Expression of MfAvr4 in banana leaf sections with black leaf streak disease caused by Mycosphaerella fijiensis: a technical validation

The objective of this study was to validate the use of banana leaf sections as a technique to study the molecular interaction between Mycosphaerella fijiensis and Musa spp. without the interference of biotic and abiotic factors that commonly occur under field conditions. The growth of M. fijiensis in banana leaf sections was evaluated and compared with the growth of the fungus in leaves under field conditions. Growth comparison was carried out through the absolute quantification by real-time PCR of a segment of the β-tubulin gene of M. fijiensis. Validation of the banana leaf sections technique consisted in monitoring M. fijiensis MfAvr4 gene expression and its relative quantification by real-time PCR in banana leaf sections. With this technique, it was shown that the growth of M. fijiensis and MfAvr4 gene expression were similar to those observed in infected leaves in the field. These quantitative real-time PCR results support the suitability of using banana leaf sections for molecular studies of gene expression in M. fijiensis-Musa spp. interactions.