Study of old and modern wheat cultivars responses to nitrogen and plant density in Ardabil Region

Old wheat varieties are regarded as useful genetic resources to transfer desirable genes in breeding programs especially in arid zones. On the other hand, modern cultivars have better responses to the inputs application increases, but there have been contradictory reports about the relative advantage of old varieties for cultivation on poor soils. The experiment was carried out in Agricultural Research Station of Islamic Azad University of Ardabil, Iran in 2008-09 to study the responses of old and modern bread wheat cultivars to different nitrogen (N) levels and seeding rate. A factorial split-plot experiment based on a Randomized Complete Blocks Design (RCBD) with three replications was used. The combinations of N levels (54 and 108 kg N.ha-1) with two seeding rates (250 and 400 seeds.m-2) were regarded as main plots and 44 cultivars (15 modern and 29 old bread wheat cultivars) as sub-plots. The results showed that new cultivars produced significantly (P<0.01) greater grain yield than old cultivars (527.18 and 449.41 g.m-2, respectively). The increase was only observed in grain yield, and straw yield was not affected by cultivar. Consequently, Harvest Index (HI) of modern cultivars (0.35) was 13% greater than that of old cultivars (0.31). Modern cultivars had 12% less spikes.m-2 and 26% more grains.spike-1 than old cultivars, but the single grain weights of modern and old cultivars were not significantly different. The cultivars did not have significant differences regarding total tiller number while fertile tiller number was significantly lower in new cultivars (2.30) than in old cultivars (2.57). The decrease in plant height of modern cultivars compared to old ones (11.23 cm) was due to the decrease in internode length (by 2.8 cm.internode-1) and not the node number.