Effect Of Cold-Water Stress At Grain-Filling Stage On Starch Accumulation, Yield And Quality Of Japonica Rice In Cold-Region

As a major rice area in cold region in Heilongjiang province, frequent occurrence of low temperature damage, has become one of the main factors restricting the development of rice in Heilongjiang Province. If suffering from the effects of the strong cold during the process of reproductive growth in rice, empty grain rate increased and yield serious decline.The grain-filling stage is one of the most sensitive period of chilling reaction, causing serious yield losses in the whole growth period of rice. And there is great influence on rice quality at the late sta ge. Therefore, it is great significance to research on yield and quality of japonica rice in cold-region. In this test, Dongnong 428, Songjing 10 and Longdao 7 were fieid-grown as material. Under field conditions simulating the natural low temperature by cold water irrigation ways, research on stage on starch accumulation, aerial part dry matter accumulation and distribution, rice yield and quality formation of japonica rice in cold-region under cold-water stress at grain-filling, to providing a theoretical basis for the production of high yield and quality of japonica rice in cold region in Heilongjiang Province.The follows are the main conclusions from this test:(1)At grain-filling stage, the cold-water stress significantly influence of dry matter accumulation of rice. Three varieties(Dongnong 428, Songjing 10 and Longdao 7) of the aerial part dry matter accumulation, the crop growth rate, Spike distribution decreased with the increase of cold water stress days, and there were significant differences among different treatments. Meanwhile, the initial growth potential, the maximum grain filling rate and the mean grain filling rate gradually reduced, delaying the grain-filling peak, the grain-filling time prolonged with the increase of cold water stress days. From three varieties responding to the cold-water stress, Songjing 10 has been most affected, Dongnong 428 has been least affected, Longdao 7 was in between.(2)At grain-filling stage, cold-water stress seriously impediment Hampered starch Synthesis and Accumulation of rice. The soluble starch synthase(SSS) and starch branching enzyme(SBE) activity of three varieties increases with the number of days after full heading, presenting a single-peak curve, soluble starch synthase(SSS) peaked at 16 days and starch branching enzyme(SBE) peaked at 21 days after full heading. With the increase of cold-water stress days, the declining degree of soluble starch synthase(SSS) and starch branching enzyme(SBE) activity increased gradually.After full heading, total content of starch, amylopectin content have decreased of three varieties, presenting a "S" curve. Under cold-water stress, total starch, amylopectin content of the cold-water treatment significantly reduce With the increase of cold-water stress days. Meanwhile, amylose content is also increasing, but amylose starch accumulation rate of differ ent cold-water treatment is different, the longer the cold-water treatment time, the higher the amylose content.At grain-filling stage, the sensitive variety responsing to cold-water stress on starch synthesis and accumulation is Songjing 10, the cold resistance variety is Dongnong 428, Longdao 7 was in between.(3)At grain-filling stage, rice yield has declined significantly under cold-water stress, with the increase of cold-water stress days, the declining degree of rice yield increased gradually, and there are significant differences between varieties and treatments. It is no significant influence on panicle length, effective panicle number, total grain number per spike, primary branch number, second branch number. It is extremely significant influence on empty primary branch number, empty second branch number, seed rate and housand seed weight. The decline of rice yield under cold-water stress at grain-filling stage is mainly due to seed rate and thousand-grain weight. From three varieties responding to the cold-water stress, Songjing 10 has been most affected, Dongnong 428 has been least affected, Longdao 7 was in between. Through the correlation it knows that there was significant or very significant positive correlation between dry matter accumulation at mature stage, spike distribution, effective panicle number, total grain number per spike, seed rate, housand seed weight and yield.(4)At grain-filling stage, the influence of cold-water stress on rice milling quality is to reduce brown rice rate, milled rice rate, head-rice rate. The influence of rice appearance quality is to reduce grain length-width ratio, increase the rate of chalkiness and chalkiness. The influence of rice cooking quality is to increase amylose content, reduce grain gel consistency.The influence of rice nutritional quality is to increase protein content, reduce lysine and tryptophan content. From three varieties responding to the cold-water stress, Songjing 10 has been most affected, Dongnong 428 has been least affected, Longdao 7 was in between.