Evaluation Of Aegilops Umbellulata And Its Derived Germplasm

Aegilops umbellulata（2n=2x=14,UU）is a wild relative of wheat,harboring genes related to several disease resistance,stress tolerance and quality.Thus,it has potential use in the genetic improvement of wheat.The chromosomes numbers of triploid F₁ hybrids of Triticum turgidum with Ae.umbellulata can be naturally doubled via unreduced gametes to generate amphidiploids,which can serve as an important bridge material to transfer beneficial genes/traits from Ae.umbellulata into wheat.Therefore,evaluation the genetic resources of Ae.umbellulata,elucidating the cytological mechanism of the formation of synthesized amphidiploids in T.turgidum-Ae.umbellulata triploid F₁hybrids and exploring the excellent characters of T.turgidum-Ae.umbellulata amphidiploids will contribute to the comprehensive understanding of the beneficial genes/traits of Ae.umbellulata.Consequently,this study will provide a genetic basis for the transfer and utilization of these useful genes/traits.In the present studies,we focus on the evaluation and utilization of Ae.umbellulata genetic resources.Firstly,to study the genetic diversity and chromosomes variation,the fluorescence in situ hybridization（FISH）karyotypes of Ae.umbellulata and materials used as controls,including Ae.uniaristata,Ae.comosa,and Ae.markgrifii,were established using repetitive sequences.Secondly,the stripe rust resistance,heading date,and the contents of iron,zinc,and seed gluten proteins of Ae.umbellulata accessions were investigated.We also obtained triploid F₁ hybrids via distant hybridization between Ae.umbellulata and T.turgidum.Subsequently,amphidiploids were generated through unreduced gametes.In order to understand the genetic effects of U,C,M,and D genome introgression into tetraploid wheat backgrounds,we also investigated and compared the major agronomic and quality traits,as well as the stripe rust resistance of the four synthetic hexaploid species of T.turgidum-Ae.umbellulata（2n=6x=42,AABBUU）,T.turgidum-Ae.comosa（2n=6x=42,AABBMM）,T.turgidum-Ae.markgrifii（2n=6x=42,AABBCC）,and T.turgidum-Ae.tauschii（2n=6x=42,AABBDD）.The main results are as follows:1.Comparison the FISH Karyotypes of Ae.umbellulata with diploid Aegilops species with D,M,and C genomes.The standard FISH karyotypes of Ae.umbellulata,Ae.markgrafii,Ae.comosa,and Ae.uniaristata were established by the FISH probes oligo-p Sc119.2,oligo-p Ta71,oligo-p Ta713,（AAC）₅,（ACT）₇,and（CTT）₁₂,and the combination of probes oligo-p Sc119.2/oligo-p Ta71 plus one of the following probes（AAC）₅,（ACT）₇,（CTT）₁₂,were identified as suitable probes to clearly distinguish the seven pairs of chromosomes of Ae.umbellulata,Ae.markgrafii,Ae.comosa,and Ae.uniaristata.Abundant intra-and interspecific genetic variation were discovered in Ae.umbellulata,Ae.markgrafii,and Ae.comosa,but not Ae.uniaristata.The 7U chromosome of Ae.umbellulata had more variants（six variants）than the other six U chromosomes（2-3 variants）.At least five variants were found in every chromosome of Ae.markgrafii and Ae.comosa,and up to 18,10,and 15variants were identified for the chromosomes 2C of Ae.markgrafii,4M of Ae.comosa subsp.comosa,and 6M of Ae.comosa subsp.subventricosa,respectively.Twelve Ae.comosa and 24 Ae.markgrafii accessions showed heteromorphism in homologous chromosomes.One chromosome translocation between the short chromosome arms of 1M and 7M of Ae.comosa PI 551038 was identified.The diversity and variation of FISH karyotypes among Ae.umbellulata,Ae.markgrafii,and Ae.comosa suggested that these three species may undergo a large number of chromosomal rearrangements in the evolutionary process.The FISH karyotypes can be used to clearly identify the chromosome variations of each chromosome in these Aegilops species and also provide valuable information for understanding the evolutionary relationships and structural genomic variation among Aegilops species.2.Investigation the stripe rust resistance,heading date and main quality traits of Ae.umbellulataThe stripe rust resistance of 46 Ae.umbellulata accessions were investigated in four environments,of which 42 accessions were classified as resistant,while the other four accessions were classified as susceptible to the stripe rust.The average heading days of Ae.umbellulata was significantly longer than that of three common wheat cultivars（181.8±10.5 vs.137.0±4.3 days）,with the exception of PI 226500（138.9±4.6 days）.The Ae.umbellulata accessions also showed high variability in Fe（69.74-348.09 mg/Kg）and Zn（49.83-101.65 mg/Kg）contents.Three accessions（viz.PI 542362,PI 542363,and PI554399）showed relatively higher Fe（230.96-348.09 mg/Kg）and Zn（92.46-101.65 mg/Kg）contents than the others.The gluten proteins of Ae.umbellulata and the control species were separated by reversed-phase high-performance liquid chromatography（RP-HPLC）.Ae.umbellulata had the highest proportion of HMW-GS/glutenin（Ae.umbellulata vs.other