| Aegilops tauschii is the D-genome progenitor of wheat, as one of wheat wild relatives, it possesses a wide range of resistance to biotic/abiotic factors and could be precious resources for wheat improvement. Ae. tauschii is clearly different from common wheat in morphological traits, and there is more abundant genetic diversity among Ae. tauschii, also, Ae. tauschii is the secondary gene pool of hexaploid wheat, thus, it can be used to broaden the genetic basis of wheat, the research of genetic diversity of morphological traits will help to utilize the species. Phosphorus deficiency is one of the main limiting factors to wheat production, to solve this problem, because of the limited genetic variation in common wheat, researchers focused on Ae. tauschii. However, there is few people did screen job for phosphorus deficiency tolerance, the good genes in Ae. tauschii remain to excavate. In this paper, we evaluated 29 morphological traits that investigated in years 2012 and 2013 in field, conducted large-scale screening for tolerant Ae. tauschii to phosphorus deficiency using hydroponic experiment. Additionally, using 10K single nucleotide polymorphism (SNP) chips which covering the whole genome of Ae. tauschii, we did marker-trait associations and finally identified a few significant SNPs that associated with morphological traits and phosphorus deficiency tolerance related traits. What’s more, we proposed a lot of putative candidate genes by searching of public databases. The main results are described as follows:1. A total of 29 morphological traits were investigated in the field in a natural population of 322 Ae. tauschii accessions. Analysis of variance revealed significant variation among accessions for all morphological traits. Broad-sense heritability estimates showed that GW1 and GW2 had the highest heritability (0.94) and LN had the lowest heritability (0.27). Pearson correlations of the same traits between years 2012 and 2013 indicated that all investigated morphological traits were significantly correlated (P<0.01) between the two years. The traits GW1 and GW2 are highly positive correlated (r=0.989**, P<0.01), the traits AL2, SPW, GT1, GT2, LW1, LW2, PL2, PW1 and PW2 was shown to be significant correlated (P<0.05)with all other traits, respectively. Discriminant function analysis indicate that 291 out of 322 accessions were classified in keeping with division results by genotypes. Cluster analysis showed that all accessions could be divided into four groups. These suggested that accessions grouping were not conforming by geographical distribution.2. By using 7185 SNPs, we also did GWAS of 29 morphological traits. The results showed that by using a GLM, we identified 12444 significant SNPs, and a MLM revealed 28 significant SNPs, these SNPs explained 2.04% to 9.35% of phenotypic variation. Both models detected 15 significant SNPs which distributed on the 6 chromosomes ofAe. tauschii except 1D, these SNPs associated with 10 morphological traits.3. Use of public databases, we identified 21 putative candidate/flanking genes related to morphological traits. These identified genes including various enzymes genes, hormone responses genes, regulatory elements genes and transposable elements genes. This work provides a fundamental resource for Ae. tauschii genetics research, also, it is useful for further dissecting genetic mechanism of morphological traits in Ae. tauschii and wheat.4. A total of 380 Ae. tauschii genotypes were used to evaluate their phosphorus deficiency tolerance under applied phosphorus and non-applied phosphorus conditions at seedling stage. Analysis of variance revealed obvious variation among genotypes for all tested traits. Heritability estimates showed that root dry weight (RDW), shoot dry weight (SDW), total dry weight (TDW) is highly inheritable. Principal component (PC) analysis showed that first four PCs explained 81.387%of total variation. S value and phosphorus deficiency tolerance index (PDTI) showed that all Ae. tauschii genotypes can be divided into three groups, high (17%), moderate (58%) and low (25%) tolerance groups. Compared with other cultivated wheat using S value and PDTI, the top five tolerant Ae. tauschii genotypes have stronger ability of phosphorus deficiency tolerance than other cultivated wheat. The top five tolerant Ae. tauschii genotypes have relative higher tolerance than other wheat, and can be further used for wheat genetic improvement and molecular breeding for abiotic stress tolerance.5. By using 7185 SNPs genotyped in a core collection of 380 natural Ae. tauschii accessions, we did genome-wide association study (GWAS) of phosphorus-deficiency-tolerant traits. The results showed that by using a general linear model (GLM), we identified 149 significant SNPs, and a mixed linear model (MLM) revealed 40 significant SNPs, these SNPs explained 4.183% to 8.265% of phenotypic variation. Both models detected 25 significant SNPs which distributed on the 7 chromosomes of Ae. tauschii, these SNPs associated with 6 phosphorus-deficiency-tolerant traits.6. Searches of public databases revealed 26 putative candidate/flanking genes related to phosphorus-deficiency tolerance. These genes were grouped in six categories by the types of proteins they encoded:defense response proteins, enzymes, promoters and transcription factors, storage proteins, response to vernalization or proteins triggered by phosphorus deficiency. |
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