Study On Pleiotropy Of Erect Panicle Type Japonica Rice And Difference Of Grains Quality At Different Positions Of Panicle Between Two Panicle Types Of Japonica Rice

Erect panicle type of Japonica rice is an important component of ideal rice plant type, which is closely related to population structure,yield potential and grain quality.Erect panicle type,which followed dwarf type and ideal plant type,is important morphological character development that Japonica rice adapts to high-yield requirement.But advance on genetic effects of erect panicle type rice has progressed slowly in recent years.It is still unclear whether erect panicle gene(EP) has other functions except that EP makes panicle shape erect.Erect panicle type can increase yield potential and meanwhile it can result in the change of grain weight and quality in the grains between different grain positions of panicle. Few studies have determined that how much are the effect of panicle type and grain position on the regularity degree of quality within a panicle.Genetic background of the near isogenic Lines(NILs) derived from Fengjin high generation of cross(F₁₃) and Liaogeng 5 analyzed by molecular marker method.Results showed the similarity of genetic background of NILs containing EP was 99.69%.It was a pair of rather ideal NILs.The effects of EP on agronomic traits of Japonica rice were studied by NILs.With typical japonica cultivars with erect panicle and curved panicle as the materials,the difference of rice grain quality and their position distributions within a panicle between two types panicle of japonica rice were researched.The main results were shown as follows:1 The erect panicle gene of rice also made plant height dwarf,panicle length short,leaf posture erect,leaves wide and short except that made panicle type erect.The varieties carrying dominant erect panicle gene had more leaf area index,higher chlorophyll content and rice biomass at 50%-heading and maturity stage.EP increased the number of large or small vascular bundles in panicle neck and the second internode from the top,which made grain-leaf ratio and translocation ratio of matter in stems and sheaths of erect particle varieties increase.2 Lodging resistance in different genotype rice cultivars were difference.Index of lodging at the 3^rd and 4^th internode in erect panicle cultivars carrying EP was significantly decreased,which resulted from its related traits such as lower plant height,larger internode thickness,larger area of cross section and wall thickness,higher dry weight of culm,leaf sheath,the dry weight of culm wall and internode per unit.3 EP increased the number of secondary branch on primary branch,consequently EP increased total number of spikelets and fertilized spikelet number on secondary branch.EP could raise yield by increasing total number of spikelets,total amount of fertilized spikelets, grain density and sink size within whole panicle.EP could decrease filled grain rate,spikelet fertilization rate,1000-grain weight and grain filling rate within whole panicle.EP increased especially yield from F₁ hybrids of japonica rice in the heterozygous genetic background.EP increased secondary branch number and grains on the secondary branches at the middle and base parts of a panicle.In erect panicle cultivars,panicle trait index was reduced,ear shape compacted and grain density at the base part of a panicle increased.4 Difference of grain weight-increasing process between two different genotype cultivars mainly presented difference of the 2^nd and 3^rd grain positions of secondary branch at lower part of rice.The grains positions of erect panicle cultivars had longer filling time and slower grain weight-increasing process which presented the characteristic of slow-fast-slow-fast-slow.The grains positions of curve panicle cultivars had relatively stable filling rate and the grain weight of these positions was at its most.Grain filling speed and process of erect panicle cultivars was slower than that of curve panicle cultivars,which resulted from a large amount of grains,especially inferior grains,on the secondary branches at lower part of erect panicle cultivars.5 The expression of EP began from seedling's establishment.The difference mainly presented plant height,leaf morphology and plant dry weight.The physiological mechanism which NILs differenced in morphological traits were that the contents of endogenous gibberellic acid(GA₃),abscisic acid(ABA),auxin(IAA)and cytokinins(ZR) differenced in each growth stage.Change of plant height exceeded change of panicle type after NILs in the shooting stage were separately treated with various concentration of exogenous GA₃ and paclobutrazol(PP₃₃₃).The effects of ZF₁₃ carrying dwarf gene and WF₁₃ carrying erect panicle gene on the two kinds of hormones were difference.6 Panicle type had little correlation with grain weight and seed setting rate of cultivars. The order of grain weight and seed setting rate among different grain positions was as follows: primary rachis>secondary;rachis top >middle>bottom rachis.The significant difference was found in grain weight among grains located on different rachises(primary and secondary rachises) and panicle position,i.e.top,middle,and bottom.The fourth to sixth grain of primary branch showed the highest grain weight and seed setting rate,the second grain the lowest.The first grain of secondary branch showed the least grain weight and seed setting rate,the second grain the greatest.The difference of grain weight and seed setting rate at different grain positions in erect panicle was higher than that in curved panicle.7 Panicle type had considerable influence on PC,AC,TQ at the different parts of panicle, for erect panicle cultivars,PC and AC increased with the grain position from the upper to the lower parts,while TQ showed reverse trend;for curved panicle ones,PC and AC showed no regular trend,but TQ was the same as that of erect panicle culfivars.In the same panicle,the PC of secondary branches was higher than that of primary branches,while AC and TQ behaved reversely.In the same rachis branches,the 2^nd and 3^rd grain of secondary branch at lower part had higher PC and lower TQ,the 1^st to 6^th grains of primary branch at mid and upper part had lower PC and higher TQ,no rule was found for AC at different grain positions of panicle.The difference of referred quality traits at different grain positions in erect panicle was higher than that in curved panicle,resulting from higher grain density in erect panicle. Results from this study will facilitate erect panicle cultivars in rice breeding