Establishment Of Rice Blast Nursery And Evaluation On Screening And Breeding For Blast Resistance In Rice (Oryza Sativa L.)

Rice blast caused by Magnaporthe grisea is as one of the most destructive diseases in rice for its world-wide distribution. Blast resistance breeding and growing resistant cultivars are the most efficient measure to control the disease. Therefore, this work has firstly put into combining both blast nursery and resistant breeding, and carried out studies on population genetic structure of the blast pathogen similarity, identification of rice cultivars and lines resistant to blast and both screening and evaluation of resistant breeding to the disease, as well as systematic analysis of the similarities of the 21 varieties with resistance gene analogue, RGA.15 villages of 10 towns in Liuyang city, Taojiang county, Changsha county, Hunan Province, during booting to ripeness of late rice in 2001, were surveyed on the occurrence and local damage history of panicle blast, disease ecology, meteorological factors, geographical isolation, irrigation, communication, ect.. Liuyang Daweishan Rice Blast Nursery, based on integrated analyses about the above factors was selected, which locates at Daweishan National Forest Park, Rongwan village, Daweishan town, Liuyang city, viz. 11405rE, 28?0TSf, 400m with elevation, and belongs to the seasonal wetness climate with central Asia tropics, where it has annual average temperature with 17.3癈, with average 5.2癈 and 28.9癈 in January and July respectively, annual average rainfall with 1552mm, yearly average sunlight with 1656h and frost-free duration with 262d. Based on observation during rice growing, time of keeping free water on rice leaves was more than 15h. And 7350 rice entries tested in the blast nursery in 2002 and 2003 have proved that it has strongly differential ability, sustainable ecological environment and a good natural isolation condition as the nursery or breeding base.A total of 129 mono-conidial isolates was collected from Liuyang, Anhua and Taojiang in Hunan. Each isolate was subjected to DNA fingerprinting analysis using Pot2 rep-PCR, and 24 band types were obtained. At 72% similarity level, these isolates were grouped into 4 lineages. Isolates of mountainous areas, Liuyang, Anhua and Taojiang were distributed in 4 lineages. Of these lineages, LI, and L3 were identified as the major lineage, which have frequencies of 41.09% and 46.51% respectively. Based on homology or difference of bandtypes, 129 isolates can be separated into 24 haplotypes, among which H5, H6 and H17 are dominant ones and they have frequencies of 16.28%, 16.28%and 17.83%, respectively. Therefore, there was rather heterogeneous and potential variation in the pathogen population, based on constitute of lineages and haplotypes.According to genetic diversity constitute of the blast pathogen population, 6 isolates, respectively subjected to HI, H3, H5, H7 and H23, which had not been tested in DNA fingerprinting analysis using Pot2 rep-PCR in the nursery in 2001, were inoculated on 4 spread susceptible varieties, Xiangaizao 7, Xiangwanxian 11, Huawanyou 1 and Peiliangyou 288 in nursery test in 2002. 7 Chinese differential varieties and a set of near-isolgenic lines (NILs) of ERRI were used as virulence monitoring of races in the nursery. 10 varieties except for Tetep appeared from moderate susceptibleness to high susceptibleness. And a few of typical susceptible lesions on Tetep could be also found in nursery test. The result showed that there were 7 race groups in the nursery. Therefore, the blast pathogen population in the nursery contains rich genetic diversity based on virulence monitoring of nursery races.7350 entries, including varieties and lines, in the nursery were tested in 2002 and 2003. The results indicated that there were 491 from high resistance (HR) to moderate resistance (MR) and 2892 from high susceptibleness (HS) to moderate susceptibleness (MS) for leaf blast, which had HR-MR frequency of 14.52% and HS-MS one of 85.48% in total 3383 entries in 2002, while 769 entries with HR-MR and 2084 entries with HS-MS for panicle blast, which had HR-MR frequency of 26.94% and HS-MS o...