| This paper focuses on Bromus inermis which chosen from 12 regions at home and abroad to analyze theirs drought resistance and genetic diversity. The drought resistance research was divided into two stages:seed germination and seedling growth. Study on the drought-resistance used by PEG-6000 to simulated drought stress environments at seed germination stage and continuous drought at seedlings stage, and genetic diversity took random amplified polymorphic DNA (RAPD). The main results are as follows:(1) Seven indicators were selected to analyze drought resistance of seed germination, they were relatively germination rate, relative germination potential, relative germination index, relative vitality index, drought index, germination dynamic map and semi-lethal stress concentration. With the increased in concentration of PEG, the indices were downward trend. In these seven indicators, results of the relative germination rate, relative germination potential, drought index, germination dynamic map and semilethal stress concentration indicators almost were unanimous, reflecting that they were relatively better indicators for identification of the drought resistance at seed germination stage of B. inermis.(2)The relative water content of leaves, MDA content and cell membrane permeability were choosed as representative indicators at seedling stage. Result showed that leaf relative water content of each samples had different degrees of decrease with the extension of drought time, MDA content and relative electrical conductivity increase.(3) The semi-lethal stress concentration of samples from 12 regions were concluded to came to a cubic polynomial model:Y=b0+b1x+b2x2+b3x3, compared with two models commonly in the research of drought resistance of grass, that was linear equations:Y=b0+b1x; polynomial model (quadratic): Y=bo+b1x+b2x2, goodness of the cubic polynomial model was the best. This model was the anti-"S"-shaped curve, according to this equation to calculate the semi-lethal stress concentration, this result as opposed to germination dynamics, relative germination rate, relative germination potential and drought resistance index was fully consistent, this model could be in the application in the study of drought resistance of other forage.(4) The drought resistance at seed germination stage was comprehensively evaluated by using membership function method of fuzzy mathematics. As a result, these samples were divided into three levels, in which 1th,2nd,8th and 7th as stronger drought resistance ability rank, they respectively came from Jiangsu Province (JS), Poland (BL), Xinjiang (XJ3), and the former Soviet Union (QSL). The same method was used at seedling stage, the 2nd,9th (from Canada, JND),8th and 7th have stronger drought resistance ability. Integrated the two results, the 2nd,7th and 8th with strong drought resistance could serve as drought resistance varieties for further breeding.(5) Random amplified polymorphic DNA (RAPD) markers were applied to investigate the genetic diversity of twelve populations of B. inermis. The results showed that the percentage of polymorphic bands (PPB), Shannon's information index (I) and Nei's gene diversity index (H) were 87.36%,0.2933 and 0.1843 respectively, showing a higher level of genetic diversity. Genetic differentiations among populations (Gst) was 0.2735, it showed that genetic variation mainly exists within the populations (72.65%). And based on genetic differentiation, B. inermis can be identified as outcrossing species, and its high degree of genetic differentiation in outcrossing species. The cluster analysis showed that genetic distance was no significantly correlated with geographical distance. It maybe related to human's widely cultivation broadening the gene flows among populations. |
PDF Full Text Request