Abstract: Abstract: Head smut of maize substantially reduces grain yield. Two varieties of maize were used in our experiments: huangzao4 which is susceptible to maize head smut and Mo17 which has resistance. The DNA of the leaves, root, stem and male ear from Sporisorium reiliana of the infected and noninfected young and mature maize plants is detected with the existence of specific DNA only appearing in the pathogen S. reiliana’s genome by PCR based assays. Through the PCR amplification, we can distinguish the young plant which has been invaded by the S. reiliana from the healthy plant at the early invaded Stage. So it provides a sensitive and reliable tool to make an objective appraisal of the S. reiliana’s infection. The study of the course of the S. reiliana’s spread in the maize indicates that the resistance of the maize to the head smut majority represents in the stage of infection and spread. And the result shows that it couldn't present evidently resistance during the growth of the male ears. Key words: Maize (Zea mays L.); Head smut; PCR; infection; spread

Key words: Maize (Zea mays L.), Head smut, PCR, infection spread