Development of PCR-based assays to diagnose the major fungal pathogens infecting pulse crops, potential for germplasm health certification and quarantine processing

Abstract

Plant diseases cause serious economic losses of agriculture production worldwide. Rapid, accurate and reliable diagnostic methods are required to alleviate the detection of fungal plant pathogens to prevent their spread and achieve effective management. This study was aimed to develop fast, reliable and highly sensitive diagnostics to detect fungal plant pathogens for quarantine processing, safe exchange and conservation of germplasms of pulse crops. Multiplex and real time PCR assays were developed for detection of Rhizoctonia solani, Macrophomina phaseolina, Ascochyta rabiei, Alternaria alternata, A. tenuissima, Fusarium oxysporum f. sp. ciceris, Sclerotium (Athelia) rolfsii, Sclerotinia sclerotiorum, Pseudocercospora cruenta and Cercospora canescens causing various diseases in pulse crops. Twenty-two sets of primers from various genomic regions such as cytochrome oxidase subunit (COX 1), internal transcribed spacer region (ITS), translation elongation factor-1 alpha (TEF-1α), large subunit (LSU), small subunit (SSU) and β-tubulin as well as two SCAR primers from RAPD profile were designed. The developed markers proved to be species-specific and validated against other fungal plant pathogens associated with pulses for cross-reactivity. The markers proved highly sensitive during conventional and qPCR analysis. Duplex PCR assays for R. solani and M. phaseolina; C. canescens and P. cruenta; A. alternata and A. tenuissima; and a quadruplex PCR assay for A. rabiei, S. sclerotiorum, S. rolfsii and F. oxysporum f. sp. ciceris were developed and validated for simultaneous detection of these pathogens in a single reaction. The assays developed in the present study were able to detect and identify major fungal plant pathogens causing disease in pulse crops.