species=mean:28.70%vs.18.63%;range:17.06%-38.35%vs.15.56%-25.43%）and HMW-GS/LMW-GS（Ae.umbellulata vs.other species=mean:0.41 vs.0.24;range:0.21-0.62 vs.0.19-0.35）,the unique elution peaks in all the gluten proteins were detected,especially in low-molecular-weight glutenins（LMW-GS）andγ-gliadins at elution times of41-42 min and～57 min,respectively,in comparison with other species.Furthermore,Ae.umbellulata had the highest proportion ofγ-gliadin among all the species investigated（Ae.umbellulata vs.other species=mean:72.11%vs.49.37%;range:55.33-86.99%vs.29.60-67.91%）.These results demonstrated that Ae.umbellulata exhibits great diversity in the investigated traits,providing a potential gene pool for the genetic improvement of these traits in wheat.3.Genetic behavior of T.turgidum-Ae.umbellulata hybridsWe produced a total of 11 T.turgidum-Ae.umbellulata triploid F₁ hybrids,by wide cross of Ae.umbellulata with T.turgidum ssp,designated as STU 2 and STU 7-STU 16.All the triploid F₁ hybrids had 21 chromosomes,and the chromosome numbers of F₂ were varied from 35 to 43 among crosses.The frequency of euploid and aeuploid of F₂ were49.6%and 50.4%,respectively.In the partial amphidiploids,the U chromosomes was most likely lost（26.8%）among the three chromosome groups of A,B,and U,followed by B（22.8%）,and A chromsomes（11.8%）.Three types of chromosome translocation were found in F₂.Polymorphic FISH karyotypes were identified in all the U chromosomes.There are two mechanisms of the formation of the unreduced gametes in T.turgidum-Ae.umbellulata triploid F₁ hybrids,that is first division restitution（FDR）and single-division meiosis（SDM）.The FDR was occurred in five T.turgidum-Ae.umbellulata triploid F₁hybrids,and both FDR and SDM were discovered in the remaining six crosses.During the meiosis of T.turgidum-Ae.umbellulata F₁hybrids,some abnormal chromosome phenomenon was also observed,such as lagging chromosomes,chromosome bridges,micronucleus and multipolar division in telophase.Pearson correlation coefficients among selfed seed-seeting rate,the number of univalent and bivalent,and the average number of chiasmatas has showed that the self-seed setting rate of the T.turgidum-Ae.umbellulata triploid F₁hybrids was significantly positive correlated with univalents（r=0.722^*,P<0.05）and was significantly negative correlated with rod bivalents（r=-0.684^*,P<0.05）and the average number of chiasmata(r=-0.740^**,P<0.01).Morphological traits of 11 T.turgidum-Ae.umbellulata triploid F₁ hybrids were investigated.The plant height and the number of spikelets of triploid F₁ hybrids were intermediated between both parents.The spike lengths of all triploid F₁ hybrids except for STU 7,were significantly higher than the diploid Ae.umbellulata parents,but significantly lower than the tetraploid wheat parents.Further,the number of tillers among triploid F₁ hybrids was differed from each other and was determined by their female parents.For example,the triploid F₁ hybrids using T.turgidum ssp.dicoccum PI 94668 as female parents had more tiller numbers than the tetraploid wheat parents,but the hybrids using T.turgidum ssp.durum Langdon as female parents except for STU 14,had simliar tiller numbers to the tetraploid wheat parents,and they had less tiller numbers than the diploid Ae.umbellulata parents irrespective to their female parents.4.Analysis of the major agronomic and quality traits of T.turgidum-Ae.umbellulataThe major agronomic and quality traits of four amphidiploids between T.turgidum ssp.and diploid Aegilops species,including T.turgidum-Ae.umbellulata（2n=6x=42,AABBUU,STU）,T.turgidum-Ae.tauschii（2n=6x=42,AABBDD,STD）,T.turgidum-Ae.markgrifii（2n=6x=42,AABBCC,STC）,and T.turgidum-Ae.comosa（2n=6x=42,AABBMM,STM）were investigated.There are huge differences in the investigated traits among STU and other three amphidiploids.The plant height,spike length,awn length,spikelet numbers,and the tiller numbers of STU were between tetraploid wheat and Ae.umbellulata parents but very close to the tetraploid wheat parents.The plant height of STU was significantly lower than that of STC and STD.The grain length,width,and weight of STU were larger than those of their parents.The stripe rust resistance of STU was derived from Ae.umbellulata.It was found that all of the synthetic hexaploid species including the STU inherited the HMW-GS,LMW-GS,and gliadins from their both parents.The ratios of HMW-GS/glutenin,HMW-GS/LMW-GS,andγ-gliadin/gliadin in STU were simliar to those of STM,but significantly higher than those of STC and STD.STU had high zinc content and its zinc content also simliar to STC,but higher than that of STM and STD.The iron content in STU were simliar to those of STD,but significantly lower than those of STC and STM.The results suggested that the agronomic and quality traits of four T.turgidum-Aegilops amphidiploids were very different,and can serve as potential gene pools for the genetic improvement of wheat related to thses traits.