Study On Improvement Potential Of Kernals Per Spike In Spring Wheat (Triticum Aestivum L)

Spring wheat is one of the improtant edible crops in Heilongjiang Provence of China. Recently,however, the planting area of spring wheat in this provence was descended from 2 million hactarsto less than 200 thousand hactars for the lower economic benefits than other crops such assoybean,corn and rice. The lower yield of spring wheat has become the main limiting factors forincreasing its benefits though the quality of the crop has been largely improved genetically. Theyield would be divided into three components e.g. spikes/hm~2,kernels/spike and 1000 grainsweight. Now 6-9 million plants/hm~2 reached to top of the normal wheat planting desity inHeilongjiang; 1000 grains weight of wheat was also restricted to 30-35 g by cultivars andenvironment in the province. So the kernels/spike became the bottleneck for high yield of springwheat.The diversity of genotypes in carbohydrate metabolism in the spikelets formation,the causeof the variation among genotypes in seed setting, the effect of N fertilization to seed settingpercentage of wheat cultivars and the relation between kernels per spike and 1000 grains weightwere studed in the trial for increasing spikelets and kernels in spring wheat. The results showed:. The significant differences among genotypes in the contents of both soluble totalsaccharinity and sucrose in plants were found in the process of spikelets differentiation in wheatand triticale, and the level of those two compounds in triticale was higher than that in wheat. Thedifference of sucrose content occurred among wheat cultivars after double ridge stage. A increaseof total spikelets was observed with the raise of sucrose in plant of wheat.No fructose was measured in the plants of wheat and triticale before the single ridge stage andafter the very stage the level of this ingredient was no different between the two species.2. The quicker rate of the elongated apex and single ridge stages, the longer of spikedeveloping and especially the double ridge durations in the process of the spike differenciationwould be advantage for increase of spikelets per spike in wheat.3. The period from embryo initiation to full filling of grain seemed to be the limit of grain setin spring wheat. The reduction of the embryo abortion would be the key of increase of seed set andfurthermore kernels of spike.4. The increase of the contents of both soluble total sugar and sucrose in the stem and leaves inthe period from embryo formation to 1/3 filling state and of the output amount of the same materials from the stem and leaves in the period from 1/3 filling to full filling states would reducethe embryo abortion effectively.5. The nitrogen fertilizer appliction could make improvement obviously in more florets andlower young embryo abortion. The florets of spike seemed to be affected by the sugar metabolismin leaves and dry-matter output from leaves. The higher the dry-matter output and amount ofsoluble total sugar,fructose and sucrose from leaves, the more the florets of spike in wheat. Theincrease of output of dry-matter and the soluble total sugar,fructose and sucrose from leaves wasobserved in the floret differentiation with optimum application of N fertilizer.The rate of the young embryo abortion could be influenced by the amount of soluble sugar andsucrose transportation from stem,leaves and flag leaf after embryo initiation. The embryo abortionreduced because of the increase of the output of those elements in the optimum N treatment.6. The relationship of grains per spike and 1000-grain weight might be varied among wheatcultivars in 3 nitrogen fertilizer treatments. The most kernels of spike presented in N1 in allcultivars. No diversity of 1000-grain weight of DongNong126 was found in all 3 N treatments. Thehighest 1000-grain weight of LongFu 9 was in N1 and that of Jia-T in N2. The varying amount ofdry-matter in the flag leaf had the most close relation to 1000-grain weight in the grain fillingperiod of wheat. The changing amount in stem had no influence on 1000-grain weight though itvaried largest. The key of increase 1000-grain weight of wheat was how to speed up the outputamount of dry-matter from flag leaf in the grain filling period.