for quality in Northeast China.8 Panicle type of Japonica rice had direct relation with milling quality of the grain. Milling quality of the grains for curved panicle cultivars was better than those of erect panicle ones.The indexes of milling quality of the grains on a primary branch were better than those on a secondary.The indexes of milling quality of the grains on a primary branch at bottom part were better than those at top part,but the grains on a second branch showed reverse trend. The milling quality of the spikelets that flowered earlier was superior to those flowered late. The change in milling quality was very identical with the following sequence.The significant difference was found in blown rice percentage,milled dee percentage and head rice percentage among grains located on different rachises(primary and secondary rachises) and panicle position,i.e.top,middle,and bottom.Positional variations in blown rice percentage for curved panicle cultivars was greater than that of erect panicle ones.While positional variations head rice percentage showed reverse trend.Positional variations in milled rice percentage varied with cultivars.9 Panicle type of Japonica rice had direct relation with brown rice shape.Brown rice shape for curved panicle cultivars was better than that of erect panicle ones.The indexes of brown rice shape on a primary branch were better than those on a secondary.The indexes of brown rice shape on a primary branch at top part were better than those at bottom part,while the grains on a second branch showed reverse trend.The brown rice shape of the spikelets that flowered earlier was superior to those flowered late.The significant difference was not found in length-width ratio and length-thickness ratio among grains located on different rachises(primary and secondary rachises) and panicle position,i.e.top,middle,and bottom. Positional variations in length-width ratio for erect panicle cultivars was greater than that of curved panicle ones,while positional variations in length-thickness ratio varied with cultivars.10 Particle types of japonica rice had no direct correlation with chalky grain percentage (CGP),chalkiness degree(CD) and transparence degree(TD) in the grains between the six japonica cultivars tested.All primary branches on a panicle were evenly divided into three parts of the upper,middle and basal.The grains were numbered as 1 to 6 on a primary branch and 1 to 3 on a secondary branch from the top to base.Generally,CGP and CD on the branches at the basal part of a panicle exhibited the greatest,at the middle part the middle, and at the upper part the least.CGP and CD for the grains on a secondary branch were greater than those on a primary branch at the same part of a panicle.TD was just the opposite.CGP and CD for the grain 1,5 and 6 on the primary branch showed the lowest,the grain 2 and 3 the highest.CGP and CD were the least for the grain 1 and the greatest for the grain 2 on a secondary branch within a panicle.Type panicle of japonica rice was not directly related to appearance quality of cultivar.The variation in appearance quality of different grains within a panicle was closely related to the flowering order of rice grains on the rachis branches.11 Panicle types of japonica rice had no direct correlation with fatty acid,albumin, globulin,prolamin,and glutelin content in the grains between the six japonica cultivars tested. Generally,fatty acid,globulin,prolamin,and glutelin content on the branches at the basal part of a panicle exhibited the greatest,at the middle part the middle,and at the upper part the least.Albumin content was just the opposite.The contents of albumin content,prolamin and glutelin for the grains on a secondary branch were greater than those on a primary branch at the same part of a panicle,while fatty acid and globulin content showed reverse trend.The variation in soluble protein and fatty acid content of different grains within a panicle'was closely related to the flowering order of rice grains on the rachis branches.The variation of protein content varied with soluble protein profile.The significant difference was found in fatty acid and soluble protein content among grains located on different rachises(primary and secondary rachises) and panicle position,i.e.top,middle,and bottom.Positional variations in fatty acid and soluble protein content of the grains between the six japonica cultivars tested varied with cultivars.12 Panicle types of japonica rice had no direct correlation with RVA profile parameters of rice cultivars tested.Starch viscosity characteristics for the grains on a primary branch were better than those on a secondary branch at the same part of a panicle.Starch viscosity characteristics for the grains at top part were better than those at middle and bottom parts. The variation in starch viscosity characteristics of different grains within a panicle was closely related to the flowering order of rice grains on the rachis branches.Starch viscosity characteristics for the grain 1,6 and 5 of the spikelets that flowered earlier were superior to those for the grain 2 of the spikelets that flowered late.The significant difference was found in RVA profile parameters including peak viscosity,hot paste viscosity,breakdown,cool paste viscosity,setback,consistence,gelatinization temperature and peak time among grains located on different rachises(primary and secondary rachises) and particle position,i.e.top, middle,and bottom.Positional variations in RVA profile parameters of rice varied with cultivars.13 The results of a single factor correlation analysis showed that TQ at different grain positions within a panicle had significant positive correlation with grain weight,blown rice percentage,milled rice percentage,head rice percentage,grain length,grain width,ratio of grain length to thickness,transparence degree,globulin content,gel consistence,peak viscosity,hot paste viscosity,breakdown,cool paste viscosity and consistence in the grains, and had significant negative correlation with chalky grain percentage,chalkiness degree, albumin,prolamin,glutelin,total protein,and fatty acid content,setback,gelatinization temperature,and peak time in the grains,and had little correlation with length-width ratio and amylose content in the grains.RVA profile parameters and milling quality of the grain showed most significant correlation than other traits with cooking and eating quality of rice at different grain positions within a panicle,while nutritional quality and grain shape showed lower correlation with cooking and eating quality of rice.