Drought Stress And Genetic Diversity Of Seedlings Of Medicago Falcalta

In this paper, basing on the morphological characteristics, physiological ecology andmolecular biology, different genotype Medicalgo falcalta which are perennial leguminousplants were studied on the morphological traits, the strategies of different genotype seedlingsunder drought stress and the genetic diversity. The results showed that:⑴ Medicalgo falcalta had relative small leaf area. Its stem was decumbent and formedlotiform conformation. Its seedlings grew very slow, but had strong roots and a lot of rootnodules. Its accumulation of biomass and speed of growth were lower than that of Medicagovaria. Integrative considering the morphological characters, growing speed and accumulationof biomass, Cv.Culuskaya, L.Yakuskayayellow, and XiMeng showed more elegant qualitythan others, and deserved further study.⑵ In the experiment of drought stress on Medicago falcalta seedlings, the held thestress intensity by weight and drought-rewater. The drought stress carried out on the fourweek-old seedlings. The result was that, the net photosynthesis rate, transpiration rate, stomaconductance and instantaneous water use efficiency of all the seedlings decreased. Butdrought stress did not affect the photo saturation of Cv.Daviluya, Cv.Culuskaya, which was600μmol/m2s. By contraries, the photo saturation of GongNongⅠand XiMeng decreased 2/3and 1/3 respectively. The effect of drought on the morphological characters of Medicagofalcalta seedlings showed the same trend, which was that height, root length, ramification,root collar diameter and leaf area were decreased, but relative leaf area increased. Understress, the root length/height increased, furthermore the increases of Cv.Daviluya andCv.Culuskaya were significant. Drought stress did not only make the decrease of biomassaccumulation, but also affected the distribution of product of assimilation. Root/shoot ofCv.Daviluya, Cv.Culuskaya and XiMeng under moderate stress was higher than the black, butlower than that under severe stress. The root/shoot of GongNongⅠdecreased as the stressbecoming severer, but it was not significant. The stem/leaf increased though under stress. Inthe circumstance of this study, Cv.Daviluya and Cv.Culuskaya could grow relatively wellunder moderate stress, and could complete normal physiological functions. Therefore, theyhad stronger drought resistance than other genotypes. In the opposite, GongNongⅠ wassensitive to drought stress, and was injured very badly even in the moderate stress. In thedrought-rewatered experiment, Cv.Daviluya, Cv.Culuskaya and XiMeng, three material ofMedicago falcalta, showed corresponding strategies changes in morphology and biomassaccumulation to drought stress. They had significant compensatory growth in the re-wateredperiod. So these three genotypes had elegant drought resistance.⑶ Random amplified polymorphic DNA (RAPD) analysis demonstrated that 33 randomprimers produced 353 loci, obtaining 263 polymorphic loci in 10 different genotypes ofMedicago. The percentage of polymorphic loci was 74.5%, and each primer produced 5-17belts. Genetic similarity changeed from 0.488 to 0.686, average 0.592. Through clusteringanalysis, we divided the 10 materials in to three groups: CaoYuanⅠ, CaoYuanⅢ, Alfakingand Cv.Daviluya were the first group, L.Yakuskayayellow, HuMeng, MengGu and XiMengwere the second group, and Cv.Culuskaya was the third group.