Intergeneric Hybrids and Amphiploids between Pseudoroegneria spicata and Critesion violaceum

Abstract

Diploid (2n = 14) Pseudoroegneria spicata ssp. inermis (genome formula, SS; formerly in Agropyron) was hybridized with diploid (2n = 14) Critesion violaceum (genome formula, HH; formerly in Hordeum). The hybrids (genome formula, SH) were morphologically intermediate to the parents. Mean chromosome associations of 7.28I, 3.11II, 0.16III, and 0.05IV were observed at metaphase I in 208 cells from four hybrids. Of the bivalents, 90% were rod configurations leading to a mean chiasma per arm of 0.269. The hybrids were completely sterile. The SSHH amphiploid derivatives were morphologically like the FI hybrids and were partially fertile, averaging 2.6 seeds per spike. At metaphase I, the amphiploids averaged 4.01I, 11.37II, 0.26III, 0.09IV, and 0.03V in 160 cells. Many progeny of the amphiploids were natural outcrosses to other species growing in the same field nursery. At least nine outcross hybrids occurred with Agropyron cristatum (2n = 14; genome formula, PP) and even more with Critesion brevisubulatum (2n = 28; genome formula, HHHH). These two hybrid combinations, whose identities were established on morphological and cytological grounds, were also analyzed at metaphase I. Data from hybrids, C0 and C1 amphiploids, and outcross hybrids led to the conclusions that (1) the S, H, and P genomes are distinctly different but contain some residual homologies, and (2) SSHH amphiploids are segmental alloploids.