Identification Of New Chicory Variety With Drought-resistance And High-yeild By Space Mutation Breeding And Study On Drought-resistance Mechanism

Cichorium Intybus L.is an fine introduced variety with high yield and good palatability.Till now,it was extensive popularization in Guizhou and Sichuan Province,applying for mixed grassland feeding pigs,rabbits,cattles and sheeps.However,under the drought circumstance,the introduced variety not only grow slowly,but also bolt easily after mowed,thus minimiseing the yield.According to the successive drought weather in autumn and winter,the research choose a new variety with high yield and strong drought resistance.By studying on the drought resistance mechanism,we can provid a theoretic basis for the choosing of an new drought resistance variety.Taking the new strains of chicory mutated in space in2006and the primary varieties (Puna and General) for instance,the RAPD marker,high yield and drought resistance choosen,and drought resistance mechanism have been studied.The conclusions are showed:The genetic relationship and production performance of29Cichorium intybu were studied in this research by using RAPD method. The result showed that15primers selected from100random primers were characteristic of high polymorphism, repeatability and stability.78DNA fragments were amplified, including63polymorphic bands. The average percentage of polymorphic bands was87.77%, cluster analysis showed that genetic similarity coefficient of C. intybus was ranging from0.69to0.80, there was a lower genetic diversity among germplasm resources of C. intybus tested. PA-186clustered alone. The fmgdings indicated an incomplete correlation among the dendrogram and phenotypic characteristics. According to production performance, the yield of twelve new lines were higher than Puna chicory and Jiangjun chicory.We studied the anatomical structures related to drought resistance of the leaves of15new chicory strains by space mutagenesis based on9xeromorphic indexes, did the single factor multiple comparison between two strains in order to conclude the sensitiveness sequence of the9indexes to the drought, and the clustering analysis based on4most sensitive indexes including the stoma density of lower epidermis, the stoma length, the thickness of bundle, the thickness of leaves. The results showed that there was highly significant difference between the strains. The following was the sequence of the sensitivity:lower epidermis stoma density>lower epidermis stoma length> upper epidermis stoma length>upper epidermis stoma density>bundle thickness> leaf thickness, midrib thickness> upper and lower epidermis thickness. And according to clustering analysis, the15strains could be divided into three classes in terms of the ability of the leaves structures against the drought:PA-95, PA-96, PA-11, PA-93, PA-49, PA-20, PA-82, PA-42were best while PA-43were worst, and PA-36, PA-31, CK, PA-186, PA-54and PA-26were between them. The leaves of the different new strains had the different anatomical structures related to drought resistance.Under drought stress, the three Cichorium intybu’s Water Metabolism and osmotic substances have changed,as showed that:the drought stress result in relative water content’descent and the water saturation deficit increase.The more stronger the drought resistance is,the more slowly the water saturation deficit increase with the low range,and the more slowly the relative water content descent with small amplitude.While The more weaker the drought resistance is,the more fast the water saturation deficit increase with the high range,and the more rapid the relative water content descent with big amplitude.PA--82with strong drought resistance has big amplitude in soluble sugar content, CK with midle drought resistance ranks modest,and PA--43with weak drought resistance ranks the lastUnder the drought circumstance, the soluble Protein of PA--43increased first,and decreased then,owning a weak regulation. Both PA-82and CK has more stronger endurance and adaption than PA-43.The three strains’s proline content enhanced first,then reduced. The range of increase in PA--82with stronger drought resistance is bigger than PA--43with weaker drought resistance.The study on the active oxygen scavenging system of three strains concluded that:due to the drought resistance, enzyme activity of leaf reduced after enhanced first,getting the summit at9.03%soil water content. Enzyme activity of both CAT and POD that are important regulation ingredients keeps a high level at6.72%soil water contentCompanying with drought stress increase,the malondialdehyde inclined to ascend. The PA-43with weak drought resistance has a big range of MDA enhancement,thus the harm for plant added successively. While the PA-82with strong drought resistance has a small range of MDA enhancement,keeping the stable level. The carotenoid content inclined to add,but the time of PA--43carotenoid increase lag behind the other two strains,the total ascending range is:PA-82>PA-43>CK.The photosynthetic properties and photosynthetic responses to drought stress in the pot experiment of three chicory (Cichorium intybus L.) strains with different drought resistance, space-mutagenesis-bred strains PA-82and PA-43and their initial strain CK, were studied using Li-6400portable photosynthesis system. The results showed that diurnal time courses of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Cond) presented as double-peak curves. There was an obvious midday Pn depression, which was caused by nonstomatal factors. Highest Pn, Tr and Cond values were observed in PA-82, and lowest corresponding values in PA-43(P<0.05). Intercellular CO2concentration (Ci) of three strains showed an opposite course to that of Pn, which reached its valley at10:00-12:00. PA-82had the highest water use efficiency (WUE), followed by CK, then PA-43. Pn, Tr, Cond, maximal photochemical efficiency of PS II in dark adaptation (Fv/Fm), potential photochemical efficiency (Fv/FO), and coefficient of photochemical quenching (qP) decreased with the aggravation of water deficit. Among the three strains, the parameters of PA-43dropped to a greater extent at a highest speed, followed by CK, then PA-82. With the aggravation of water deficit, Ci and co-efficient of nonphotochemical quenching (qN) increased to a greater extent at a highest speed in PA-43. Our results suggest that PA-82and CK have higher resistance against severe water deficit in comparison with PA-43.The result that endogenous hormones altered under the water stress concluded that ABA content inclined to increase when confronted drought stress. The ABA content of PA-82with strong drought resistance and CK with middling drought resistance didn’t change under the light water stress,while ascended largely under the modest and severe drought stress.The ABA content of PA--43with weak drought had an equipotent increase under each water stress disposal.Under the severe drought stree,the variety with strong drought resistance owned stronger drought stress than that with weak drought resistanc.The IAA content of three strains ascended,companying with the increase in stress,the IAA content of PA-82enhanced largely, and then the IAA content of CK and PA-43increased a little.The regulation capacity of PA-82is stronger than that of CK and PA-43.Under the water stress circumstance, all of the stains’GA3content decreased, demonstrating that by slowing down the growth speed,plant can alleviate the pressure upon the normal biophysical activity resulted from the water defect.The GA3decrease range of PA-82and CK were bigger than that of PA-43.Four morphology and7physiological indexes were chosen for evaluating drought resistence of chicory.