Studies On Disease Resistance And RAPD Analysis Of Yam Germplasm

This paper includes three parts, the first part is the identification of resistance to the yam diseases, the second part is the research on resistance mechanism, the third part is the genetic diversity analysis.38 yam varieties were identified and the results showed that the Luan chuan wild yam was immune to the the leaf spot(Cylindrosporium dioscoreae Miyabe et Ito), the wild yam varieties from Yanshi and Songxian and a few of cultivars such as Tiegun yam, Japanese round yam demonstrated high- resistance level, some cultivars such as Wenke yam No. 2 demonstrated moderate high-resistance to the anthracnose(Gloeosporium pestis Massee). Most of the cultivars such as Taigu yam are susceptible to the diseases in Huai yam-growing area.Through the reseach of the resistance mechanism, it was found that there was significant positive correlation between the density of leaf pore, the waxiness content, the phonel content and the resistance to the yam diseases. The correlative coefficient was 0.90024 between the phonel content and the resistance level. In this reseach, the significant positive correlation between the density of leaf pore and the resistance demonstrated that it can enforce resistance in the infection when there is high density of lesf pore in the yam germplasms. The waxiness is also important for resistance because of its physical character; the phonel can directly poison or inhabit the pathogens in the plant body so that it is important in the resistance. As the pivotal enzymes in the plant resistance, PO and PAL occurred obvious change between the injected leaf and non-injected leaf, but some raise, other reduce.there was not obvious correlation in this reseach. So the process mode is morecomplicated and more reseach are required about the rule of PO and PAL in the plant resistance.The genetic diversity of 15 yam variaties were analysed using random amplified polymorphic DNA(RAPD), 11 random primers were selected from 100 ones. A total of 95 DNA bands were amplified, all(100%) were polymorphic. The number of DNA band amplified by each primer was 8.64. The MW of the amplified bands were between the 0.2-2kb. 15 yam can be classified into 3 groups by cluster analysis. The results showed that the Huai yam obtain the uniq genetic characrer and some variaties were not classified into one group because of different zone origin. These yam germplasms exhibited extensive genetic variability, there were plent of utilize space in breed-cultivated process.