Meiotic behaviour in natural diploid, tetraploid, and commercial diploid crested wheatgrass

Chiasma frequencies and chromosome associations at diakinesis and first metaphase (MI) were studied in natural and commercial diploid Agropyron cristatum and natural tetraploid Agropyron desertorum crested wheatgrass plants. The frequencies of bivalents were 6.988 and 6.980 at diakinesis and 6.980 and 6.976 at MI in the natural and commercial diploids, respectively. The frequencies of bivalents and quadrivalents in the natural tetraploid were 7.728 and 3.072 at diakinesis, and their frequencies at MI were 7.880 and 2.984, respectively. A few univalents were formed at diakinesis and MI in the three crested wheatgrasses, and these were generally associated with trivalents at the two stages in the tetraploid. There were positive and significant correlations between the frequencies of chiasmata at diakinesis and those of chiasmata at MI in the three crested wheatgrasses. Tetraploid A. desertorum, in particular, is thought to be an important breeding material for future studies when growth performance and meiotic regularity are taken into consideration.