Wheat Grain Yield And Quality Formation As Affected By Salinity Stress And Regulation Measures

The experiments were carried out at experiment field of Jiansu Provincial Key Lab of Crop Genetics and Physiology,Yangzhou University, and Jinghai Farm of Coastal Area Agricultural Research Institute from 2003 to 2006 to study the response of dry matter production and yield formation to salt stress, and the effects of salt stress on grain quality formation, nuitrition characteristics and flag leaf senecence in wheat, investigate the effect of cultivating measurs on grain yield and quality under salt stress. The relationship of soil salt and primary component contents with dry matter production, yield and its components formation, protein and its component contents, starch and its component contents was also analyzed. The major results were as follows.1. Effect of salt stress on dry matter production and yield formationThe results showed that under the condition of salt stress, dry matter accumulation amount, tiller number, plant height, LAI, and grain filling rate decreased, so effective spike number, grains per spike and 1000-grain weight declined which resulted in the decrease of grain yield. While there is no significant difference in grain yield and its components between control and salt stress treatments when the soil salt content was lower than 1.2656g/kg in field experiment or lopwer than 1.617g/kg in pot test. The relationship of soil salt and primary component contents with dry matter production and yield formation were studied. Soil salt was significantly and negatively correlated with tiller number, plant height, and grain yield. The ions manly affected yield components were Na+, SO42-, K+, and Cl-. The order of yield components affected by salt stress was effective spike number>grains per spike>1000-grain weight in wheat varieties Ningyan1 and Ningmai 9, however it was effective spik number>1000-grain weight> grains per spike in wheat variety Cangzhou6002.2. Effect of salt stress on grain quality traitsThe result indicated that grain protein and its component contents increased and protein accumulation content decreased with the increase of soil salt content. The effects of salt stress on grain protein content were different among different wheat varieties. The increase extent of protein content was greater in wheat with lower protein content than that in wheat with higher protein content, and the order of the increase extent among the tested varieties was Ningmai9>Cangzhou6002>Ningyan1.Dynamicas of grain protein and its component contents under the condition of salt stress was the same as normal growth condition. The changes of albumin, globulin and protein contents showed"V"type curve change, while gliadin and glutenin contents kept increasing after anthesis. The difference of albumin content among different salt treatments were the greatest on the 7th day after anthesis (DAA), while the differnece of globulin, gliadin, glutenin and protein contents were the greatest at maturity.The effects of salt stress on grain starch and its component contents were studied. Compared with the control, grain starch and its component contents increased a little with under lower salt stress, but decreased significantly under higher salt stress. Because the decrease rate of amylose content was greater than that of amylopectin content, the ratio of amylose to amylopectin decreased. Effects of salt stress on grain starch content were different among different wheat varieties. The order of the decrease extent was Ningmai9>Cangzhou6002>Ningyan1, which means that there was no correlation between starch content decrease content and salt stress resistant ablility among different wheat varieties.The differneces of grain starch and its component contents among salt content treatments were the greatest at maturity. The relationship between salt stress and grain protein and its component contents was studied. The results showed that soil salt, Na+, SO42-, K+, Cl- concentrations had significantly positive correlations with grain protein and its component contents. The relationship between salt stress and grain starch and its component contents was also studied. The results showed that soil salt and salt ion contents had negatively correlations with grain starch and its component contents, and the ratio of amylose to amylopectin. Wet gluten content and unit weight of the tested wheat varieties under lower salinity content had no significant difference with CK. Wet gluten content increased and unit weight decreased with the increase of soil salt content. Sedimentation value decreased in Ningyan1 and Ningmai 9, but increased in Cangzhou 6002 with the increase of soil salt content.With salinity stress, peak viscosity, trough viscosity, final viscosity, breakdown and setback increased. The changes of peak time and GT were different in different wheat varieties.3. Effect of salt stress on quality formation mechanismThe result indicated NR activity in flag leaves decreased after booting stage. NR activity chould be promoted in lower salt content, but restained in higher salt content. The sensitive degree of NR activity to salt stressin slat-tolerant varieties was lower than that in salt-sensitive varities. GS activity in flag leaves increased firstly after anthesis, then decreased gradually, and the appearance time of GS activity peak was different in different varieties. The effects of salt stress on GS activity were different in different wheat varieties, and which was not significan in salt-tolerant variety (Cangzhou6002), while was significant in Ningyan1 and Ningmai9. The changes of GS activity in grains decreased on the whole after anthesis. The effects of soil salt stress on GS activity were significant, and the decrease degree of GS activity increased with the increase of soil salt content, which had no significant difference among varieties.Soluble sugar content in grains decreased during filling stage. Soluble sugar content decreased rapidly on the 7～21th DAA and decreased slowly after 21th DAA in Ningyan1 and Ningmai9, while decreased rapidly on the 7～14th DAA and decreased slowly after 14th DAA in Cangzhou6002. The change trends of sucrose content in grains were different in different wheat varieties. Sucrose content increased on the 7～14th DAA and decreased after the 14th DAA in Ningyan1 and Ningmai9, while decreased on the whole in Cangzhou6002.The activities of key enzymes involved in starch synthesis (AGPP, SSS, GBSS) all showed a single peak curve after anthesis, and reached their maximum values on the 28th DAA, which decreased with soil salt stress. The effects of soil salt stress on AGPP, SSS, GBSS activities in different wheat varieties were different.4. Effects of salt stress on nuitrition characteristicsWith the increase of soil salt content, NPK uptake amount in plant decreased. Na content in stems and leaf sheaths, and leaf blades rose under salt stress. N content in stems and leaf sheaths declined with the increase of salt content, but N content in leaf blades declined only under high salt content. P content in leaf blades decreased with the increase of salt content in Ningyan1 and Cangzhou 6002. Lower salt content caused P content in leaf blades increased, while higher salt content decreaed P content in leaf blades in Ninmai 9. K content in stems and leaf sheaths, and leaf blades decreased only under high salt content. N/Na, P/Na, and K/Na ratios decreaed with the increase of soil salt content.5. Effects of salt stress on flag leaf senescence after anthesisThe results indicated that MDA content in flag leaves increased, while the activities of superoxide dismatase(SOD)and catalase(CAT) decreased, SPAD values in flag leaves after anthesis decreased with the increase of salt level. There was no significant difference in those physiological parameters between low salt levels and control, but significant difference was found between high salt levels and control. The response of wheat to salt stress varied with variety .The changing rang of senescence indices was smaller in salt-tolerant varieties than that in salt-sensitive varieties.6. The effects of cultivation measures on wheat grain yield and quality formation under salt stress.Increasing nitrogen application amount and seedling number could raise effective spike number per unit area. While increasing phosphohydrate applicationg amount could raise grain number per spike and 1000-grain weight. With the increase of nitrogen application amount and phosphohydrate appling amount, grain protein content rose, while starch and starch component contents declined. With the increase of seedling number, starch and starch component contents increased. With the increasing of nitrogen application amount and phosphohydrate appling amount, wet gluten, sedimentation value and test weight increased under salt stress.