A simple and cost-effective diagnostic of Macrophomina phaseolina on watermelon by direct PCR

Macrophomina phaseolina (Tassi) Goid is the causal agent of charcoal rot and vine decline in cucurbits such as watermelon. Molecular methods have been used for rapid identification. However, a large number of steps used reduces its applicability. This study aimed to detect M. phaseolina in watermelon from producing areas in Northeastern Brazil by direct PCR. Plant tissue samples were collected from seven producing areas and the DNA was extracted using the CTAB method. Amplifications were performed by direct PCR using the MpKFI/MpKRI primers, then the PCR products were subjected to agarose gel electrophoresis and sequenced. Amplicons of 350 bp were observed in stem tissue samples from three areas. The identity of the samples was confirmed by sequencing. This study represents the first molecular diagnosis of M. phaseolina associated with watermelon in Northeastern Brazil. The methodology presented here can be applied for a reliable and simple diagnosis of the pathogen in other crops.