Synthetic Hybrids of Agropyron dasystachyum x Elymus glaucus and Sitanion hystrix

Ten unemasculated Agropyron dasystachyum spikes exposed to Elymus glaucus pollen yielded 95 hybrid seeds, of which more than half were viable. The hybrids were morphologically variable and included caespitose and highly rhizomatous plants. The A. dasystachyum and E. glaucus parents were tetraploid (2n = 28) and behaved meiotically as alloploids. Chromosome associations in 10 of their hybrids averaged 0.31 I, 13.82 II, and 0.01 III in 525 metaphase-I cells. Subsequent meiotic stages were basically regular; yet no hybrid produced more than 30% stainable pollen. The hybrids were partially fertile and yielded up to 250 seeds under open pollination. Forty-seven viable hybrid seeds developed in 120 emasculated A. dasystachyum florets pollinated by Sitanion hystrix, and the reciprocal cross yielded four viable seeds from 48 florets. These hybrids and their reciprocals were vegetatively uniform and intermediate between the parent species. An apparent reciprocal difference was noted in awn development. Both parents were tetraploid and regularly formed 14 bivalents at metaphase I. Almost 90% of the 259 metaphase-I cells of six A. dasystachyum x S. hystrix hybrids and four reciprocals also contained 14 bivalents. Mean chromosome associations of 0.21 I, 13.88 II, and 0.01 III were observed in these hybrids. Stainable pollen ranged from less than 1% to 8% in the A. dasystachyum x S. hystrix hybrids, and none produced more than nine seeds. Ready cross-compatibility and almost complete genome homologies verify the previously suspected genetic and phylogenetic relations among A. dasystachyum, E. glaucus, and S. hystrix. These three species, as well as many other closely related Agropyron, Elymus, and Sitanion species, belong in the same genus.