Molecular Cytogenetic Characterization Of The Derivatives From Wheat-Psathyrostachys Huashanica-Thinopyrum Hybrids

As one of the earliest domesticated crop worldwide, wheat has become predominant because of its wide distribution, high yield and nutrition as well as the role in food trade. Currently the consumption of wheat grain has been increasing and usually more than its production due to the progress in world’s population and the changes in public food constitution. Furthermore, the sustainability of wheat yield has been challenged by global climate change and shrinking arable land and so on. The genetic resources of wheat are fundamental in breeding programs and also act as basic materials for evolutionary and ecological research. On the other hand, a number of materials performing well in yield, grain quality and disease resistance have been utilized widely in the most of breeding programs, leading to the narrow genetic background and diversity, named the’bottle neck’. This problem has cost much and should be solved in the following decades. To achieve this, breeding new cultivars of wheat through the introduction of desirable genes from the related species is a promising strategy. Wheat has rich genetic resources in Triticeae, and the chromosomes or chromosomal fractions related to valuable traits are able to be transferred by wide-cross technique, termed chromosome engineering. As two species in the third class of gene pools, Psathyrostachys huashanica and Thinopyrum intermedium have been used recently. In this study we tried to introduce desirable traits from two species through chromosome engineering. Also, the chromosomal behaviour of P. huashanica and T. intermedium during cell cycles were investigated to enable better understanding of the chromosome transgression.Owing to the low fertility of the hybrids deserved from the cross between wheat and P. huashanica or T. intermedium, two amphiploids, wheat-P. huashanica (AABBDDNsNs,2n=56,"PHW-SA") and wheat-T. intermedium (2n=8x=56, AABBDDEE,"Zhong3"), were utilized as the donors of P. huashanica and T. intermedium chromosomes, respectively.27lines were selected from the F4progeny by sellfing of the F1hybrids. The chromosome constitutions of these lines were subsequently identified using molecular cytogenetic techniques. The results were showed as the following.1. Cytogenetic analysis showed that the chromosome number ranged from42to50and the average number of chromosomes was44.96, satellited chromosomes can be observed in each cell. Univalents were found during meiosis, varying from0.04to4.53. Ring and rod bivalents were16.94-21.18and0.55-3.86. respectively. Multivalents were observed only in five lines. One-third of the lines had42chromosomes and normal chromosome pairing with rare univalents (less than0.13per cell) and multivalents. The others had chromosomes more than42with a few univalents and multivalents. Across all lines, each cell consisted of1.26univalents,21.78bivalents,0.04trivalents and0.03tetravalents.2. Genomic in situ hybridization (GISH) on these27lines revealed that no chromosomes showing signals when the DNA of P. huashanica was used as the probe with the DNA of Chinese Spring (CS) using as the block.1-7chromosomes were labelled when the DNA of T. intermedium was used as the probe. The chromosomes of T. intermedium appeared as the form of univalents in19lines, the ratio was high as70.4%, including the whole ones and translocated chromosomes between wheat and T. intermedium. In eight lines the ring or rob bivalents of T. intermedium were found. Synapsis and pairing between the chromosomes of T. intermedium and wheat took place while some of wheat chromosomes appeared as univalents.3. A lot of Robertsonian translocations and Fractional translocations between wheat and T. intermedium were detected in the F4generation. GISH on the chromosomes during meiosis showed21Fractional translocations were found among the27lines, the frequency was high as77.8%, usually taking place at the end of univalents. Two lines,668-10and682-12, are homozygous translocation lines which are also taking place at the end of the univalents revealed by GISH on the pollen mother cells. These wheat-T intermedium Fractional translocations and homozygous translocation lines can be used as the intermediate materials for genetic improvement to common wheat and enrich the genetic diversity of wheat, which has important potential values in wheat breeding.