Preliminary Studies On Cold-resistance Mechanism And Identification Of Ginkgo Germplasm

This paper studied the dynamic change regulation on morphology,chlorophyll fluorescence parameters,physiology and biochemistry of ginkgo leaf or branch under cold-hardening,overwinter low temperature or freezing temperature, discussed ginkgo cold-mechanism,comprehensively measured cold resistance of testing materials,and preliminarily.screened a group of ginkgo half-sib families and strains as relative higher cold-resistance abilities,in order to provide theoretical basis and cold-resistant germplasm for regional experiment,cold-resistant breeding and cold-resistant evaluation.The results were as follows:(1)The order of the semilethal low temperature of the half-sib families from low to high was 31^#,16^#,21^#,45^#,38^#,42^#,44^#,57^#,40^#,50^#,30^#,26^#,28^#,27^#,41^#,43^#, 32^#,9^#,54^#,29^#,35^#,18^#,36^#,34^#,19^#,56^#,39^#,53^#,11^#,10^#,15^#,55^#,33^#,17^#,37^#, 14^#,20^#,13^#,12^#;and that of the strains was 40^#,41^#,16^#,38^#,36^#,45^#,15^#,44^#, 19^#,53^#,17^#,50^#,56^#,57^#,35^#,32^#,55^#,42,43,10^#,18^#,14^#,37^#,12^#,9^#,34^#,28^#, 33^#,54^#,13^#,30^#,29^#,20^#,21^#,26^#,31^#,39^#,11^# and 27^#.(2)Cold hardening could improve cold resistance of ginkgo seedling,occurred a series of physiology and biochemistry changes to improve cold resistance,including water conditions improvement,metabolic pathway changes,antioxidant enzyme activities increasing,the ability of maintaining Ca²⁺low steady-state strengthening, energy metabolic strengthening and soon on,(3)The two ginkgo half-sib families as no cold acclimation were seriously hurt under -2℃freezing stress,which showed that leaf ultrastructure and photosynthetic system seriously hurting,root activity significantly decreasing,osmotic adjustment ability imbalancing,antioxidant activity lossing,hormonal regulation imbalancing. The above effects of freezing temperature on the ginkgo half-sib family as higher cold resistance were slighter and later.But cold resistance ability of ginkgo seedling after cold acclination strengthened,and the seedlings had better maintained the integrity of leaf ultrastructure and photosynthetic system,higher root activity,better the abilities of osmotic adjustment ability,antioxidant activity,and hormonal regulation.(4)During overwinter,ginkgo initiativly lowered it's shoot water content, increased bound water content and the ratio of bound water content to free water content;accumulated osmotic adjustment mechanism as soluble sugar and free proline;improved SOD,POD activity.Semilethal low temperature lowering and higher sprouting percentage of overwinter shoot after freezing stress treating were the synthetical reflection of cold resistance improvement. Dehydrating rate of ginkgo shoots,membrane permeability and membrane lipid peroxidation increased with tempeature lowering and treatment time lengthing under freezing temperature.SOD and POD activity,and soluble sugar and soluble protein content increased at firsr,then decreased,which showed that osmotic adjustment ability and antioxidant abilities were higher under relatively high low temperature and treatment early term,but those imbalanced under relatively low temperature and treatment late term.40^# strain had relative better abilities of water conservation, osmotic adjustment and antioxidant abilities,and imbalance of it's regulation ability of 40^# were later under relative low freezing temperature.(5)The order of cold resistance of 39 half-sib families from high to low was 21^#, 45^#,44^#,31^#,16^#,42^#,50^#,38^#,28^#,43^#,40^#,30^#,41^#,27^#,32^#,26^#,57^#,54^#,9^#,34^#, 11^#,39^#,18^#,29^#,53^#,15^#,19^#,35^#,56^#,12^#,55^#,36^#,10^#,13^#,20^#,17^#,37^#,33^# and 14^#.(6)The order of cold resistance of 39 ginkgo stone-used strains' shoots over winter was 16^#＞40^#＞41^#＞36^#＞45^#＞15^#＞38^#＞19^#＞53^#＞17^#＞44^#＞57^#＞43^#＞35^#＞55^#＞42^#＞10^#＞50^#＞56^#＞18^#＞32^#＞9^#＞37^#＞12^#＞30^#＞14^#＞26^#＞33^#＞34^#＞28^#＞13^#＞21^#＞54^#＞20^#＞11^#＞27^#＞31^#＞29^#＞39^#.The order of that under freezing stress was 16^#,38^#,17^#,40^#,41^#,36^#,45^#,15^#,53^#,44^#,19^#,42^#,57^#, 10^#,35^#,18^#,50^#,55^#,32^#,26^#,12^#,30^#,56^#,9^#,13^#,34^#,12^#,37^#,14^#,33^#,54^#,20^#, 28^#,11^#,31^#,27^#,29^# and 39^#.(7)The anticold and high-yield ginkgo strains included 45^#,10^#,19^#,38^#,44^#,43^#, 35^# and 55^#.