Seed dormancy and factors controlling dormancy breakdown in buffel grass accessions from contrasting provenances.
Seed dormancy and factors affecting dormancy breakdown were studied in 15 accessions of Cenchrus ciliaris of near-equatorial origin and 6 of near-tropical origin, and cv. Biloela. Within latitudes of origin, pairs of accessions were from high (1200-1400 mm), medium (700-850 mm), low (400-500 mm) and very low rainfall (25-220 mm) sites. Plants were grown in SE Queensland. Ripe fascicles were subjected to a range of temp. and stratification treatments and germination, dormancy and viability were recorded. Four weeks after harvest, percentage germination was 0-5.5%, and the percentage of dead seeds was 0-18.5% (with an anomalous 34.6% for 1 accession). Treatment of fascicles 4 weeks after harvest at 60°C or alternating 60/25° for 12 weeks significantly increased germination. Germination was higher from equatorial than from near tropical accessions and from high than from low rainfall provenances. Treatment of either dry or moistened fascicles at 4° for 2-8 weeks had little effect on dormancy, but moistening reduced viability. The percentage of dead seeds tended to be lower in equatorial and higher rainfall accessions. High temp. decreased viability, but after 2 weeks of treatment the rate of loss of viability was similar in high and low temp. treatments. Seeds from fascicles with more than 1 seed were more dormant than those from 2-seeded fascicles and had lower germination percentages. Max. percentage germination for an accession was related to the percentage of living seed shortly after harvest, which confounded interpretation of data in terms of dormancy differences. It was concluded that the C. ciliaris accessions differed in dormancy attributes which may be adaptive to their climate of origin.