abstract
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Better crop management and the use of higher yielding cultivars led to a noteworthy increase in worldwide wheat yields. In Uruguay, wheat (Triticum aestivum L.) is an important crop planted either as double purpose crop (forage and grain) in mixed farming systems or only for grain purposes. In recent years, average production under no-till management ranged between 2.1 to 3.6 t ha-1, highly depending on precipitation and disease epidemics. In 2015, 330.000 ha were seeded with wheat. In the present study, thirty-four wheat cultivars released in 23 different years between 1918 and 2017 in Uruguay were evaluated for 3 years (2012, 2013 and 2018) at La Estanzuela, the experimental station of the national agricultural research institute, assessing the genetic improvement in agronomic and qualitative components. Wheat was planted between May and June with a sowing density of 294 seeds m-2 and harvested in December. Experimental plots measured 8.0 m x 2.1 m; in each one, two sheaves (0.76m2) were harvested. All plots received a basal fertilizer application of nitrogen (N) and phosphorous (P) and two N broadcast fertilizer applications at Z 22 and Z 30. Total applied fertilizer averaged 40 kg P2O5 ha -1 and 120 kg N ha-1. Grain yield incremented continuously by breeding progress and doubled in cultivars released after 2009 compared to average yields of the oldest cultivar from 1918. The ratio of harvested grain to total shoot dry matter (harvest index, HI) increased during the whole breeding period, but cultivars from several years (1958, 1981, 2000, 2010) had lower HI than earlier released cultivars which may suggest that breeding goals pointed towards double purpose wheat. The number of spikes per m2 increased considerably in the last two decades of breeding explaining most of the grain yield increase. Thousand kernel weight (TKW) did not show noticeable changes in the last 100 years. Grain protein decreased from 15.0% in old cultivars to 11.7% in modern cultivars. The breeding success in Uruguay over the last 100 years is comparable to the progress achieved in other Latin-American countries with national breeding programs. Nowadays, breeding efforts are mainly focused on disease resistance and grain quality improvement. However, breeding strategies in future should also focus on nutrient use efficiency by increasing N uptake and N grain accumulation.