Genetic Analysis Of Maize Inbred Lines Involved Ailien Chromatin And Gene Location Related To Prolificity With Molecular Markers

Maize is an important food and feed crop in the world today.The "domestication bottleneck" effect and the subsequent artificial selection for improvement reduce the genetic diversity on maize relative to the wild progenitors.Moreover,contemporary breeders prefer current,elite inbreds with known combining ability as sources for inbred development and for the improvement of hybrid performance,making maize genetic base narrower than before.It is unanimous that there is no breakthrough for maize improvement without germplasm enrichment and creation,so exploring and utilizing the wild relatives plays a key role in this strategy.Zea mays ssp.mexicana,an annual teosinte,is a wild relative of maize.It has some valuable traits,such as strong growth vigor,high protein content in the kernel and notable immune ability or resistance to multiple fungal diseases,making it beneficial to maize quality and resistance improvement.Ye515,an elite inbred line widely used in China,provided with good agricultural traits such as high combining ability and large kernel rows,however,it also has some disadvantages,such as imperfect kernel quality,high infection of maize stalk rot,maize rough dwarf disease and brown spot.We achieved some good introgression lines by combining different inbred and backcross with Zea mexicana as the male parent,Ye 515 as the female and recurrent parent.Among these lines,we chose the ones possessing prolificacy,long shank and big ears(named 1#,10# and 4# respectively)for cytological and molecular identification.And the primal location of prolificacy-relative gene was studied in our research.Cytological identification of these introgression linesFive samples were randomly selected from Ye515 and these three lines for karyotype analysis.The chromosome number was consistent with the euploid number of 20 and no numerical chromosome changes were observed.The C-banding polymorphisms were a result mainly of the presence/absence of particular bands. Variation was also observed for band size and staining intensity.The variations of arm ratios and kayotypic formula were obvious within and between these lines.Ye515 possessed 2n=16m+4sm of karyotypic formulae.Karyotypic formulae for line 1# and 10# were 2n=14m+6sm and 2n=12m+8sm.The C-banding of line 4# indicated the instability of its karyotype,because the number of C-bands was different in diverse samples,which suggested that line 4# was not pure in heredity after different inbred and backcross.GISH was used successfully to identify the alien chromatin.Hybridization signals were steadily detected.For line 1#,chromosome 4,7 and 8 existed six signals symmetrically on the terminal and subterminal regions of the long arm.For line 10#, chromosome 2 and 4,7 existed six hybridization signals symmetrically on the subterminal and terminal regions of the long arm.The positions of GISH signals were highly consistent with C-band.There were 7 hybridization signals in line 4#,among which 6 signals were detected symmetrically on different chromosomes,the last signal being located on one of the two chromosome 6.The position of signals was not symmetrical and the number of C-band was unstable in different samples indicated that line 4# was not pure after different inbred and backcross.Primal location of prolificacy-relative geneYe515(single-ear parent)and line 1#(multi-ear parent)were used as experimental material.The hybrid F₂ population between them was constructed from sexual crossing.Prolificacy of the F₂ population was determined by SSR-BSA (bulked segregant analysis)techniques.Among all of the 130 SSR marker pairs, which show polymorphism between Ye515 and line 1#,bnlg1779 showed coherence to the parents when PCR amplification has been carried out among the single-ear pond and multi-ear pond.Analyzing by Mapmaker Version 3.0,we found that genetic distances between bnlg1779 and prolificacy-relative gene was 13.99cM.Comparing with the published genetic linkage map,bnlg1779 was on the long arm of chromosome 3.The SSR marker pairs being polymorphic between Ye515 and 1# on chromosome 4,7,8 were analysed to find that line 1# possessed polymorphic bands comparing to Ye515 and ZM.The polymorphic bands were as follows:bands resemble to Ye515â‘ ,ZMâ‘¡,parents bands lean to Ye515â‘¢,parents bands lean to ZMâ‘£and new bands⑤.Among which②③④indicated the insert of ZM DNA. For line 1#,15 loci on chromosome 4 were analysed,6(40%)indicated the insert of ZM DNA;6 loci on chromosome 7 were analysed,2(33.3%)indicated the insert of ZM DNA;9 loci on chromosome 8 were analysed,the proportion was 2(22.2%).The distribution of these SSR markers was consistent with GISH signals.We used karyotype and GISH analysis to identify these introgression lines,and then we investigated genome variation as well as alien chromatin distributing. Through our study we provided some excellent materials and laid the basis for location and cloning of related genes.