Study On Ustilago Maydis Biology And Resistant Identification Of Maize (Zea Mays L.)

Ustilago maydis is a serious disease in maize production in the world, the general incidence is 5% to 10%, it cause yield loss about 30% to 80%. The basidiospore and secondary spore of Ustilago maydis have a strong tolalance to challenge environment. They can live for a long time in dry soil surface and inside. In the recent years, chlamydospores are accumulated year by year in soil due to the extension and continious cropping of compatible varieties, as well as the changes of climate factors, which results in the epidemic of Ustilago maydis in a faster spread, as an main disease in maize production areas of Huang-huai, northeastern and northwestern. Because of the long period of frist penetration against that short phase of agentia residual effect, chemical control is inefficient. In constrat, breading and extending resistance varieties are the most efficient way. By study on Ustilago maydis biology and resistant identification of maize, this study aimed at providing theoretical basis for resistant breeding of Ustilago maydis and germplasm improvenment.The trial studied Ustilago maydis biology, resistance identity of maize and chemical control techniques by the culture conditions of Ustilago maydis, the cytology observation, antibacterial test, in field conditions by diferent inoculation methods and concentration were compared. The results as followings:1. Through the comparative study of biological characteristics of Ustilago maydis, results showed teliospore germination best when the pH was 5.0 and the optimal temperature was 27℃, the mixed liquor of formaldehyde and potassium permanganate could promote germination of teliospore, hydrogen peroxide and sodium hydroxide had inhibition effect on it. The germination rate of teliospore was added up to 86.2 % on improved PDA medium. Ustilago maydis could grow well at the condition of 25-30℃, pH7.0, it was able to make use of various carbon and nitrogen source, the best source were sucrose and potassium nitrate. The optimum conditions for Ustilago maydis grow and sporulation was PDA medium. The Ustilago maydis was yellow-white small point and leather-like in earlier period, the colony became dark brown, ropiness surface and not smooth in latter period. Basidiospore were colorless, spindle-shaped, septate and branch, most four septates.2. Inhibition of hyphal growth of Ustilago maydis by four fungicides was assayed on PDA medium. Carbendazol had the highest inhibitory effect of hyphal growth under the each concentration, it could inhibit basidiospore production and germination rate of basidiospore obviously. So the efficiency of carbendazol in the lab was the best among the four fungicides. The effect of topsin-methyl was good, too. So they could be used to control Ustilago maydis in practice.3. The resistance identity of maize for Ustilago maydis indicated that the most effective inoculating method was to inject the teliospore into the corn plant, which caused the highest incidence rate of Ustilago maydis. The optimal time of inoculation was 6 leaf-stage, in this period, the disease occurred very sufficiently. The optimal concentration for injection was 9-10×103telispore/mL.4. The agronomic character of maize inoculated with Ustilago maydis and controls were investigated. The results showed Ustilago maydis had great effect on plant type traits and ear traits, and had the biggest effect on utility spike and yield of single strain.