| Oat (Avena L.) is a kind of crop widely cultivated around the world for both food and forage. Itwas ranked at the sixth top place in planting area and production in the world, after wheat, rice, corn,barley and sorghum. Avena L. contains nearly30species, including diploid, tetraploid and hexaploidspecies. The aim of this study is to analyze different ploidy species of oat germplasm with karyotypeanalysis and SSR markers. The main results were summarized as follows:1. The karyotypes of30accessions of oats (22accessions were introduced from abroad, the otherswere from China) were characterized with karyotypic analysis. The results showed that30accessions ofoats contained the diploid species, tetraploid species and hexaploid species.The karyotypes of all diploidspecies of oats were symmetrically2A,which indicated that the diploid species were relatively primitivein evolution. However, they had different karyotype formulas, A. strigosa:2n=2x=14=10m+4sm(2SAT),A. hispanica:2n=2x=14=10m+4sm(2SAT), A. brevis:2n=2x=14=6m+4sm+4st(2SAT), A. nudabrevis:2n=2x=14=8m+4sm(2SAT)+2st. Compared with the karyotype parameters, the cultivated species A.strigosa was more advanced in evolution than the other three wild species A. brevis, A. hispanica and A.nudabrevis.The karyotypes of all tetraploid species of oats were also symmetrically2A. The karyotypeformula of an unknown tetraploid specie was2n=4x=28=16m(2SAT)+12sm,which was the same with A.maroccana. Therefore, the unknown tetraploid specie might be A. maroccana due to the similarkaryotype parameters. Compared with the karyotype parameters, A. maroccana was more advanced inevolution than A. murphyi.All the hexaploid species of oats had different karyotype formulas:A. sativa:2n=6x=42=22m+20sm(2SAT), A. fatua:2n=6x=42=24m+18sm(4SAT), A. nuda:2n=6x=42=24m+18sm (2SAT), A. sterilis:2n=6x=42=24m+16sm(4SAT)+2st. The karyotypes of the hexaploid cultivated species A. sativa, A. sterilisand A. nuda were2B, which was more advanced in evolution than2A of the wild species A. fatua.Moreover, the analysis of other karyotype parameters indicated that A. fatua was a relatively primitivespecie.Through the analysis of the karyotype formulas and the karyotypes of the different ploid species, itwas found that chromosome asymmetry became large with the increase in ploidy, and the2A type ofkaryotype also became more asymmetric2B type. So the higher of ploidy, the more advanced inevolution, which supported the conclusion that the polyploidy is a trend of evolution.2. The genetic variation of35accessions of oat were analyzed using SSR. As UPGMA clusteringrevealed, all35accessions of oats were divided into three categories corresponding to three differentploidies, and different species of each ploidy were also separated at certain genetic similarity coefficient.It can be seen that the tetraploid species had a closer genetic relationship with the hexaploid species andthe diploid cultivars and wild species were apparently different; the unknown tetraploid specie and A.maroccana were in the same group with the high genetic similarity, which was suggested that theunknown tetraploid specie might be A. maroccana; The results showed that the genetic relationship among accessions of hexaploid species was associated with the sources of the accessions according toUPGMA clustering. This study revealed the genetic relationship of the35accessions of oats andprovided useful references for the classification and evolutionary studies of oats.3. The three primers AM63, AM447and AM1403selected from26SSR primers with a clearpolymorphic bands were used to distinguish between3different ploidies of oats. The bands producedfrom the three primers were converted into SSR fingerprint, which can be used to identify differentploidies of oats, and will be of importance in characterizing oat germplasm of different ploidy species. |
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