MEIOTIC STABILITY OF INTERSUBSPECIFIC HYBRIDS OF SNAKE RIVER X THICKSPIKE WHEATGRASSES

Based on genomic makeup and partial hybrid fertility, Snake River whea tgrass (proposed name Elymus lanceolatus ssp. wawawaiensis) has been r ecognized since 1986 as a subspecies of E. lanceolatus (Scribn. and J. G. Smith) Gould. Thus it is conspecific with thickspike wheatgrass [E. lanceolatus ssp. lanceolatus (Scribn. and J.G. Smith) Gould]. However , these two wheatgrasses display distinct morphological features, phys iological traits, geographical distributions, and habitat preferences. Hybridization of the two subspecies generates valuable germplasm with considerable heterosis, but the hybrids are partially male sterile. O ur objective was to determine the degree and nature of hybrid male ste rility. Mean chromosome pairing (and pollen stainability) was 0.11 I 13.90 II + 0.02 IV (84%) for 'Secar' Snake River wheatgrass and 0.10 I + 13.83 II + 0.01 III + 0.05 IV (78%) for 'Bannock' thickspike wheat grass, the parents in the original cross, 0.60 I + 13.61 II + 0.01 III + 0.04 IV (55%) for three F-1 hybrid populations, and 0.09 I + 13.92 II + 0.01 III + 0.03 IV (80%) and 0.44 I + 13.66 II + 0.01 III + 0.05 IV (64%) for backcross populations to Bannock thickspike wheatgrass an d BBR-syn Snake River wheatgrass, respectively. The low frequency of m ultivalents in the hybrids indicated that male sterility resulted from some degree of genetic incompatibility rather than a major chromosoma l rearrangement. Because hybrid and backcross populations possessed re asonable levels of pollen stainability and chromosome abnormalities we re absent, they should respond readily to selection for high pollen st ainability.