[Genetic and agronomic changes that increased wheat yields in Chile] | Los cambios geneticos y agronomicos que incrementaron el rendimiento de trigo en Chile

The continuous rise in the world population combined with virtually stable area figure and lower rate of increase in the wheat yields globally is making it necessary to find alternatives to break the barriers to yield. The area seeded to wheat in Chile decreased by 318 000 ha between 1966 and 1995. However, the increase in yield 1.4t/ha to 3.5 t/ha, during the same period helped to maintain a constant level of production. Political and economic changes were primarily responsible for the above changes. A national campaign to increase yields focused at favorable prices that promoted the use of more technology and inputs, thereby, increasing the use of fertilizers, herbicides and fungicides. Even now other factors such as diseases and insect pests, soil acidity, crop management and subsistence crops effect the yield in several areas. Wheat breeding has played a critical role in increasing the production potential by recommending new varieties resistant to diseases and lodging, representing diverse types and maturity groups and with improved yield potential and industrial quality. The yield of the new varieties developed by INIA frequently surpasses 10 tons per ha in the yield trials and approaches this potential commercially. The yield gap primarily depends on the level of technology used. Wide set of progenitors is utilized in the hybridization program and selections are made under optimum growing conditions. The high yields obtained require a very heavy use of nutrients by the crop, due to high levels of extraction during some critical growth periods, when they need to be made available. The excess or shortage of soil humidity also effects the plant nutrition and the yield components. It has been possible to select for a large spike with high number of grains per spike, but any limitations effecting its development can result in strong differences in the expected potential yields. The number of spikes per unit area, in general, approaches only 50% of the maximum number of tillers and seems to be limited by the number of spikes in a row which manifests independently to the seed rate and the distance between the rows. The grain weight also shows variations at different locations and those caused by the limitations of the available humidity.