Stress Effects On Starch Characters And Synthetase Gene Of Triticale

Triticale, a man-made cereal crop developed from a cross between wheat and rye, inherited the excellent characters and high yield of wheat and strong resistance of triricale, and it has good forage value、ecological value and industrial value. As the area of arid, semi-arid and high salt is increasing annually, thus the study on triticale in response to drought and salinity stress is helpful to understand the resistant ability and its effects to triticale characters. It is very important to probe and exploit the triticale potential, and it provide base on the forage production and ecology protection of triticale.Gradient drought and salinity stress were applied in the study and the stress started at5days post anthesis, drought stressis control, low water stress, moderate drought stressand severe drought stress(SWS55-60%). Salinity stress included control, low salinity stress, moderate salinity stress and high salinity stress, respectively. the relative express of starch synthetase gene, starch biomass, starch composition and starch morphology were determined and observed by physiology determination and real time PCR. The results showed:Starch synthesized of three triticale varieties (AC Certa, AC Ultima and Blue Alta) under drought stressreduced the population of small granules and had an increased ratio on A-type and B-type granules and there are pits on the starch granules in response to moderate and severe water stress. Triticale was treated with SWS led to a significant reduction in biomass, seed weight and starch contents (P<0.05) and the decrease values of starch content were reach to42-55%. Such decrease was associated with the reduced expression of starch synthesis genes at19days of water stress, and the decrease of SSI, SSⅡ and SSⅢ genes at19days of light and severe water stress. MWS favoured an increase of amylose content in triticale starch (P<0.05), which was accompanied by a significant up-regulation of GBSSI expression, and a significant up-regulation of GBSSII at31days of moderate water stress. An inverse relationship between drought stressand a range of starch gelatinization temperature was observed and MWS decreased the peak temperature (Tp) and increased the enthalpy (P<0.05). The expression model of ISA, SS and SBE genes is similar, their expression were significantly up-regulated at19days moderate water stress, and significantly down-regulated at19days light and severe water stress. Triticale starch synthesized under salinity stress showed a decreased population of small granules and an increased ratio on A-type to B-type granules with the salinity stress increasing, and there existed some pits on the starch granules in response to moderate and severe salinity stress. A reduction of seed weight and starch content of three triticale varieties was observed under salinity stress and the values were decreased by9-42%under MSS and18-51%under HSS (P<0.05). Such decreases were associated with the reduced expression of AGPase gene at19and31days under salinity stress (DUS). MSS and HSS favored an increase of amylose synthesis in triticale starch (P<0.05), which was mainly correlated with a significant up-regulation of GBSSI gene expression at7and19days under moderate and severe salinity stress, and significant up-regulation of GBSSII gene at19and31severe salinity stress. MSS and HSS decreased the peak temperature (Tp) and increased the starch enthalpy and an inverse relationship between salinity stress and a range of starch gelatinization temperature was observed (P<0.05). Light salinity stress inhibit the ISA gene expression at different developing stage, and the ISA gene expression was significantly up-regulated at19days of high salinity stress. The expression of ISA, SBEIIa and SBEIIb genes was significantly up-regulated at31days of moderate salinity stress, while was significantly down-regulated at31days of light and severe salinity stress.In the study, the starch synthetase genes during triticale seeds developing stage, starch granule morphology, starch composition and starch physicochemical characters were completely studied in response to water and salinity stress, it proclaimed the effects of water and salinity stress on starch synthetase expression and intergenic interaction, and the effects on starch composition and yield.