Molecular and morphological characterization of Moniliophthora roreri isolates from cacao in Ecuador

Moniliophthora roreri - the causal agent of frosty pod rot (FP) disease-is one of the most devastating cacao pathogens in Ecuador and worldwide. The centre of diversity of this pathogen is believed to be in areas near Ecuador or Colombia but molecular, morphological and growth studies of this pathogen in Ecuador are scarce. Monosporic cultures of M. roreri from the six cacao-producing regions of Ecuador, including Esmeraldas, El Oro, Los Rios, Guayas, Manabi and Amazon were obtained. Morphological characteristics, such as mycelial growth, colony shape, colour and texture, as well as type and size of meiospores, were recorded for each isolate. Molecular variation was assessed by direct sequencing the ITS1, 5.8 s, and ITS2 rDNA regions as well as by RFLP analyses on the same regions. Results showed little variation of morphological traits across isolates. Mycelial growth rate fitted to a Gompertz model with parameters estimates that were significantly affected by mycelial colour. Molecular analysis data showed an average polymorphism of 48.98% and Shannon's diversity index of 0.21. Multiple discriminant analyses carried out on the RFLP patterns showed a 100% accurate grouping by both sampling province and mycelial colour.