Development of a dwarf oat (Avena sativa L.) for northern growing conditions may further improve many important agronomic features of the oat crop including lodging resistance, yield stability, yield potential, grain-straw ratio, and fertile tillering. Our objective in this study was to assess the performance of a Minnesota-adapted dwarf line at high latitudes, through measurement of several traits that characterize duration of pre- and post-anthesis growth and plant stand structure, with special reference to tiller growth and tiller productivity. Response of the dwarf line to seeding rate (250, 500, and 750 viable seeds m(-2)) and nitrogen fertilizer application rates (80, 120, and 160 kg N ha(-1)) was compared with that of a semi-dwarf line, a conventional height cultivar, and a landrace cultivar, all of which are adapted to long-day conditions. The experiments were conducted in Finland (60 degrees 13'N) in 1993 and 1994. The dwarf line produced less grain (less than or equal to 30%) than the other lines but out-yielded the lodging-sensitive landrace in 1994 at a high seeding rate and high rate of nitrogen fertilizer application. As for the semi-dwarf line and conventional height line, the dwarf line produced the highest grain yield at 500 seeds m(-2) which is the standard planting density for oat in Finland. The particularly short duration of the generative phase and associated low number of grains per main shoot panicle are likely to be principal contributors to low mean panicle-filling rate, panicle weight, and grain yield of the dwarf line. However it was better able to tiller and produce head-bearing tillers than the other lines. This increased number of tillers was, however, unable to compensate for yield reduction resulting from low yield potential of the main shoot.
