Identification Resistance Gene Analogues And Development Of RGAs Genetic Markers In Triticum Dicoccoides

Wild emmer wheat (Triticum dicoccoides, 2n=4x=28, AABB), the progenitor of tetraploid and hexaploid wheat, was resistant to stripe rust, leaf rust and powdery mildew, and salt tolerance, and had higher genetic diversity. The resistance gene analogs (RGAs) from wild emmer wheat accessions were amplified by using specific degenerated primers based on the conserved regions of nucleotide binding site - leucine rich repeat (NBS-LRR) domain of plant resistance genes (R genes) in this study. Then RGA markers were developed and used to evaluate the genetic diversity of 138 accessions wild emmer wheat. The results were described as follows:1. A total of 27 RGAs were isolated from 20 Triticum dicoccoides accessions by using 8 pairs of specific degenerated primers based on the conserved regions of nucleotide binding NBS-LRR domain of plant R genes. The identity of DNA and amino acid sequences between the 27 RGAs ranged from 22.5% to 99.9% and from 6.1% to 99.6%, respectively. The 27 RGAs were classed into 4 groups with MEGA3.1.2. Twenty-nine sets of specific PCR primers were designed based on 27 RGAs sequencesand cloned R genes sequences. Based on the data of 29 primer pairs amplified, genetic diversity of 138 Triticum dicoccoides accessions was evaluated. Five out of 29 specific PCR primers had not target bands, while between the targets bands amplified by 14 specific PCR primers were different. Fourteen sets of specific primers were used to assess the genetic diversity in 15 Triticum dicoccoides populations and the correlation between specific primers and ecological factors. The He and Shannon's information index among 15 populations varied from 0.060 to 0.290 and 0.087 to 0.440, with a mean of 0.195 and 0.295, respectively. The range of polymorphic per population (P) was 0.143 to 0.857. The mean value of D (0.001 to 0.252) was 0.087. It was also proved that genetic differentiation between populations was independent of geographical distances between the sites of collection by Mantel test (r = 0.382, p = 0.9995). A neighbor-joining tree based on the genetic distance showed 15 populations were irregularly divided into 4 families. The analysis spearman rank correlations (r_s) between genetic diversity and environment factor showed, the He was positively correlated with latitude (Lt) (r_s = 0.559, p=0.03), while the P and Shannon's information index didn't significantly correlate with any ecological factors. A total of 37 significant (p < 0.05) correlations were obtained between the specific RGAs markers and 20 climate factors using Spearman rank correlation analysis. So the genetic diversity of wild emmer wheat was related to the ecological factors of the origin area.