ALBERT

Notizen: The two most widely grown bromegrass species in North America are smooth bromegrass, a hay type grass, and meadow bromegrass, a pasture type grass. Hybrid populations between these two species have been developed through hybridization and recurrent selection. The objective of this study was to determine the genetic relatedness of the hybrid bromegrass population S-9073M to its parental populations using random amplified polymorphic DNA (RAPD) markers and to determine genetic variation within and between populations. Individuals from each of the three populations were genotyped at 43 polymorphic RAPD loci. One of the RAPD fragments was meadow bromegrass-specific. Cluster analysis showed three groups representing the two parental populations and the hybrid population. An analysis of molecular variance (AMOVA), showed that the hybrid population had the highest within-population variation, followed by meadow bromegrass and smooth bromegrass. The interpopulation genetic distance (phi-statistic =Φst) was highest between meadow and smooth bromegrass and lowest between smooth and hybrid bromegrass. The hybrid population was genetically intermediate to smooth bromegrass and meadow bromegrass, but closer to smooth bromegrass, possibly reflecting the selection criteria used in the development of this hybrid.

Notizen: Meadow bromegrass is a recently introduced pasture grass in western Canada. Its leafy production and rapid regrowth have made it a major grass species for pasturing beef animals in this region. Because relatively little breeding work has been done on this species, there is little information on its breeding behaviour. The main objective of this study was to estimate genetic parameters and assess breeding methodologies for meadow bromegrass. Forty half-sib (polycross and open-pollinated) and full-sib (selfed) progenies were evaluated for dry matter and seed yield, fertility index, harvest index, plant height, plant spread, crude protein, neutral detergent fibre and acid detergent fibre. Genetic variation for seed yield, harvest index, and plant height was significant in the open-pollinated and selfed tests. Genetic variation estimates for dry matter yield were negative (polycross), not significant (open-pollinated), or significant (selfed). Estimates of genetic variation for quality traits were not significant, except for acid detergent fibre (selfed). Correlations among characters indicated that it is possible to simultaneously improve seed and forage yield. Rankings of progenies by the half-sib tests for forage and seed yield were not altered by the use of the synthetic parental value (SVi), which includes information from selfed progeny. The polycross progeny test did not discriminate parents as well as the open-pollinated and selfed tests; this may have been a result of non-random pollination in the polycross. Correlation among the progeny tests, showed that open-pollinated and selfed progeny tests agreed for all characters, except for harvest index, while correlation between polycross and selfed tests were significant for six characters but not dry matter yield, and acid and neutral detergent fibres. The most dissimilar tests were polycross and open-pollinated, with significant correlations found only for fertility index, height, spread and neutral detergent fibre. It was concluded that there was significant variation and moderate heritability for most traits in the meadow bromegrass populations evaluated, and that the open-pollinated progeny test is the method of choice for selecting parents for synthetics of this species.