Structural Chromosome Rearrangements And Polymorphisms Identified In Wheat By High-resolution Multiplex Oligonucleotide FISH

Common wheat(Triticum aestivum L,2n=6x-42,AABBDD)is one of the most important food crops in China.China has been the largest wheat producer in the world since 1990s.More than 2,000 wheat cultivars including 19 founders were released and grown in China from 1949 to 2000.To understand the impact of breeding selection on chromosome structural variations,high-resolution karyotypes of Chinese Spring(CS)and 373 Chinese cultivars were developed and compared through FISH(fluorescence in situ hybridization)using an oligonucleotide multiplex probe(pAs1-1,pAs1-3,pAs1-4,pAs1-6,AFA-3,AFA-4,pSc119.2-1 and(GAA)10)based on repeat sequences.Among them,148(39.7%)accessions carried 14 different structural rearrangement types,including three single translocations(designating T),eight reciprocal translocations(RT),one pericentric inversion(perInv),and two lines with a deletion combined with different single translocations(del/T).Five rearrangements were traced to eight founders with four being transmitted to more than three derivative cultivars via seven founders.This included 57 cultivars with perInv 6B that originated from Italian varieties Funo and Abbondanza and Chinese Fan 6 etc,47 with T 1RS-1BL from the Lovrin series,31 with RT 4AS·4AL-1DS/1DL·1 DS-4AL from Mazhamai and Bima 4,and three with RT 1RS·7DL/7DS·1BL from Aimengniu.Three other rearrangements were detected in more than two cultivars and are all reciprocal translocations occurred between chromosomes 4A and 1B,2A and 5B,and 1D and 4D.The remaining seven occurred in single accessions.In addition to structural rearrangements,there were 167 polymorphic chromosome blocks(defined as a unique signal patterns of oligonucleotide repeat probes distributed within chromosomes)identified based on FISH signal pattern and 59 blocks present in one or more founders.Some specific block types were present at high frequencies indicating selective blocks in Chinese wheat varieties.Based on structural rearrangements and block types,all cultivars and CS were clustered into four groups and 15 subgroups.Common block patterns occurred in the same subgroup.Thinopyrum bessarabicum Love(2n=2x=14,JJ),a wild relative of wheat,shows high salinity tolerance and multiple diseases resistance,is an important genetic resource for wheat improvement.A series of Th.bessarabicum 6J chromosome aberrations were produced by ph1b induction and radiation in previous studies.In this study,these aberrations were accurately identified by oligonucleotide multiplex FISH and genomic in situ hybridization(GISH).35 different alien chromosome lines were identified,including 2 homozygous whole arm translocations,7 homozygous small segmental translocations(including 1 homozygous interstitial translocation),3 homozygous large segmental translocations,4 homozygous deletions,2 homozygous telosomes,1 heterozygous small segmental translocation,1 heterozygous large segmental translocation,2 heterozygous deletions,3 heterozygous telosomes,1 heterozygous whole arm translocation and 9 complex translocations,which provides new genetic resources for identifying,mapping,transfer and utilizing of chromosome 6J of Th.bessarabicum.