Abstract:

Double-cropping using the wheat?soybean sequence is a common practice in Argentina to promote the intensification of crops within rotations. However, the late release of the fields by a delayed harvest time in wheat determines soybean yield penalizations. In this context, barley could represent a better option than wheat preceding soybean in the crop rotation since there is some evidence that finishes its cycle earlier than wheat. However, it is not clear which period of barley shortens crop cycle allowing an earlier field release than wheat. The objectives of this study were to compare wheat and barley in terms of (i) field release and (ii) grain weight determination through the analysis of their physiological mechanisms. Field experiments during two consecutive growing seasons testing five different environments (three sowing dates in 2007 and two in 2008) were carried out to analyze the duration of different ontogenic periods and the attributes (dry matter and water dynamics) determining grain weight during the grainfilling period in wheat and barley. Early flowering time was the main cause of the early field release by barley as the grain filling and drying period were similar in both species. A strong relationship was found between dry matter and water dynamics in both species. Barley reached a higher maximum water content than wheat and also achieved physiological maturity with higher moisture concentration than wheat (48% and 39%, respectively). Barley showed a slight increase in grain weight, respect to wheat, due to a source:sink ratio enhancement (4% and 9% for wheat and barley, respectively). These data show an opposite response to that of Mediterranean, Australian and UK environments, where barley was under stronger sink limitation than wheat during the grain-filling period.

Author affiliation: Alvarez Prado, Santiago. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Author affiliation: Gallardo, Jose Manuel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Author affiliation: Serrago, Roman Augusto. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Author affiliation: Kruk, Betina Claudia. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Author affiliation: Miralles, Daniel Julio. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Abstract:

The objective of this study is to update the data of genetic progress in bread wheat cultivars released in Argentina from 1918 to 2011 (emphasizing the last 20 years) characterizing different agronomic traits of interest for breeders. Experiments were carried out with a wide range of bread wheat cultivars and conducted under field conditions without nutritional and water restrictions. Yields showed a significant (R2 = 0.68) tri-linear trend when associated with the cultivar's year of release. Until the 40s, when the first inflection point occurred, the genetic progress in terms of yield was 0.8 kg ha−1 yr−1 (0.02% yr−1). Between 1940 and 1999, yield genetic progress reached its highest value (51 kg ha−1 yr−1; 1.17% yr−1) but changed after 1999 when values became lower compared to the previous period, showing a value of 14 kg ha−1 yr−1 (0.18% yr−1). Changes in grain yield were mostly explained by increases in harvest index and not by those in above-ground biomass. Plant height showed a negative bi-linear trend with the year of release, reaching an inflexion point well before the introgression of semi-dwarfing genes in commercial cultivars. Grain number increased ca. 63% when modern cultivars were compared to older ones, which explains most of the grain yield changes. In contrast to grain number, no significant differences between old and modern cultivars were found for grain weight, with average values of ca. 30 mg grain−1 for all environments explored.

Author affiliation: Lo Valvo, Patricio Javier. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Miralles, Daniel Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Author affiliation: Serrago, Roman Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina