Genetically vigorous wheat genotypes maintain superior early growth in no-till soils

Abstract

Reduced tillage is widely used in maintaining sustainable agricultural systems. Early growth of wheat (Triticum aestivum L.) is often impaired in the high strength soils typical of no-till. This may reflect the intrinsically reduced vigour of commercial wheat varieties. We investigated how genotypes selected for greater early vigour performed relative to a broader range of wheat genotypes for shoot and root growth in cultivated and no-till conditions. We assessed a range of cereal germplasm varying for early growth (establishment and leaf area development) under contrasting tillage conditions in a very favourable season, and then the performance of a selected subset validated in repacked soil cores in controlled environments. We measured above- and belowground growth, and parameters associated with adaptation to increasing soil strength. High strength soil reduced early shoot and root growth. There were no effects on plant number at emergence and coleoptile length was unimportant. Increased soil strength reduced early growth of all genotypes including genetically vigourous wheats. However, the ranking for vigour was maintained with high strength soil suggesting breeding lines and populations containing genes for greater early growth may still be beneficial in selection for improved performance in no-till. Genotypic increases in specific leaf area and leaf breadth were both associated with genetically greater seedling leaf area and biomass, and potential for greater root growth in no-till. Early growth of all wheats was reduced with no till and the harder, high strength soil associated with this tillage system. Genetic variation was large in no-till and cultivated soils alike. In high strength and no-till soils, the relationship with shoot and root vigour was positive indicating selection for greater early growth in breeding programs may increase leaf area and improve root growth.