| Spring wheat is the major crops in the arid region of northwest, north and Qinghai-Tibet of China and mostly distributed in dryland, therefore the drought is the major constraint to agricultural production. With the development of breeding and cultivation technology, spring wheat in northwest had acquired significant achievement on modifying their characteristics. and the environment in these region had totally changed and the yields of spring wheat increased a lot. But how to make yield higher in base of high yield, which was searched from improving planting environment and breeding fine varieties. So, studying on the genetic difference of yield, quality traits and resistance index in the arid region of northwest, north and Qinghai-Tibet of China, it will reveal the effects of genotype, environment and their interaction on crop growth, to provide evidence for breeding improvement and cultivation regulation. Difference is foundation of development, and it will supply developing space and potential for breeding improvement and cultivation regulation.The data of spring wheat regional trials on rainfed farmlands in 2002-2007 were analyzed with 35 cultivars (or lines) and 20 sites involving the eight provinces in the north of china, i.e. Shaanxi, Gansu, Ningxia, Qinghai,Xinjiang, Shanxi, Hebei , Inner Mongolian and Tibet. The sites were located within 29°20′N lat to 43°25′N lat, 84°42′E long to 114°42′E long with a range for annual precipitation(AP)of 300-580 mm, precipitation in the growing season (GP) of 87.6-523.1 mm , altitude of 950-3837 m , average annual temperature (AT) of 2.6-9.0℃and annual accumulated temperature (≥10℃) (AAT) of 1979-3732℃The effects of genotype(G),environment(E),genotype×environment interactions (GEI) were studied and variety stability were analyzied with AMMI, Shukla and other models. The main results are as fallows:1. Analysis on muti-year, multi-site and multi-variety showed that G, E and GEI had significant impact on dryland spring wheat grain yield per unit area, which indicated that the yield difference arised from environment were larger than the G and the GEI, and GEI affecting yield were larger than the genotypes. The G, E and the GEI accounted for 87.28%,2.0% and 10.33%of yield difference, respectively. The environment difference, including the test site environment and environment between years, based on same sites , the same cutivar and the same year across the trials indicated that yield and agronomic traits of site affecting yield were larger than that of years. The varience of site×cultivar,cultivar×year and site×cultivar×year were extremely significant. And among them site×cultivar was the first, site×cultivar×year was next, cultivar×year was the last, which accounted for 7.23%,0.16%,2.39%of sum of total treatment squares, respectively. Adaptation percentage to all sites(APS)between varieties was totally different up to 5.5 times. 33.67% of total tested varieties was high adaptability (above 60%). There will be great potential of dry-land spring wheat yield in northwest regional trials through optimized regulating plant environment, the planning of advantage region distribution and rational cultivar distribution.The AMMI model explained more variation caused by the GEI than linear regression model (LRM); the three significant interaction principal component axes (IPCA) accumulatively explained 84.03% of variation by the GEI , while LRM just explained 40.15% of those. Rank-correlation coefficient between yield and some stability parameters were significant.2. A major goal has been to develop stable high-yielding cultivars. The existence of GEI is a major factor affecting stability,which was low as their interaction was high. The analysis of AMMI model showed that: the stability among different varieties was of big difference, the stability parameter (Di) could be 4.3 times between the highest and the lowest, whereas that of the Dj between the maximum and the minimum value of the sites was up to 8.7 times. So,it is extrimly important that choosing a suitable site for identification of best cultivar and regional trial.Shukla and AMMI model as well as several other models, the results of analysis on stability are very consistent and reliable. As for AMMI model, the former three notable IPCA explained 84.03 percent of total variance, and with linear regression model, it only explained 40.15 percent of GEI square averagely, and which showed that AMMI model is more effective