| Awnness is an important trait in barley domestication,which is closely related to barley yield,much effort has been devoted to combining good characters from two-rowed and six-rowed varieties by cross breeding.The mechanism of awn inheritance help improve barley agronomic traits,but awn traits study has a long way to go.In this study,the interaction and genetic relationship of different awnness genes in barley,different germplasm were collected from two source(B series coming from International Atomic Energy Agency,E series coming from Fujian barley landraces),barley cultivars in order to identify the awn characters in the central and lateral row.Our results showed highly significant differences in the awn characters in the central row and in the lateral row in different cross combinations.Using six barley germplasm(B1,B12,B19,B33,E21 and E30),which differed in awnness trait of six barley cross combinations(E30×B1,E21×E30,E21×B1,E21×B33,E21×B12 and B19×E21)were made to F2 generation.According to the awn phenotype of parents,F1 and F2 segregation ratio,awnness genes interaction between awnlessness,normal hooded,subjacent hooded and long awn,and the relationship between them were revealed.Firstly,there was no segregation in F2,showing allelism between the two parents,such as the central row hooded gene between E21 and B33,and the central row long awn gene between E30 and B1.Secondly,the segregation ratio of 3:1 for F2 showed that one pair of gene differs between the parents.The segregation ratio obtained from combination(E30 x E21)was 3hooded:llong awn both in central and lateral row,which indicates that one pair of gene controls the phenotypic expression of the awns character in the combination of E30 x E21,and the 3:1 segregation ratio was also obtained from combination(E21 × B1)in central row and from the combination(E21 ×B33)in lateral row respectively,which means one pair of gene controls the hooded/long awn development in central row between E21 and B1,and one pair of gene controls the hooded/awnless development in lateral row between E21 and B33.Moreover,the segregation ratio obtained from combination(E21 × B1),(B19 × E21)and(E30 × B1)was 12:3:1 which revealed that two pairs of genes controls the phenotypic expression of the awns character in lateral row.However,the segregation ratio obtained from combination(E21 × B12)and(B19 × E21)were 48:15:1 and 48:12:3:1 respectively,which revealed that three pairs of genes controls the phenotypic expression of the awns character in central row,while combination(E21 × B12)segregation ratio was 192:48:15:1 indicating that four pairs of genes controls the phenotypic expression of the awns character in lateral row in the F2 generation.Besides the allelism relationship of allele genes,and non-allele gene interaction relationship was unveiled by the F2 segregation ratio.Dominant epistasis was the most common gene interaction in this study.The segregation ratio of 12:3:1 for F2 showed that one dominant gene is epistatic over the other pairs of genes,and the segregation ratio of 48:12:3:1 or 48:15:1 for F2 showed that one dominant gene is epistatic over the other two pairs of genes,and the segregation ratio of 192:48:15:1 for F2 revealed that one dominant gene is epistatic over the other three pairs of genes.By the combined analysis of F2 segregation ratio of different combinations,altogether,6 pairs of genes(A/a,B/b,C/c,K/k,L/l,M/m)were involved in awnness development,3 pair of them(B/b,C/c,K/k)were known in the barley morphological genes map,corresponding to Lksl,cal-a,Kapl.Dominant gene A determines the lateral spikelet awnlessness(Lsa),and gene A is dominant epistatic over K/k,L/l,C/c,and M/m,in the process of lateral awn development,and it might well be a new gene,being noted as Lsa.The dominant gene B,corresponding to Lks1,controls the awnlessness in the central spikelet,and this gene B is dominant epistatic over K/k,L/l,and if B is dominant epistatic over C/c and M/m,then it needs further investigation.The recessive gene c,corresponding to cal-a,is related to the subjacent hooded trait,but homozygote cc is not sufficient to develop the subjacent hooded awn,meanwhile,all aa,kk and ll are recessive homozygous for the subjacent hooded awn development,and the dominant genes C and L are duplicate dominant,the existence of C or L,with the homozygous recessive gene aa and kk,dominant trait-long awn,will develop.The dominant gene K,corresponding to Kapl,which determines the hooded awn development,and K is dominant epistatic over L/l and C/c,there was no significant relationship between K and M/m.L/l and M/m controls awn length,with a dominant gene corresponding to awn development.L is dominant epistatic over M/m in central row.Which May imply that L determine the long awn in central row,and M determines the awn development in lateral row.Since many reports were about awn length,the two recessive genes l and m might well correspond to the 2 known short awn gene,lks2 on 7HL and lks5 on 4HL.Furthermore,linkage analysis between the awnness gene(A/a)and row-type gene(Vrs1/vrs1)showed that the awnness and row type genes are relatively closely linked on chromosome 2H.The Bulk Segregant Analysis(BSA)by using molecular marker of simple sequence repeat(SSR)between the parents and the pools revealed that some primers have polymorphism between parents and between pools,such as Bmag0125and HVM54,indicating the closeness to the target gene,these molecular markers can be used furtherly in the F2 segregation group to map the Lsa gene on 2H.Nevertheless,Primer EBmac0415 on 2H have polymorphism between the parents but not between the pools which indicates that primer EBmac0415 may be far away from the target gene.Therefore this study concludes that there is a relationship between the awnness genes and row type genes in barley.Overall,6 genes are involved in barley awn development,new relationships between these 6 genes were unveiled,especially dominant epistasis,even multiple dominant epistasis is common is this study,and the lateral spikelet awnlessness gene Lsa might well be a new gene,and Lsa is linked to vrsl on 2H. |
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