| There are23basic genomes in the tribe Triticeae, and the H, P, St, and Y genomes are importantgenomes of this group. The H, P, St, and Y genomes in Triticeae are mainly found in some diploid andautopolyploid species, for example, Hordeum L.(H genome), Agropyron Gaertn.(P genome),Pseudoroegneria L.(St genome), and some allopolyploid species, for eaxmple, Roegneria C. Koch.(StYgenomes), Elytrigia Desv.(StE genomes), Elymus L.(StH or StHY genomes), and Kengyilia Yen et J.LYang (StPY genomes). In order to study the genetic evolution relationship among H, P, St, and Ygenomes, some diploid and polyploid species including H, P, St, and Y genomes, and their naturalhybrids were ananlyzed in our study using molecular cytogenetics, LTR sequeces analysis ofretrotransposons and so on. The main results as follows:1. A GISH-FISH method was first developed to distinguish the St, P, and Y genomes, and thekaryotypes of five individuals from population Z1925of Kengyilia grandiglumis Keng (2n=6x=42,StStPPYY) were analyzed. The results showed that there were structural polymorphisms in all of thechromosomes from the three individual genomes. The polymorphisms were mainly found in theterminal regions of chromosomes, and infrequently near the centromeric region. Of all thechromosomes,1P,1St,1Y,2Y,3St and3Y showed the highest polymorphisms. The polymorphismswithin the individual chromosomal structures provided important guidance on the collection,preservation, study and utilization of wild species in Triticeae.2. To investigate intergenomic rearrangements after polyploidization of Triticeae species and todetermine the effects of environmental factors on them, nine populations of a typical polyploid Triticeaespecies, Kengyilia thoroldiana (Keng) J.L.Yang et al.(2n=6x=42, StStPPYY), collected from differentenvironments, were studied using genome in situ hybridization (GISH). We found that intergenomicrearrangements occurred between the relatively large P genome and the small genomes, St (8.15%) andY (22.22%), in polyploid species via various types of translocations compared to their diploidprogenitors. However, no translocation was found between the relatively small St and Y chromosomes.Environmental factors may affect rearrangements among the three genomes. Chromosometranslocations were significantly more frequent in populations from cold alpine and grasslandenvironments than in populations from valley and lake-basin habitats (P<0.05). There is a significantpositive correlation between types of chromosome translocations and altitude (r=0.809, P<0.01). Thetypes of chromosomal translocations become more complex with increasing altitude, which indicatedthat environment play an important role in genome evolution.3. To investigate the effects of different altitudes on different P chromosomes involving inintergenomic translocations in K. thoroldiana, the two populations Z2538from4015m and Z2633from4710m were analyzed in our study. The results showed that P chromosomes involving in intergenomictranslocations are1P and7P chromosomes in population Z2538, while2P and5P chromosomes inpopulation Z2633, which indicated that the effects of environment on different chromosomes evolution of the same genome were different.4. To discuss formation mechanisms of polyploid species, three natural hybrids collected inTibet, which were named â…¢, â…£, and â…¤, were studied. Based on the fertility, genomes constitute, andmorphology and their accompanied species, it was inferred that â…¢ and â…£ were natrual hybrids betweenElymus nutans and Elymus dahuricus, and hybrid â…¤ was natrual hybrid between Elymus nutans andRoegneria breviglumis (2n=28, StStYY). â…¢ and â…£ were hexaploids hybrids including7translocationchromosomes separately, and hybrid â…¤ was pentaploid hybrid including6translocation chromosomesusing cytogenetics. Multivalent was mainly formed by St-Y chromosomes or large fragmenttranslocation chromosomes respectively. Although there were no significant differences among themean c values of these three hybrids (P>0.05), the c value of (St-Y) genomes was significantly higherthan that of (St-H),(H-Y), so closest relationship occur between St and Y genomes among the threegenomes, which is significant for study the origin and evolution of Y genome. The further analysissuggested that polyploid species become a stable and new species not by only one simple natrualhybridization and chromosomes doubling, but complex reticulate evolution.5. Some diploid and polyploid species including H, P, St, and Y genomes, allopolyploid speciesincluding St and Y genomes, and Brachypodium sylvaticum were used as materials and studied bymolecular phylogenetic analysis and copy numbers variation of LTR sequeces of retrotransposons. Wefound that some relationhip occurred among H, P, St, and Y genomes, which provided molecularbiology basis for further research on genetic evolution of different genome in Triticeae. |
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