SEED DEVELOPMENT AND SEED YIELD POTENTIAL OF ITALIAN RYEGRASS (LOLIUM-MULTIFLORUM LAM) POPULATIONS

Greenhouse and field experiments were carried out to study the seed de velopment and seed yield potential of three populations of Italian rye grass (Lolium multiflorum Lam.). These included an ecotype (Bb 1276) c ollected in the Lombardy Plain region of northern Italy, cv. Tribune, which was derived from this ecotype, and cv. Lemtal, a widely used cul tivar from Belgium. Artificial seed shedding techniques in the greenho use study showed that Bb 1276 began shedding seed at a higher moisture content than cv. Tribune which in turn was higher than cv. Lemtal. Th e pattern and rate of shedding was similar for all three populations a nd generally Bb 1276 and cv. Tribune gave a greater proportion of shed seed than cv. Lemtal. Although the pattern of decline in seed moistur e content was similar for all three populations, generally cv. Lemtal had a higher moisture content than cv. Tribune with Bb 1276 the lowest . Cultivar Lemtal had the highest mean 1000 seed weight, and Bb 1276 t he lowest, with cv. Tribune intermediate. The field study involving cv . Tribune and cv. Lemtal showed that with the exception of 1000 seed w eight, which for cv. Tribune was some 6% lower than that of cv. Lemtal , all the seed yield components were similar. Seed yields taken every 3 days after the standing crop had reached 50% moisture content showed that both cultivars increased in yield until harvest 3. After this da te the seed yield of cv. Lemtal remained stable up to harvest 5 while that of cv. Tribune declined. The maximum seed yield of cv. Tribune wa s achieved at a seed moisture content of 42-9% while that of cv. Lemta l remained stable from 42-3% to 37.5%. The seed moisture content of th e two cultivars again showed a similar pattern of decline but it was n ot possible to show consistent differences between cv. Lemtal and cv. Tribune. The 1000 seed weight of cv. Tribune was lower than that of cv . Lemtal, and the maximum seed weight of cv. Tribune appeared to be ac hieved earlier. Germination counts taken after harvest showed both pop ulations exhibiting a high level of post-harvest dormancy. Later count s taken 3 months after harvest were significantly higher than those ta ken earlier and there were no differences between cultivars or harvest s. The results are discussed in relation to the potential for selectin g for improved seed yield potential in Lolium multiflorum Lam. populat ions from northern Italy and suggestions are made for maximizing the h arvested seed yield of cv. Tribune.