Studies On Primary Infection Sources Of Curvularia Leaf Spot, Bionomics Of Pathogen And Evaluation Of Maize For Resistance To Curvularia Lunata

A new leaf disease of maize ,mainly caused by Curvularia lunata (Wakker) Boed is becoming prevalent in recent years in north China and the disease was found in Sichuan in 1999 firstly. Under Yaan ecological conditions ,the primary infection sources of Curvularia leaf spot and the bionomics of pathogen were studied .28 cultivators were evaluated for the resistance to the disease. The results are as follows:1. The mycilia and conidia of C.lunata in diseased leaves that suspended indoor and outside could overwinter successfully and that could induce occurance of the disease in field. The pathogen in diseased leaves in dry conditions could live at least 2 years. But the pathogen in fresh diseased leaves that placed on the surface or under the 3 centimetres of the soil could not overwinter safely.The conidia adhered to seeds could overwinter successfully and live at least 225 days. The pathogen in infected seeds could infect the seedling of maize but the infection belongs to masking infection,that is,apparent symptoms were not be observed in seedlings .C.lunata isolated from rice could infect maize and that isolated from maize could also infect the leaves and seeds of wheat.The results indicated that both diseased leaves and infected seeds were primary infection sourced of the disease under Yaan,Sichuan ecological conditions,and it still needs to be studied whether the C.lunata in other hosts (rice wheat etc) were the primary infection sources of the disease or not.2. C.lunata could grow at the temperature of 6-40and the optimum temperature was 28-32. It could grow at the PH of 4-12 and the optimum PH was 6-9. The optimum carbon and niteogen sources were soluble starch and nitrate respectively. The temperature for germination of conidia was8-40 and the optimum temperature was 25-35 . The conidia could germinate when the RH was above 90%. The sporulation on diseased leaves could be observed when the temperature was 8-38 and the RH was above 96.1%.The infection of maize by C.Iunata could be observed at 10-38 and at 30 the incubation period was the shortest and the disease progress was the rapidest.3. There was no immune cultivator and only one resistant cultivator among 28 evaluated cultivators. The types of spot could be used to identify the resistance of corn to Curvularia lunata.