Rapid Detection Of Pathogen Of Maize Crazy Top And The Disease Control

Crazy top, caused by Sclerophthora macrospora, is a destructive disease on maize. Based on the development of the research on crazy top undertaken by ICS-CAAS during 1996-2003, some experiments including stain methods for detecting mycelia and oospora, molecular detection techniques to pathogen, conditions of oospore germination, the disease induced and control. The main results are as follows:1. Four stain methods, zinc-chlor-iodide, cotton blue lactophenol, cotton blue and MTT, were evaluated in its efficiency on detection of pathogen mycelia and oospora specifically. Every stain method can detect oospora clearly in maize tissues, but only method of stain with zinc-chlor-iodide can detect the oospores, antheridia and antler-shape mycelia, which was special for S. macrospora, with orange or purple color in maize tissues.2. Using the primes, ITS1/ITS4 and DC6/ITS4, a 900bp band was amplified, cloned and sequenced. The sequence data showed that it was one of oomycetes because it was very closely with the sequences of Phytophothora sojae and Plasmopara viticola..More researches should be done for confirming the sequence as one part of DNA of S. macrospora and for designing the specific primers to detect the pathogen. At first build a method of extraction minim DNA. then it got the PCR product by primer then the dribs was reclaimed, , then got it sequence. The sequence have high comparability with.3. The disease was induced by soil collected from diseased field, debris of infected plants, seeds grown in infected ears in glasshouse condition. No excited results were obtained. In 2005 it was successful to induce the disease by submerging maize some times on germination and seedling stages in 24 hours in Zhongning, Ninxia. In this experiment the susceptible variety, Yedan 13, was infected with the high infection percentage, 45.6%. There was good result on control experiment by dressing seeds with metalaxy and mancozeb.Because of the difficulty on research the S. macrospora, which is not to be cultured in media, there are lots of work should be done to understand the pathogen characters and disease development. This study just give some results and information to future researchs.