Analysis On Drought And Cold Resistance Of Main Parent Xiaoyan22and Its Genetic Contribution To Derived Lines

New wheat cultivar Xiaoyan22was bred through distant hybridization techniquecombining conventional breeding by Northwest A&F University, which was approved byShaanxi Province variety approve committee in1998and national variety approve committeein2003, what’s more, it was taken as control variety for Shanxi Province since2001and it isthe first main wheat cultivar because of its large growing area that has been lasting more than10years. The reason for Xiaoyan22being such an excellent cultivar is that its strongadaptability to drought and cold resistance as well as its high yield and quality. Therefore, ithas a theoretical and practical significance for wheat breeding to investigate its reaction tostress (drought and cold). Besides, based on main parent Xiaoyan22, Xinong9871and other6cultivars as well as several new lines which were in trial have been bred, so furtherunderstanding the genetic contribution of Xiaoyan22to its derived cultivars would help tomake better use of main parent.In2012-2013, three experiments were carried out to study the effect of long-termdrought stress, low temperature stress on physiological parameters and grain yields in winterwheat (Triticum aestivum L.), combined with SSR molecular marker, which aimed atevaluating the drought resistance, cold resistance of core parent Xiaoyan22and its geneticcontribution to its derived cultivars, at the anti canopy in the Dongyuan plots, the originalNorthwest Institute of Botany, Chinese Academy of Science and overhead light plant growthchamber in the Institute of Soil and Water Conservation, Northwest A&F University. Theexperiment had3parts, namely drought stress, cold stress and analysis on genetic diversity.In part1, Xinong979and other6cultivars were taken as tested materials, plants weresubjected to three levels of drought stress: CK(control, well-watered), MS(moderate drought),SS(severe drought) from the beginning of jointing stage, then the relative electric conductivityand some indexes were measured during booting stage, flowering stage and grain-filling stage.In part2, Xiaoyan22and other4cultivars were taken as tested materials and they weresubjected to cold temperature at the jointing stage(1℃±1℃;0H,24H,48H,72H) and bootingstage(2℃±1℃;0H,24H,48H) separately, then the cold-related indexes were measured. Inpart3, SSR molecular marker was used to understand the genetic contribution of Xiaoyan22 and its derived cultivars.The effect of drought stress on physiological parameters and yield of winter wheat:(1) Under moderate drought stress and the severe drought stress, relative electricconductivity, MDA content, the activities of SOD, POD and CAT, the soluble sugar contentand the proline content increased at different levels in leaves at booting stage, flowering stageand grain-filling stage, while the soluble protein content showed different trends at bootingstage and flowering stage and increased at grain-filling stage; Root vigor decreasedsignificantly during the three growth stage. Besides, net photosynthesis rate, stomatalconductance and transpiration rate increased while intercellular CO2concentration decreasedat flowering stage and grain-filling stage.(2) Under moderate drought stress and the severe drought stress, the plant height, earlength, internode length below spike decreased; Spikelet number, grains per ear,1000-grainweight also decreased. What’s more, grains per ear and grain weight per spike showedsignificant differences between contrasts and moderate drought and severe drought. Droughtresistance indexes were same at the two different drought stress levels except forZhengmai366and Xinong509.(3) Based on the comprehensive indexes (D) and cluster analysis, the7tested cultivarswere divided into3groups. Jinmai47and Xiaoyan22belong to high drought resistance group,Aikang58, Xinong979and Xinong509belong to medium drought resistance group,Zhengmai366and Zhengmai9023, belong to low drought resistance group. In additional, atthe two different drought stress levels, the comprehensive indexes (D) significantly correlatedwith drought resistance indexes (P＜0.01).The effect of low temperature stress on physiological parameters and yield of winterwheat:(1) Under low temperature stress at jointing stage, compared with the control, relativeelectric conductivity(except for the Zhengmai366and Zhengmai9023) and proline contentshowed the trend of from increasing to decreasing, while the MDA content showed oppositetrend; The activities of SOD, POD and CAT and the content of soluble sugar increased atdifferent levels, and the content of soluble protein(except for the Zhengmai366andZhengmai9023)were increased. Under low temperature stress at booting stage, relativeelectric conductivity、MDA content、the activities of SOD, POD and CAT and proline contentincreased significantly while the soluble protein content decreased significantly.(2) Low temperature stress at both jointing stage and booting stage significantlydecreased grain yield and the number of grain per ear, but the effects on the number of spikeand1000-grain weight was less significant. Taken physiological parameters into account, low temperature stress at booting stage had a greater negative effect on the yield and physiologicalparameters than at jointing stage.(3) Based on the fuzzy mathematics method, the tested cultivars were divided into2groups: Xiaoyan22and Aikang58belong to high cold resistance group, the other3cultivars,Xinong509, Zhengmai366and Zhengmai9023, belong to low cold resistance group. This isaccordance with the production in this experiment.Analysis on genetic diversity of Xiaoyan22to its derived cultivars:A total of187alleles were detected among the tested materials, and the number of eachlocus ranged from2to5alleles with an average of2.6alleles. The polymorphism informationcontent (PIC) main value ranged between0.3047~0.5815, averaged at0.3884per primer.Genetic distance among the8materials varied from0.3091to0.7671with an average of0.5945, which indicated that the genetic diversity was smaller. The tested materials fell into2clusters by UPGMA analysis at the point0.55; which could reflect the relationship amongthem. The genetic similarity coefficients between Xiaoyan22and its sister line Xiaoyan22-2was0.73.In summary, it is an effective way to evaluate the wheat cultivars’ stress resistance(drought stress, low temperature stress) using principal component analysis and fuzzymathematics method combined the stress-related indexes with production after stress.Compared with other tested wheat cultivars, Xiaoyan22showed lower negative effects on thecellular membranes, higher antioxidation enzymes, osmotic adjustment and photosyntheticcapacity, which may be the major physiological traits to have a relatively higher productionafter the environmental stress. Besides, Xiaoyan22had a rich genetic background and someimportant chromosomal loci and regions which were related with important agronomic traits.This might be basic genetic features of Xiaoyan22as a core parent.