| Henan (HN) Province, located in southern part of the Yellow River, Huaihe River andHaihe River plain, is the most important winter wheat producer in China, with a yield of31million tons from an arable area of5.32million ha, occupied about21.9%and26.6%ofthe national total amount in2011. In central Henan province, water shortage is the mainfactor of limiting sustainable development of winter wheat production. Selecting cultivarswith high water use efficiency is an important way to relieve water competition and toensure the suistanable development of winter wheat production in the region. Theobjectives of this study were to analyze the changes of water requirement, agronomic traits,yield and its components and root features, to analyze the differences in water useefficiency and responses to different water stress conditions among winter wheat cultivarsreleased in defferent decades, and to understand the genetic and physiological mechanismsbehind these changes and differences. The results would be helpful for furtherimprovement of drought resistance and water saving capacity in breeding new winterwheat cultivars and improvement of optimal utilization of limited agricultural waterresources in central Henan.Six representative winter wheat cultivars released from early1950s to2007for centralpart of Hennan province were selected and tested during2010~2011and2011~2012growing seasons. With experiments carried out in leaching ponds under rain shelter andplots in field, water consumption features, photosynthetic characteristics, agronomic traitsand roots features under different water situations were studied. In leaching pondexperiment, three water situations were set as follows: control check (CK): Irrigating whensoil moisture was less than75%~85%of field capacity (FC); Mild water deficit (MD): lessthan60%~70%of FC; Serious water deficit (SD): less than45%~55%of FC. In fieldexperiment, three water situations were set as: W0: no irrigation after returning green stage;W1: only an irrigation at the jointing stage; W2: two irrigations at jointing stage and milkystage respectively. The main results were as followings:1. Water consumptions of winter wheat under different water situations can be ranked asCK＞MD＞SD. The highest grain yield for different winter wheat cultivars appeared inCK treatment, and the highest WUE occurred in SD treatment in pond experiment. Underfield experiment, water consumption can be ranked as W2＞W1＞W0, the highest grainyield was investigated in W2treatment, and the highest WUE in W0or W1treatment. Thepercentage of water consumption decreasing was obviously greater than that of grain yielddecreasing under water stress, which resulted in an increasing of WUE. There was a veryweak trend that water consumption decreased gradually, but an obvious trend that grainyield increased gradually with winter wheat cultivars changed, which resulted in aremarkable increasing thend for WUE of winter wheat. Data showed that the WUE increasing of winter wheat cultivars was mainly due to grain yield increasing. WUE ofmodern cultivars were generally higher than those of early cultivars under water stress.2. The greatest stage water consumption amount(CA), average daily water consumption(CD) and percentage of stage water consumption to total water consumption (CP) occurredin stage of jointing to flowering and stage of flowering to maturity, and the least valuesappeared in stage of overwintering to jointing. The CA, CD and CP of the modern cultivarswere less than those of the early cultivars in period of jointing to flowering and period offlowering to maturity in pond experment. The CA, CD and CP of early cultivars weregreater than those of the modern cultivars in period of jointing to flowering. Under fieldexperiment, the CA, CD and CP of early cultivars were less than those of modern cultivarsin period of flowering to maturity. The differences in CA, CD and CP between pondexperiement and field experiment were mainly caused by the differences in irrigation timeand irrigation quota for the two experiments.3. The chlorophyll content of flag leaf of winter wheat cultivar increased with itsreleased year, but the modern cultivars had no significant advantages in photosynthetic rateof flag leaf under all growing stages. In pond experiment, transpiration rate (Tr) of flag leafincreased at early and then decreased afterward during flowering to middle filling period.The winter wheat cultivars released in1970s and1980s had higher transpiration rates. Theintracellular CO2concentration (Ci) and stomatal conductance (Gs) of winter wheatcultivars tended to increase with released year. PSII maximum photochemical efficiency(Fv/Fm) of the modern cultivars was relatively greater than those of the early cultivars,which was related to a stronger ability of avoiding photoinhibition after flowering.4. The malondialdehyde (MDA) concentrations of the modern cultivars weresignificantly lower than those of the early cultivars under all water treatments. Themembrane lipid peroxidation was remarkably serious in the early cultivars. Soluble proteincontent in flag leaves of modern cultivars was higher in period of0to7days after anthesisand with a slower degradation afterward. Activities of superoxide dismutase (SOD),peroxidase (POD), and catalase (CAT) of the modern cultivars increased more quicklythan those of the early cultivars after flowering, which shown that the modern cultivars hadstronger capacity of scavenging oxygen free radical. This characteristic was helpful for themaintenance of stronger photosynthetic capability, and was beneficial to the compositionand transportation of arbohydrated, and laid a good physiological foundation for high1000-grain weight and grain yield.5. Under all water treatments, It were shown clearly that plant height was reduced,internode length shorten, and1000-grain weight, grain yield and harvest index improvedremarkably with the cultivar changed, but there were no significant differences in spikelength, diameter of low internodes, spike number per unit land, and grain number per spike.The plant height was decreased from100~120cm for early cultivars to50~70cm for modern cultivars, percentage of reduction was from25.6%to49.3%. The spike internodelength decreased from34.8~40.4cm to22.4~25.3cm, a reduction by35.5%~38.3%percent; The1000-grain weight increased from28.0~29.2g to46.4~47.6g, a63.0%~66.0%improvement, or a3.06~3.29g increment for each generation; The grain yield increasedfrom4069~5206kg·hm-2to6443~6880kg·hm-2, a44.4%~58.3%improvement, or a279~395kg·hm-2increment for each generation; The HI increased from0.27~0.32to0.35~0.37, a17.9%~35.8%increase; The WUE increased from1.15~1.42kg·m-3to1.78~1.81kg·m-3, a35.2%~55.3%improvement. The significant genetic improvement wasbenifitial to dry matter accumulation and translocation before and after anthesis. Themodern cultivars demonstrated a stronger ability for dry matter accumulation and optimaldistribution, which was a very important foundation of the increasing of1000-grain weight.The1000-grain weight and harvest index have a significant positive relationship with yieldimprovement.6. Root vigor was decreased, but root length density, especially for the roots rangingfrom0~0.05mm and0.5~2.0mm in diameter, and root tip number was increased underwater stress. The root vigor of the modern cultivars was higher than that of the earlycultivars in cultivating layer under water stress, which made modern cultivars with bettertolerance to soil drought. By fine root measurement, it was shown that modern cultivarshad greater average root diameter, and the percentage of length density of roots withdiameter more than0.45mm increased significantly under water stress, which was helpfulfor improving water uptake and utilization in cultivating layer and maybe the main reasonsof the drought tolerance improvement for the modern cultivars... |
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