| Historically, rice blast caused by Magnaporthe grisea is well documented as the most destructive disease in rice. Therefore, the author had firstly carried out studies on population genetic structure of the blast pathogen in both mountainous and hilly ecosystems of rice blast disease, similarity of resistant gene analogue, RGA, of domestic cultivars, grain quality varieties and some rice germplasm resources, relationship of interaction between the blast pathogen and varieties, and utilization of mixture inter-planting of varieties in Hunan, China. These studies may result in understanding the genetic diversity of both rice varieties and blast pathogen, and relationship of intcraction betwccn them, and further some theoty basis and methods of both breeding of rice blast resistance and scicntific utilization of resistant varieties are expected to obtain. A total of 103 monoconidial isolates were collected froni 60 rice cultivars or lines, which are from both hilly and mountainous ecosystems in Htman. Each isolate was subjected to DNA fingerprinting analysis using Pot2 rep-PCR. At 62% similarity level, these isolates were grouped into 3 lineages. Seventy-two (72) isolates of mountainous areas were distributed in 3 lineages, while 3 lisolates of hilly area (except one isolate) were fallen into one lineage only. At 72% similarity level, overdll isolates co~tld be groLlped into 13 lineages. Of these lineage, L8, Lii and L12 were identified as the dominat lineage with l3梸23 haplotypes, which have frequencies of greater than I6~/~, while LI, L2, L3, L4, L5. L6, L9 and LlO were as minor lineages with I ? haplotypes, which have frequencies of less than 5%. It was also identified that 42.9% of isolates from the same host belongs to the same lineage and remaining belongs to two different lineages. These results showed as follows: (1) Population structure of blast pathogen in mountainous and hilly ecosystems of rice blast disease was genetically diverged. The genetic diversity in mountainous ecosystem was more complex than that in hilly ecosystem. Therefore, there was rather heterogeneous and potential variation in the pathogen population of the two ecosystems. (2) Genetic diversity of the blast pathogen population was obviously positively correlated with complexity of variety composition. in other word, more number of genetically diversified varieties would result in more genetic diversity of tIme blast pathogen population. Then author firstly advanced that due to great complexity of blast pathogen. mountainous ecosystem would be idea for one to set up the long-term identification nursery of rice 3 gerxnplasni resources and breeding materials against blast disease. This may have an important role in exploration and appraisal of both resistant germplasm resources and resistant cultivars, and breeding materials against blast disease. Two primer pairs, viz. XLRRfor/XLRRrev and S l/AS3, were used to fingerprint 24 rice varieties. Rich DNA polymorphism bands were observed for both primer pairs. However, XLRRfor/XLRRrev were found providing more amplified polymorphism bands than Sl/AS3 on RGA-PCR. Cluster analysis showed that 24 varieties could be attributed in 8? 10 groups at 80% similarity level. The results of this study also suggested that either XLRRfor/XLRRrev or combination of XLRRfor/XLRRrev and S l/AS3 using RGA-PCR were useful in evaluation of rice germplasmn in genetic response to rice blast. Cluster analysis was also performed for time same sets of cuit...
|
PDF Full Text Request