Studies On Biological Charac-Teristics Of C.Lunata And Resistance Of Corn Resources

Corn C.lunata leaf spot caused by C.Lunata is important disease. In recent years, the epidemic area of this disease in main maize production zone is expanding annually and the state of it is becoming severer and severer. At present it has evolved from a secondary disease to the primary one. In this report we studied the biological characteristics, factors of infection, and as well as the resistance difference between cultivars or inbred lines with different sources. We drew conclusions as follows:We made certain of the optimum condition for the germination of the conidia of Curvularia and the optimum condition for the growth of mycelia. The germination temperature is from 28 to 35 , 32 is the optimum temperature. Only when the RH is over 96% can it germinate. The range of pH for germination is from 4 to 11,The optimum pH is from 5 to 8. The growth temperature of mycelia is from 25癈 to 35癈. The optimum temperature for the growth of mycelia is 30 . When pH is from 3 to 10 the mycelia can grow, while the optimum pH is from 4 to 8.Under the condition of surface soil in winter and when the soil is arid the pathogen can survive winter safely in the residue of plants which became the first source of infection in the next year. The virulence of strains is different. Where there are strains with strongly virulence the disease will be severer. The leaves (substance on the leaves) of different growth stage have apparently different extent of effect on the germination of the spores of C.lunata. The facilitation effect of the leaves (substance on the leaves) of silking stage is especially strong. Temperature and humidity are two important factors which affect the infection efficiency and incubation stage of the disease.There is apparent resistance difference between varieties and inbred lines. The latter is clearly weaker than the former. The resistance of hybrids and inbred lines with different source are quite different. Some germ plasm which have been used for many years such as Ji63, Huangzao4, Dan9046, Dan9041, Tie7922, Ye478, Shen5003, Mol7, Dan340 and E28 and so on are sensitive to the disease(MS-HS), while some germ plasm of new-bred populations and some exotic germ plasm with tropical and subtropical blood such as 78599 are all resistant to the disease (R-HR). There are closely relationship between hybrids and their parents on disease resistance. We required a series of varieties and inbred lines with resistance to C.lunata Boed. in order to provide germ plasm resources for maize breeding. The disease resistance will gradually weaken with the growth of plants. Therefore the plants appear high resistant at seedling while become sensitive at silking stage.The study laid foundation for the resistance breeding of Corn C.lunata leaf spot and provided germ plasm resources.