No abstract

This research was carried out in a high altitude, cool and short-season environment in the years 2004 and 2005. In this research, the 2-rowed spring barley (Hordeum vulgare) cultivar 'Tokak 157/37' and 18 artificial mutated lines obtained from this cultivar by gamma irradiation were used. The durations for the vegetative period, grain-filling period, and maturity period and their associated growing degree-days (GDD) were studied. The relationships between these phenological growth traits and grain yield were determined and the desirable genotypes which were both early maturing and high yielding were identified. Grain yield was generally higher in the genotypes which had a shortmaturity period and fewer associated GDD, and therefore, negative relationships between grain yield and the phenological growth traits were observed. ML 17 and ML 19 mutated genotypes were found to be both early maturing and high yielding whereas ML 4, ML 12, ML 16, ML 32, ML 34, and ML 36 were only high yielding when compared with the standard cultivar. In environments with cool and limited growing seasons, such early maturing and high yielding genotypes provide the most promising materials from which to develop new cultivars of spring barley.

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.

Chromosome associations and chiasma frequencies at first metaphase (MI) were studied in allotetraploid reciprocal hybrids between perennial ryegrass (Lolium perenne, Lp) and Italian ryegrass (L. multiflorum, Lm), and parent autotetraploid perennial ryegrass. Preferential chromosome pairings were assessed in Lp x Lm and Lm x Lp hybrids. The reciprocal hybrids were found to have significantly higher frequencies of bivalent pairing and lower frequencies of quadrivalent pairing and chiasmata. The mean frequencies of total bivalents at MI were 6.820, 9.885 and 10.040 and total quadrivalent frequencies were 3.320, 1.775 and 1.760 in the autotetraploid parent and the Lp x Lm and Lm x Lp hybrids, respectively. The frequencies of chiasmata were 25.075, 23.455 and 23.315 in the parent and the Lp × Lm and Lm × Lp hybrids, respectively. The frequencies of preferential chromosome pairing in the Lp × Lm and Lm × Lp hybrids were 42.69 and 44.85%, respectively and the results indicate a significant degree of preferential bivalent association in the hybrids. An inverse relationship was found between the frequency of total bivalent and quadrivalent associations in the parent and the Lp x Lm and Lm x Lp hybrids. These reciprocal hybrids are potentially important breeding materials for developing new hybrid cultivars.