than the traditional linear regression model to GEI analysis.3. The correlation between Dj and seven environmental factors were shown that Dj were significantly correlated with annual average temperature(AT)(-0.535**),annual accumulated temperature(AAT) (≥10℃)(-0.430**),Frost-free days(FD) (-0.420**),altitude(0.371**),annual precipitation(AP)(0.282**) and precipitation in the growing season(GP) (0.382**),while were nonsignificantly correlated with Annual sunshine duration(Sun).4. In northwest area, the most common factor which caused low yield was water deficit. Drought resistance coefficient (DRC)was calculated to determine the extent of drought tolerance or susceptibility of each cultivar. The differences of DRI were significant; the difference of the DRI between the maximum and the minimum value of varieties was 2.42 times. whereas that of the Drought resistance index (DRI) between the maximum and the minimum value of the cultivar was up to 37.93times. In modern genotype, the best and better level of DRI accounted for2.86%, 8.57%of total genotype, respectively.the rest are under this level.Analysis of variance for the grain yield in multi-environment trials showed that the DRC reflected that thousand-kernel weigh(TKW) was the most stable or insensitive to water change . DRC of the traits was as below: TKW(0.9409)>spikes per unit area(SPU)(0.7745)>plant height(PH)(0.7668)>kernels per spike(KPS) (0.6791)>grain yield,(0.6373);however, Correlation between Di and DRC of agronomic traits indicated that the Di of genotypes was significantly correlated with DRC of SPU(-0.337*)>yield under drought-stressed (-0.378**)>DRC of PH(-0.370**)>Grain yield (-0.368**)>DRC of KPS(-0.319*)>yield nonstressed(0.106)>DRC of KTW(0.075)。the above indicated that the environment affecting the yield was through affecting the ear number per unit area and seed number per spike of wheat.High kernel weight by plant breeding will be the breakthrough point of high yield of dry-land spring wheat in the arid region of north west, north of china and Qinghai-Tibet china. Higher crop performance depends on the stong stability of cultivar with high yield.5. A great difference of the yield among modern genotypes of Dry-land Spring Wheat across the arid region of northwest, north and Qinghai-Tibet China were found the mean yield was 2471.03 kg·hm-2(range 318.6～3028.02 kg·hm-2), and the difference of the yield between the maximum and the minimum value of genotypes was 2.30times. Correspondingly, for 20 sites mean yield was 2467.40 kg·hm-2(range 392.61～6424.72 kg·hm-2),and the difference of the yield between the maximum and the minimum value of genotypes was 10.53times. On the whole, Although effect of environment was larger than genotype, the differences among genotypes for grain yield were significant in same sites. Plant breeding will improve the yield potentially.In addition, the mean of the genotypes tested for some important performance traits in all experiments are cited as below: TKW of 39.65 g(range 29.35～50.01 g),KPS of 29.12(18.7～33.58),SPU of 341.17 spikes·hm-2(222.75～375.75 spikes·hm-2),PH of 81.71cm(range 65.59～99.17cm),GPUE of 9.45 kg·hm-2·mm-1(range5.55～11.84 kg·hm-2·mm-1),stability times of 2.74min,maximum difference of 5.8min(rang 0.7～6.5 min),Protein scontent of 5.5%and maximum difference of 6.5%(range 11.25～17.8%)。Control cultivar Dingxi 35 was used in all trails in 6-yr, which may reflect the differences of the trial years or the sites more accurately basing the identical genotype, While its TKW of 20 sites varied from 31.45～46.29g, the KPS from 14.40～48.0, the SPU from 239.10～532.65 spikes·hm-2, the PH from 59.28～120.97cm, the GUPE form s1.52～27.2 kg·hm-2·mm-1.6. Rank correlation coefficients between yield and 7 factors of environment were significant. Yield had significantly correlated with GP(0.408**),AP(0.379**),Altitude(0.304**),FD(-0.373**),AAT(-0.427**),AT(-0.441**),Sun(0.105).The analyzing of correlation factors indicated that wheat yield was related to SPU,KTW, KPS,the corresponding correlation coefficients were 0.684**,0.453**,0.089, respectively, while were nonsignificantly correlated with KPS. It indicates that contradiction between individuals and groups of modern genotype was not outstanding. SPU and KTW was in synchronous improving scope, the high-yielding breeding restriction was relatively little. in the arid region of northwest, north and Qinghai-Tibet of China. |
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