| Ilex verticillata is an ornamental tree species introduced in recent years in China,but the genetic relationship between the introduced varieties is unclear,which limits the breeding of I.verticillata.Meanwhile,few studies focus on drought resistance of I.verticillata,which limits the extension of this species to arid regions.In this study,genetic relationships between 12 I.verticillata varieties were first analyzed by ISSR markers,and two-year-old cutting seedlings of three representative varieties of I.verticillata were selected as materials to explore how I.verticillata respond to drought stress and if exogenous spermidine(SPD)could alleviate the adverse effects caused by drought stress.The results are as follows:1.Four primers with polymorphism among I.verticillata varieties were screened from 12 candidates ISSR primers and used for amplification of ISSR bands among the 12 I.verticillata varieties.A total of 63 bands were obtained,among which the polymorphic bands accounted for 90.48%.The genetic similarity coefficient of the 12 I.verticillata varieties varied from 0.54 to 0.87.The results of clustering showed that there were different degrees of phylogenetic relationship among the 12 I.verticillata varieties.2.With the degree of drought stress increased,the leaves of the three varieties of I.verticillata gradually appeared chlorosis,the edge of the leaves got dry;the relative water content(RWC),specific leaf weight(SLW),chlorophyll content,leaf nitrogen content,net photosynthetic rate(Pn),stomatal conductance(Gs)and electron transport rate(ETR)reduced significantly;malondialdehyde(MDA)content,activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased first and then decreased;the contents of soluble sugar and abscisic acid(ABA)rized continuously,but the levels of auxin(IAA)and gibberellin(GA)showed the trend of continuous decline.3.Compared with single drought stress treatment,when exogenous SPD were pre-added simultaneously,RWC and SLW of the leaves were significantly increased;the chlorophyll content,leaf nitrogen content,Pn,Gs,ETR were significantly increased;MDA content and activities of SOD in I.verticillata leaves decreased significantly,while activities of POD and CAT increased significantly;soluble sugar and ABA content decreased significantly,but IAA and GA content increased significantly in the leaves of I.verticillata.4.By comparing the leaf phenotypes and physiological indexes of the three I.verticillata varieties under drought stress conditions,it was found that the drought resistance of the three I.verticillata varieties was different,among which I.verticillata(L.)A.Gray had a relatively higher drought resistance. |
