Study Of Seed Shattering Related Phenotypes And AnQ In Avena Nuda

Seed shattering is an important trait that needs to be considered during crop domestication and breeding,and currently severely affected the yield and grain quality in naked oat production.This study explained the mechanisms of seed shattering at the phenotype level,as well as the relationships between seed shattering trait and the morphology of florets thoroughly and systematically,via the identification of over 150,000 floret phenotypic data in two naked oat populations composed of 117 and 347 cultivars and lines,respectively.The seed shattering-related gene An Q was cloned and identified.Based on the phenotypic data of this research,the relationships between An Q and the phenotypic traits including seed shattering were studied by the development of molecular markers.Last but not least,GWAS was conducted to screen out the genes that closely related to seed shattering as well as seed shattering related traits.The results came out as follows.According to the correlation studies of 18 phenotypic traits including seed shattering,seed shattering in naked oat was not determined by the BTS(breaking tensile strength)of seeds,but was significantly related to 10 morphological traits of florets at one or more ecotopes(P<0.05),such as the width of palea,the width of lemma,and the thickness of the mid-spine of lemmas(average correlation coefficient being-0.27,-0.18,-0.16,respectively).Observations into the morphology of paleas also found that the higher capacity of the paleas to encapsulate the seeds,the lower seed shattering rate was observed.Conclusions can be drawn from the findings above that the width and area of paleas and lemmas affects seed shattering by altering the degree of encapsulation of the seeds,and the overall thickness at the bottom of lemmas affects seed shattering by regulations of the ability to withstand external forces and to avoid being opened.In this research,the homologous of gene Q were identified in naked oat chromosomes4 A,4C,and 4D,termed An Q4 A,An Q4 C,and An Q4 D,respectively.Haplotypes of An Q4 A,An Q4 C,and An Q4 D were identified by multiple comparisons of the the sequences in six naked oat cultivars.Two haplotypes were identified in An Q4 A and An Q4 C,and four haplotypes were identified in An Q4 D.An STS complementary dominant molecular marker was developed according to the sequential characteristics of the two haplotypes of An Q4 C.The correlation between the marker An Q4 C and seed shattering was not obvious(P=0.09),however it was significantly correlated to six phenotypic traits that were closely related to seed shattering.The marker accounted for 21.64%,15.94% and 14.60% of the total variance of seed cross-sectional area,palea width and lemma width,respectively(P=0.000),and 3.49% of the total variance of the seed/palea width ratio(P=0.02).The marker also accounted tor 2.60% and 8.58% of the total variance of the thickness at the middle and side of the lemma spine,respectively(P<0.05).These six traits were significantly correlated to seed shattering(P<0.05).A population of 116 oat cultivars were re-sequenced,and abundant SNP markers were obtained in naked oat genomes.Following GWAS analysis identified SNPs significantly correlated to the area and width of lemmas.Three candidate genes were identified subsequently.They were predicted RNA methyltransferase gene,predicted ribosomal protein gene,and predicted Glutathione S-transferase gene.The results would lay the foundation for further studies into the molecular mechanisms of seed shattering in naked oat.In addition to the research into the mechanisms of seed shattering,this study provided resources for germplasm developments of seed shattering resistance.Identification of the seed shattering traits of naked oat at the nine ecotopes revealed the distribution density of the population.five grades of seed shattering rate were designated accordingly: low(seed shattering rate being 0-0.03),medium(0.03-0.07),comparatively high(0.07-0.12),high(0.12-0.21),and very high(over 0.21).13 cultivars with low shattering rate were identified,which could be used for further studies and developments.Additional findings of value were witnessed in this study.A specialized zigzag pattern was observed in lemma cell wall of naked oat via microscopic observations.This jigsaw-like pattern could reinforce the connections between cells and add to its strength and toughness.Other than that,17 cultivars were found to present the morphology of Avena sativa or Avena nuda in the spikes at different ecotopes.Special traits were observed in cultivars Xia Naked Oat,Xiao Oat,and Wuzhai Naked Oat: the first florets presented Avena nuda-like traits,while the following florets presented Avena sativa-like traits in the same spikelet.This indicated the existence of hybrids of Avena nuda and Avena sativa in naked oat population,and the traits described were unstable.