Abstract:

The basic genome of Agropyron spp. distributed in the cold and temperate plateau and sands of the Eurasia is the P genome. These species are not only adapted to abiotic stresses, such as drought, low temperature, and barren soils, but also resistant to powdery mildew, Barley dwarf virus, and the rusts in wheat. Moreover, Agropyron species produce multiple tillers, spikelets, and florets. The P genome of Agropyron can be a source of desirable genes for wheat improvement. In the 1990s, cross between wheat and Agropyron species was made, resulting in the development of a number of wheat-Agropyron chromosome addition lines, which made possible to transfer genes from the P genome into wheat by producing chromosome translocations between wheat and Agropyron.
The gametocidal chromosome of Aegilops speicies, which is added to wheat genome, is able to induce various structural variations of chromosomes. Compared to the methods for inducing chromosome variations, such as irradiation, tissue culture and Ph mutant, gametocidal method is highly effective in inducing chromosome variations between wheat and relative species. This method has been used to produce chromosome translocations between wheat and Haynaldia villosa, Leymus racemosus, Elytrigia elongate, and Secale cereale, with a frequency of over 10%. However, no study has been reported on producing wheat-Agropyron chromosome translocation using gametocidal method.
In the present study, eight wheat-Agropyron cristatum addition lines were crossed with Chinese Spring-Aegilops cylindrica (2C) addition lines and their morphological and cytological performances were investigated. The objective of this study was to lay a foundation on developing wheat-Agropyron chromosome translocations by inducing chromosome variations between wheat ABD genomes and Agropyron P genomes with gametocidal chromosome. The results showed that the chromosome addition lines Ⅱ-4-2, Ⅱ-21-6, Ⅱ-21-2, and Ⅱ-11-1 had transmission rate of 100%. The transmission rate was high in lines Ⅱ-5-1 and Ⅱ-9-3, but low in lines Ⅱ-29-2 and Ⅱ-5038. Chromosome abnormality was observed in F₁ plants during meiosis. The frequency of pollen mother cells with over 3 univalents was 35.3%. Micronuclei were observed in 74% of tetrads, and chromosome fragments and bridges appeared in 20.3% and 23.8% of cells. In certain crosses multivalents, multifid quadrants, and retrogression were observed. These aberrations of chromosome behaviors indicated that the gametocidal chromosome was effective during the formation of gametes. The percentage of seed setting in F₁ plants varied from 51.67% to 71.37%, indicating that the gametocidal chromosome 2C had a different effect on various wheat-Agropyron chromosome addition lines.

Key words: Wheat (Triticum aestivum L.), Wheatgrass (Agropyron cristatum Gaertn.), Gametocidal chromosome, Disomic addition line, Cytology