RESUMO
Cherry tomato Solanum lycopersicum var cerasiforme cv Matt's wild cherry is a very resistant cultivar to most Phytophthora infestans isolates. Two isolates were identified, US940480 and US970001 that cause an incompatible and a compatible interaction respectively. US970001 is one of the few isolates producing a compatible interaction with this cultivar. To identify genes with a differential gene expression between compatible and incompatible interactions, gene expression patterns were analyzed with tomato cDNA microarrays including 12,899 independent tomato cDNA clones at different time points after inoculation. A diverse set of statistical tools were used to identify key components of the plant response to the pathogen. Forty-three genes were up-regulated during the incompatible reaction at time point 36 hours, 15 globally at all time points and twelve were found both in globally and at 36 hours. Northern blots analysis was performed to confirm differential expression showed by microarray analysis and to study the differential expression of more plant resistance genes (PR) genes between compatible and incompatible interactions for this interaction.
El tomate cherry Solanum lycopersicum var cerasiforme cv Matt's es bastante resistente a la gran parte de aislamientos de Phytophthora infestans. Se han identificado dos aislamientos, US940480 y US970001 que causan interacción incompatible y compatible respectivamente. US970001 es uno de los pocos aislamientos causantes de interacción compatible con este cultivo. Con el fin de identificar genes con expresión diferencial en interacciones compatible e incompatible, analizamos DNA copia de 12899 clones independientes en tres tiempos posteriores a la inoculación del patógeno. Se aplicaron diversas herramientas estadísticas para identificar componentes moleculares claves de la respuesta de la planta al patógeno. Cuarenta y tres genes fueron detectados como activados durante la interacción incompatible a las 36 horas posinoculación, 15 genes se detectaron como activados globalmente tomando en conjunto los 3 tiempos analizados y 12 genes tanto globalmente como a las 36 horas. Análisis de Northern blot permitieron confirmar la expresión diferencial detectada con los análisis de microarreglos y estudiar la expresión diferencial de otros genes de resistencia en plantas (PR) en in teracciones compatible e incompatible en esta interacción.
RESUMO
The population of Phytophthora infestans in Brazil was first characterized 12 years ago. In this research, isolates of P. infestans from potato (n = 184) and tomato (n = 267) collected in southern and southeastern Brazil were characterized to provide more detailed analysis of the current structure of the population. All 451 isolates were analyzed for mating type, and subsets of the isolates were analyzed for allozymes, restriction fragment length polymorphism fingerprint, mtDNA haplotypes, and metalaxyl resistance. Tomato isolates were all of A1 mating type, mtDNA Ib, and US-1 genotype or some variant within this clonal lineage. Of the potato isolates, 82% were A2 mating type, mtDNA IIa, BR-1 genotype, which is a new lineage of P. infestans. All A2 isolates were found on potato, whereas 91% of the A1 isolates were from tomato. A1 and A2 isolates were never found in the same field. The frequency of resistance to metalaxyl was higher in isolates from tomato (55%) than in isolates from potato (38%). After more than a decade of coexistence of isolates of the A1 and A2 mating types, the population was highly clonal, dominated by the BR-1 and US-1 clonal lineages.