The Research Of Characterizations And Gene Mapping Of A Brittle Stalk Mutant Cef2 In Rice

Brittle culm mutation in rice is refers to the haulm brittleness increased mutation,which is a common rice mutation type.It has developed into a kind of important germplasm resources because of its good mechanical strength,the easily found identification in the field of brittleness character,straw easily crushed,high germination rate and genetically modified.The change of the stem mechanical strength is the main reason of the brittle rice mutation,which directly affect the crops lodging resistance properties of the mature period.Physical mutation is an effective and efficient way to generate brittle culm mutants nowadays.In this article,we created seven kinds of stem brittleness mutants in different degree changes of rice by heavy ion irradiation and analyzed stem cell wall composition change and the influence of the relationship between bending force and straw crushing.We found a mutant which showed no brittleness difference during vegetative growth or early filling stage but significant brittleness was observed during mature period,cef2,generated by heavy ion irradiation of Yang Jing 113.We focused on the potential mechanism of a brittle stalk mutant with temporal specific expression of cef2.We analyzed agronomic traits of cef2,the breaking resistant force of different growth stage,cell wall physiological and biochemical components,lodging characteristics,the genetic mutation analysis,the control of rice stem brittle mutant genes for the positioning of the research.The results are as follows:The results of different levels of brittle stalk mutants research:1.The performance of brittleness in mature period is more obvious than that during vegetative growth or early filling stage and the late appraisal is more accurate;2.Stalk brittle degree is different in different mutants.The cell wall main components are in differences.The greater the difference breaking resistance,the bigger the main cell wall components;3.Culm breaking resistance and cell wall components correlation analysis showed that influence of rice culm brittleness expression is mainly the content of cellulose,the higher the cellulose content,the greater the bending force of stem,the stronger the flexibility.Our result suggested that the correlation factor R=0.937(P<0.01)between cellulose content and flexural strength in brittle culm mutants with different background.Hemi-cellulose and lignin content in the stem are negatively correlated with breaking-resistance,the correlation coefficient is-0.86 and-0.21 respectively.4.We identified a brittle culm mutant cef2 mature period performance,which own high yield,low lodging index and easily crushed.Cef2 straw have high cellulose degradation efficiency than wild.type Yang japonica 113(yj113).The result of study in brittle stalk mutant ceJ2:1.The identification of brittleness character in the field of cef2:Brittle stalk characteristic of cef2 mutant is not expressed in the whole stage.The happening of brittleness is in about two weeks(15 days)after heading,with the increase of rice maturity brittle characteristics performance more obvious.We can find the time node of brittleness by the judgment with hand breaking the stalk in the field and ceJ2 mutation show the fragile characters of time expression specificity;2.Agronomic traits of cef2:The plant height,spike length,spike grain number per spike of cef2 mutant did not show significant difference compared with its wild type,but the tiller number and seed setting rate increased which the two are one of the important traits in yield components that suggested cef2 has better yield potential;3.The breaking-resistant strength analysis during different periods of cef2:The breaking-resistant strength of the second internode base were determined in different growth period of rice(jointing stage,heading stage,filling stage and mature stage).The flexural strength of cef2 mutant significantly smaller than the wild type,with the increase of maturity,the gap has been increased.The gap from 1.15 N from heading stage to maturity of 2.36 N,this is also consistent with the results of field observation field;4.The main cell wall components analysis of cef2:The main stem cell wall components of cef2 mutant show no difference in the change of different periods(jointing stage,heading stage and maturity).The stem lignin,inorganic salt,cellulose and hemicellulose content in mature stage,mutant cef2 were 8.65%,8.79%,23.21%and 8.79%respectively and the wild type jy113 were 8.88%,8.34%,30.62%and 8.88%respectively.Hemicellulose content of cef2 increased significantly,the cellulose content decreased significantly while lignin and inorganic salt show no obvious difference compared with wild type.5.Soluble sugar content in the stem analysis in different period of cef2:The soluble sugar content in the stem of cef2 with the development of the reproductive process show the first trend and the difference with wild type jy113 is bigger at later time.Content in mature stage was reduced by 33.6%than yj 113;6.The lodging characteristics analysis of cef2:We use lodging index for comprehensive evaluation of lodging risk.The mutant lodging index is less than the critical value to the standard of 200.It proves cef2's lodging less risky;7.The genetic analysis and gene mapping cef2:Genetic analysis showed that themutated phenotype of cef2 was controlled by a recessive gene.The cef2 gene was mapped on rice chromosome 3 by using map-based cloning method,and the genetic distances from the gene to the linked SSR markers RM3586 and RM487 were 5.6cM and 1.4cM,respectively.