P. Mikó1, 2, M. Megyeri2, M. Molnár-Láng2
1Agricultural Institute, MTA Centre for Agricultural Research, Martonvásár, Hungary 2Plant Genetics and Biotechnology Programme, Plant Science PhD
School, Szent István University, Gödöllő, Hungary
As the negative eff ects of the global climate change are increasing, it is vital to improve the bread wheat (Triticum aestivum L.) breeding lines continually, adorning them with better resistance that can cope with the main biotic and abiotic stresses. One possible way for improving the resistance and adaptability of bread wheat is the utilization of its wild relatives in prebreeding. Most studies on the utilization of the genes responsible for resistance have involved direct crosses between T. aestivum and its wild relatives. However, apart from direct crosses, another possible way of utilization could be the development of new synthetic amphiploid wheat lines. Present study is focusing on the simultaneous utilization of Triticum timopheevii Zhuk. (2n=4x=28, AtAtGG) and Triticum monococcum L. subsp. monococcum (einkorn;
2n=2x=14, AmAm) through their hybrid, because both of them have outstanding
resistance against the main wheat fungal diseases.
Before crossing it is necessary to choose the most suitable lines from these species, in order to gain valuable prebreeding materials. Therefore, detailed characterisation was carried out on all of the 56 T. timopheevii accessions of the Martonvásár Cereal Gene Bank for the main phenotypic and resistance characters. The evaluation of the assessment data revealed that members of the base species and subsp. timopheevii are likely to be more advantageous for wheat breeding than those of the subsp.
armeniacum group. Although the latter have relatively early heading date, they are
more susceptible to fungal and viral diseases, and have a prostrate growth form with lower yielding ability and brittle rachis, which could make their utilization in wheat breeding more diffi cult. Aft er a detailed evaluation of the results, the best 11 accessions from the ssp. timopheevii group were selected for a crossability test with an already prebred, semi-dwarf einkorn line, ‘1T-1’. On the basis of the results one accession (Triticum timopheevii Zhuk. var. rubiginosum, Acc. No.: MVGB845) with the best seed set was selected for the development of the new synthetic amphiploid,
Triticum timococcum. Aft er crossing, the triploid genome (2n=3x=21) of the selected
hybrid seedlings (F1) was doubled by colchicine-treatment (F1 -> C1).
Detailed phenotypic evaluation was carried out under natural and artifi cial growing conditions in 2012 and 2013. Based on the results, T. timococcum has intermediate characteristics in terms of spike (spikelet) shape and plant height, while it is similar to the female parent, T. timopheevii regarding pubescence. Like its parents, T. timococcum showed outstanding resistance to the main fungal diseases of wheat. T. timococcum headed later and developed longer and looser spikes, fewer
tillers and only a third as many seeds than its parents. Beside the fi eld assessment, an additional trial on artifi cial leaf rust infection of seedlings has also proved the high resistance of T. timococcum.
Identifi cation of the hexaploid genome of this synthetic amphiploid using fl uorescent in situ hybridisation (FISH) with repetitive DNA probes has proved normal doubling with 42 chromosomes in most of the plants of the C2 and C3 generations. Detailed identifi cation has revealed that this plant material has 14 chromosomes originated from einkorn, and 28 chromosomes originated from T.
timopheevii. This result was also confi rmed by genomic in situ hybridization (GISH),
which helped to eff ectively distinguish the A and G genomes. Genomic DNA of the S genome was extracted from the diploid Aegilops speltoides Tausch, because this genome is similar to the G genome of T. timopheevii. In the case of A genome, DNA was extracted from Triticum urartu Thumanian ex Gandilyan, the A genome donor of bread wheat, because the A genome of T. timopheevii is mostly similar to that of wheat. The successful discrimination of the chromosomes was supported by the karyotypes of the parental genomes and the successful optimization of the GISH technique for the Am, At and G chromosomes was achieved in the present study.
The simultaneous utilization of T. timopheevii and T. monococcum has continued with the development of hybrids between T. timococcum and T. aestivum ‘Mv9kr1’ (carries the recessive allele of kr1 crossability gene) followed by back-crosses with Mv9kr1 in order to get more useful materials for wheat breeders. A comparative crossing trial proved that crossing with T. timococcum is less eff ective than the direct cross between bread wheat and T. timopheevii. However, using T. timococcum could help in the introduction not only of T. timopheevii-derived, but also of einkorn- derived genes into bread wheat.
Progenies of the fi rst back-cross (BC1) were also examined with FISH and GISH according to the fi ndings of the fl uorescent in situ hybridization of T. timococcum. Beside several G chromosomes, some Am chromosomes were also identifi ed in the
bread wheat genetic background of the BC1 plants showing promising opportunity for the development of diff erent addition lines and/or translocations aft er the further back-crosses. The second back-cross (BC2) was successfully carried out in the beginning of 2014. The progenies will be grown in climate chamber, and their genomes will be examined soon.
Study has also begun on the molecular cytogenetic identifi cation of T. aestivum ‘Mv9kr1’ × T. timopheevii subsp. armeniacum hybrids developed earlier in Martonvásár.
Three backcrosses with Mv9kr1 were carried out on this material at that time. Present study has started to analyse the genome composition of these BC3 lines using improved molecular cytogenetic techniques (FISH, GISH), and some promising results have already been obtained. One of the lines was identifi ed as a disomic addition line, which is carrying the pair of 6G chromosomes of T.
timopheevii, and this line showed outstanding resistance against leaf rust in an
artifi cial inoculation trial carried out on seedlings.
The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/ 2007-2013) under the
Grant Agreement n°245058-Solibam (supplementary Hungarian project EU_ BONUS_12-1-2012-0032), and from two National Science and Technology Offi ce projects (TECH_08-A3/2-2008-0397 – CONFU_08 and TECH_08-A3/2-2008-0423 – ALKOBEER – Hungary).