Analyses of maize embryo invasion by Sugarcane mosaic virus

Maize seeds from a susceptible inbred line Mo17 to Sugarcane mosaic virus (SCMV) were investigated for seed transmission of the virus. Seed grow-out tests indicated that the average infection incidence of SCMV in seedling was 4.81%. Four combinations of crosses between healthy and/or infected parent plants were performed, the results indicated that SCMV could be transported to progeny seeds not only by infected female plants, but also by pollen of infected plants through fertilization. However, the main pathway for virus entering to seeds and embryos was from maternal plants. Viruses could invade immature embryos before 15th day of post-pollination or earlier in inbred line Mo17, and maintaining infective in maize embryonic during seed development, dehydration and seed germination. Electron microscopy investigation of anthers from the infected-plants revealed that abundant virions and pinwheel inclusion bodies occurred in the endothecium and middle-layer of anther walls, and no virion was found in the tapetum and the independent pollen grains. ELISA, infectivity test of anther and pollen also indicated that the infective virus from infected plant anther was associated with the surface of pollen grains. The virions were also located in the cytoplasm of infected-ovary wall and in the vascular bundles near to ovular pore by means of ultrastructural, immunohistochemistry and in situ hybridization histochemistry. However, no virion was found in the nucellus and megaspore.