THE CHROMOSOME STABILITY OF HORDEUM-VULGARE L H-BULBOSUM L CHROMOSOMESUBSTITUTION PLANTS GROWN AT 2 TEMPERATURES

The perennial wild species Hordeum bulbosum is closely related to cult ivated barley (H. rulgare) and possesses useful traits such as disease resistance. Introgression of desirable genes into barley has recently been achieved by backcrossing fertile triploid hybrids between H. vul gare (2x) and H. bulbosum (4x) to barley. Single and double monosomic chromosome substitution plants were also developed from similar crosse s, but consistent chromosome pairing and stability has been difficult to achieve. Since temperature influences chromosome behaviour in H. vu lgare x H. bulbosum hybrids, the effect of two temperatures (15 and 21 degrees C) on dividing somatic ovary wall cells and pollen mother cel ls was investigated. At 21 degrees C, most of the plants contained hig her proportions of cells with less than the full chromosome complement , indicating elimination of the H. bulbosum monosomes. However, at 21 degrees C, homoelogous chromosome pairing tended to be greater than at 15 degrees C. To promote high chromosome pairing and stability, optim um temperatures should be further determined to enable genetic recombi nation to take place.