Characterization of Eb genome chromosomes in F3 progenies of new potential secondary Tritipyrum introgressed genotypes by genomic DNA in situ hybridization technique

Primary Tritipyrum is a new synthetic allohexaploid amphiploid cereal which has been developed by crossing the durum wheat (Triticum durum, AABB, 2n=4x=28) and wild brackish grass (Thinopyrum bessarabicum, EbEb, 2n=2x=14). Although primary Tritipyrum lines are tolerant to salt stress but have few undesirable agronomic traits such as brittle rachis and late maturity. To overcome these problems, the new potential secondary introgressed Tritipyrum genotypes were developed from crossing the primary Tritipyrum (St/b) or combined primary Tritipyrum (Ka/b)(Cr/b) lines [AABBEbEb, 2n=6x=42] and bread wheat (Triticum aestivum:AABBDD, 2n=6x=42) cv. Omid and cv. Navid in which the various D chromosomes of bread wheat will probably be substituted with different Eb chromosomes of Tritipyrums. Identification of Eb chromosomes in chromosomal mitotic preparations of new potential secondary Tritipyrum genotypes including F3 progenies of (Omid × St/b) and [Navid × (Ka/b)(Cr/b)] by genomic DNA in situ hybridization (GISH) technique, using indirect labeling for genomic St DNA with Biotin-11-dutp as probe, was carried out. Results showed that using St genomic DNA instead of genomic DNA of Eb genome as probe made less St cross hybridization with A, B, D chromosomes and high differentiation between Eb chromosomes with A, B and D genomes chromosomes. This indicated that in spite of high genetic similarity between Eb and St (Pseudoroegneria stipifolia, StSt, 2n=2x=14) genomes, the St genomic probe is recomended for identification of Eb chromosome, because genetic similarity of St genome with A, B and D genomes is less than Eb genome with these three genomes of bread wheat. A range of 1-6 Eb chromosomes in mitotic chromosomal spreads of [Omid × St/b] and [Navid × (Ka/b)(Cr/b)] F3 progenies were detectable which indicated that producing new potential secondary Tritipyrum introgressed genotypes (NPSTIGs) with specific substituted Eb chromosomes with D chromosome was feasible. Therefore, GISH can be used as a powerful selection tool in chromosome engineering of intergeneric hybridization progenies of primary Tritipyrum lines and bread wheat cultivars combinations for selecting the favourable 42 chromosomal constitution genotypes of Eb, A, B and D as a new substituted or recombinant chromosome(s) lines.