Study On The Drought Resistance And Genetic Diversity Of Psathyrostachys Juncea Germplasm By ISSR Molecular Marker

The drought resistance of 14 germplasm of Psathyrostachys juncea at seedling stage was comprehensively identified and evaluated using the simulating drought stress and rewatering method in green house. The morphological and physiological indexes were measured and analyzed. The results showed that: along with the drought stress increasing, the relative water content and chlorophyll content in leaf were decreased; meanwhile, the relative electrical conductivity rate, content of MDA and free proline accumulation were increased. After rewatering, the values of measured indexes recovered at the different degrees. With cluster analysis, 14 P. juncea were divided into three grades according to the drought resistance, e.g. the stronger drought resistant germplasm were XMC01, XMC06, XMC10, XMC11; the medium XMC02, XMC04, XMC08, XMC09, XMC12, XMC13; and the weaker XMC3, XMC05, XMC07, XMC14.The genetic diversities of 15 Psathyrostachys juncea germplasm resources were analyzed by ISSR molecular Balker. For set up a optimized ISSR system we studied several factors include Taq DNA polymerase, random primers, Mg²⁺, and dNTPs which affect ISSR-PCR amplifying results of Psathyrostachys juncea. An optimized ISSR system was set up: the total volume was 25μl, including 2.5μl dNTPs, 2μl template DNA, 0.2μl Taq DNA polymerase, 1μl random primers, 1.5μl Mg²⁺, 2.5μl 10×PCR Buffer, 15.3μlddH₂O. The reaction process went as following: the temperature profile used for PCR was 94℃for 3 minutes, followed by 35 cycles of 94℃for 30 seconds, 46℃to 60℃for 35 seconds (different primer, different temperature), 72℃for lminute30 seconds, and was terminated with a 10-minute DNA extension step at 72℃.The eight primers selected for use and detected a total of 84 bands, among which 72 bands were polymorphic. The average percentage of polymorphic bands(PPB) was 85.7%, and the range of GS was from 0.4405 to 0.9048, which indicated a rich genetic diversity of P. juncea. Based on cluster analyses of the genetic characteristics, 15 P. juncea could be divided into 4 groups according to the nearest phylogenetic relationship. In most cases materials from the same region were in the same group thus showing a geographical distribution of genetic diversity of the tested materials.