Studies On Identification And Screening Of Resistance To Sclerotinia Trifoliorum In Medicago Sativa L.

Alfalfa is important livestock forage because of rich nutritional value and considerable yield. With the expansion of cultivation areas in recent years, alfalfa disease has become increasingly serious, especially in Southern Region of China, the temperate and humidity climate provide living conditions for sclerotinia trifoliorum. sclerotinia rot has become one of the main factors restricting the yield of alfalfa in these areas. The disease occurs throughout the growing period of alfalfa and seedling is particularly devastating. Identification and evaluation of resistance to sclerotinia trifoliorum is the base for cultivating and applying resistant varieties to prevent sclerotinia rot. At present, the identification of resistance to sclerotinia trifoliorum only reported by Yuan Q-H whose methods were limited on natural infection of field, therefore, searching for fast, reliable and simple methods is great urgency. This study attempts to provide reference for identification such as soaking root, screening resistant mutants and excised leaf tissue inoculation in alfalfa. The results were proved as following:1. Sclerotinia trifoliorum culture filtrate was of temperature-resistant, pressure-resistant, dilution-resistant, durability, et al. The toxicity of culture filtrate originated from different sclerotinia trifoliorum was different, and originated from the same sclerotinia trifoliorum was also different to alfalfa varieties. 1～1/4 dilution was the optimal concentration for procedure of soaking root for seedlings, but these seedlings were hardly survival after treatment. The PD culture filtrate has also slight pathogenicity which can be eliminated by dilution.2. Sclerotinia trifoliorum culture filtrate was good selection medicament for resistant mutants and the optimal concentration was 1/10～1/5 dilution. It was better for callus to treat with diameter of 4～6mm and 96h.3. the same alfalfa collections were tested between spring and autumn when sclerotinia rot occur seriously, the results were concordant in two seasons, but the disease index was higher in autumn than spring. There was no plant of more than 250 collections tested represents highly resistant to sclerotinia trifoliorum, only a small amount of plants shows moderate resistance. All shows that collections which highly resistant to sclerotinia trifoliorum were very few in nature and the work of screening procedure was hard.