Histology And Ultrastructure Of Resistant Mechanism Of Brachypodium Distachyon To Puccinia-Striiformis, And Research Of The Nucleus Distribution And The Infection Way Of Puccinia-Striiformis

Brachypodium distachyon, which has the main characteristics of the model plant such as simple nuclear genome, high capacity for plant regeneration, inbreeding annual with a life cycle, can be used as an important model plant for study in temperate cereals. It has been demonstrated that the reasonable use of resistant model pant cultivars is the most effective and economical method to control wheat rust diseases. Nonhost resistance, shown by an entire plant species to a specific parasite or pathogen, is the most common and durable form of plant resistance to disease-causing organisms. Therefore it will have broad application prospects in Agriculture. In this paper, the penetrating process between specific race of Puccinia striiformis and a new model plant Brachypodium distachyon was examined by means of fluorescent microscopy, differential interference contrast microscopy and electron microscopy.Study on the interaction between model plant and rust can reveal the resistant mechanism of the host plant and the pathogenic mechanism of the lust fungi, which provide further information for selection and reasonable use of resistant cereal cultivars,and also lay an essential foundation for exploring the host resistant mechanism from biochemical and molecular biological aspects.The results were obtained as follows:(1) Puccinia striiformis could infect Brachypodium distachyon, the infection process is similar to that of the wheat, but it included obvious inhibition of hyphal growth and decrease of formation of haustorial mother cells and haustoria. It can produce the hyphal colony. There was occurrence of nonhost cell necrosis at infection sites, and Brachypodium distachyon can produce visible symptoms.(2) Series of abnormal changes occurred in intercellular hyphae, haustorial mother cells and haustoria during pathogen development in the Brachypodium distachyon. At the same time, the structural defense reactions such as formation of cell wall apposition, papilla and necrosis of host cell were essentially expressed in the infected leaves of the Brachypodium distachyon, which constitute essential factors of resistance. (3)The kind of the interaction between Puccinia striiformis and Brachypodium distachyon belongs to the second one,which is known as the nonhost cell necrosis. As compared to susceptible wheat cultivar, the observation of Brachypodium distachyon following infection by the pathogen revealed a striking resistant characteristic in histology and ultrastructure.(4)The nucleus distribution for the different living stage of Puccinia striiformis are as follows: most of the urediospore have 2 nucleus, just like that of the germ tube .We can see that rare urediospore has 3 or 5 nucleus, and the germ tube have 1 to 4 nucleus, but most of the germ tube have 2 nucleus.(5)The observation discovered that there are two ways for Puccinia striiformis infecting wheat: direct infection and appressorium formation. A large amount of the Puccinia striiformis follow the direct infection way.(6) One of the influence factors of the infection way of Puccinia striiformis is temperature. Under the temperature of 4℃, the amount of formation of appressorium is a little higher than the temperature of 16℃. However, a large amount of the Puccinia striiformis follows the direct infection way under the two different temperature conditions.