR to confirm the virus identification. In general, the incidence of Corn stunt diseases symptoms was higher in the Safrinha growing season thanin the Summer growing season, except in São Paulo state where the incidence of these diseaseswas similar on both seasons. The mollicute infection was detected in 103 samples, among 390submitted to PCR test. The simultaneous infection by both spiroplasma and phytoplama wasdetected only in 6 samples. Taken into account the total of positive samples to mollicute infection,the incidence of spiroplasma and phytoplasma was similar. However, only in the Safrinha growingseason it was observed that only one of these mollicute predominated. This predominancealternated from spiroplasma in Safrinha 1999, to phytoplasma in Safrinha 2000 and spiroplasmain Safrinha 2001. The Maize Rayado Fino Virus (MRFV) and the Maize Dwarf Mosaic Virus(MDMV) were detected in variable levels of incidence, just at some localities and growingseason evaluated, in general with incidence levels lower than the ones of Corn stunt diseases.