Intergeneric hybrids between Hordeum vulgare and Elymus trachycaulus resistant to Russian wheat aphid

Abstract

Intergeneric hybrids between cultivated barley (Hordeum vulgare L.) (2n = 2x = 14) and slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), PI 531691 (2n = 4x = 28), were produced. This slender wheatgrass accession carries resistance to Russian wheat aphid, Diuraphis noxia Mordvilko, and was used as pollen parent. The seven hybrid plants were also resistant to Russian wheat aphid. The hybrids were produced at a frequency of 0.21% of emasculated and hand-pollinated florets. Chromosome pairing in all the euploid hybrids was very low (average chiasma frequency per cell, 0.30). This indicates that the I genome from H. vulgare is remotely related to the SH genomes of E. trachycaulus. Expression of resistance to Russian wheat aphid in all the hybrid plants demonstrates that the nuclear gene or genes for insect resistance contributed by E. trachycaulus are either dominant or hemizygous effective. Five of the seven hybrid plants were vigorous and produced well-developed flowering spikes; however, they did not shed viable pollen. Since all the vegetatively cloned plants of these hybrids exhibited a high degree of perennial characteristics and could be induced to flower under a favourable light and temperature regime, they appear congenial for chromosome doubling and backcrossing. Preliminary observations suggest that successful backcrossing could be achieved using the F1 hybrids as pistillate parent and H. vulgare as pollen parent.Key words: Russian wheat aphid resistance, intergeneric hybrids, genomic relationship, chromosome pairing, Hordeum vulgare, Elymus trachycaulus.