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Validation of molecular diagnostic methods for specific detection of Magnaporthe oryzae Triticum pathotype, the causal agent of wheat blast


<div><span>Wheat blast, caused by the fungal pathogen <em>Magnaporthe oryzae Triticum</em> pathotype (MoT), first emerged as a serious threat to wheat production areas of Brazil and subsequently spread to Argentina, Bolivia, and Paraguay. More recently, wheat blast has emerged in Bangladesh. With yield losses that can reach nearly 100% under optimal environmental conditions, there is growing concern that MoT will continue to spread to other wheat-growing regions of the world. Until recently, the diagnosis of wheat blast relied on morphological identification of <em>M. oryzae</em> spores or PCR-based assays, both of which are limited to confirmation at the species level and cannot distinguish pathotype. There are currently no approved regulatory methods for detection of MoT in the USA, and the International Plant Protection Convention (IPPC) has listed MoT as a pest where there is an immediate need for internationally harmonized diagnostic protocols. In a recent publication, whole-genome sequences of multiple <em>M. oryzae</em> strains were used to develop PCR-based assays to differentiate MoT strains from other <em>M. oryzae</em> pathotypes. The resulting PCR assays have been optimized, evaluated, and subjected to a robust validation process by the CPHST Beltsville Laboratory. Validation of the assays yielded one PCR assay for use with screening wheat samples to detect <em>M. oryzae</em>, and two additional PCR assays that specifically detect MoT. Data from the validation testing process will be presented.</span></div>