Chromosome Variations Induced By Distant Cross And Irradiation In Triticale

Triticale is the first man-made and widely cultivated cereal crop.Due to the combination of the excellent characteristics of wheat and rye,it has the advantages of cold,drought and diseases resistance,but it is genetically unstable due to the combination of multiple genomes.Therefore,triticale also exhibits shortcomings such as poor fertility and shrivel grains,particularly,hexaploid triticale,being lack of D genome chromosomes,has poor processing quality.How to improve triticale is an important subject for further research and utilization of triticale.In order to select new triticale lines and series of triticale variants with significantly improved traits,in this study,distant hybridization of different ploidy triticales supplemented with ionizing radiation were used to produce secondary triticale and induce their chromosome variations and genome reconstruction.The main results are as follows:Oligonucleotide probe multiplex#5(ONPM#5)FISH previously developed by Cytogenetics Institute,Nanjing Agricultural University,China was used to construct high resolution karyotypes of hexaploid triticale Woh1084 and octoploid triticale Jinghuil,which could distinguish all triticale chromosomes after once in situ hybridization.Between the two parents,11 polymorphic chromosomes were identified on both wheat and rye chromosomes.To check chromosome variations in the progenies of Woh1084 × Jinghuil,220 plants derived from 44 F8 families were identified.Total three types of chromosome variations were found,which included numerical chromosome variations(NCVs),structural chromosome variations(SCVs)and complex chromosome variations(CCVs).For NCVs,their number ranges from 40 to 44,which involved 10 plants including 7 monosomics,1 double monosomics,and 2 trisomics;For SCVs,112 plants were identified which included 47 deletions,19 deletions plus unknown variations,and 46 unknown variations;For CCVs,31 plants were identified,which involved both number and structural variations.Statistical analysis showed that total 71 polymorphic chromosomes were identified in all F8 plants,among them,R genome chromosomes have the most(28 types),followed by A(19),B(15)and D ones(9).Most polymorphic chromosomes were produced by recombination between two parental types.Among all chromosomes in the secondary triticale lines,chromosomes 1 A,5A,2R,3R,and 4R tend to Woh1084,2A,4A,6D,1R,5R,and 6R tend to Jinghui1.No 3D and 5D were found,while 6A,1D,2D,4D and 7D were also present in low frequencies.Phenotype analysis found that the plant height of 64.3%of the hybrids was between the parents,17.9%was higher than Jinghui1 and 17.9%lower than Woh1084;the spike length of the hybrids were between the parents(100.0%);85.7%the spikelets number of hybrids was higher than two parents,14.3%was lower than two parents;71.4%of the number of grains per spike was higher than Woh1084,25.0%was between parents,and 3.6%was lower than Jinghui1.This result indicates that different ploidy hybridization of triticale can effectively induce genomic reconstruction and chromosome variations,which will facilitate improvement of triticale on grains and spikelets per spike.In order to produce more types of structural variations in secondary triticale,a F6 line 16CXJ121 derived from Woh1084 and Jinghui 1 were irradiated with 60Co-γ rays at a dose of 250 Gy and a dose rate of 0.9 Gy/min.Both M1 and M2 plants were identified.Among root tip cells of 57 M1 plants,72 variations involving R genome chromosome were identified.Among them,small fragmental translocations were the most(33.9%)followed by large fragment translocations(27.4%)>double centromere chromosomes(21.0%)>deletions and acentric fragments(9.7%)>ring chromosomes(6.4%)>intercalry translocation(1.6%).In 159 M2 plants derived from 52 M1 plants,23 types of variations involving R genome chromosomes(variation rate of 14.5%)were identified,including 18 SCVs(11.3%),3 NCVs(1.9%),and 2 CCVs(1.3%).This shows that irradiation combined with distant cross of different ploidy triticale will facilitate chromosome structural variations of the secondary triticale.