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Understanding Maize chlorotic mottle virus transmission through seed: localization and infectivity

Pauline Bernardo: Ohio State University

<div><em>Maize chlorotic mottle virus </em>(MCMV) is the primary driver of Maize Lethal Necrosis, which has emerged recently in East Africa, Asia, and South America and has significant impact on maize production and food security. MCMV introduction to non-endemic areas is thought to occur through seed. To develop a better understanding of the mechanisms underlying MCMV transmission through seed, we investigated its distribution and infectivity in infested seeds from Kenya and Hawaii. MCMV was detected at high levels in the pericarp and pedicel in hand-dissected seeds using ELISA. Significantly lower levels of virus were detected in the endosperm and embryo, and no virus was detected in embryos that were washed after dissection. Subsequent immunofluorescence microscopy of seed sections indicated MCMV was localized to the pericarp and pedicel. Because no transmission of MCMV from infested seeds was detected in 1,800 seedlings, we tested the infectivity of virus isolated from these seeds. Although intact MCMV virions could be detected using transmission electron microscopy, and virus titer was sufficient for transmission of viable MCMV isolated from leaves, no transmission of MCMV from seed to uninfected maize could be achieved using leaf rub or vascular puncture inoculation. Our results indicate that MCMV from seed has low infectivity and is limited to maternal tissues, suggesting that seed treatments may reduce virus transmission through seed.</div>

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