Hardpan penetration ability of wheat roots

This project, funded through the new GRDC initiative ‘Root Systems for Australian Soils’, builds on current and past research undertaken in WA that has described the pattern of root growth of annual crops in a range of field soils with chemical and/or physical barriers to growth, including hard soils and drought. It is not known whether genetic diversity exists for root growth in soils containing a hardpan among the currently-available wheat cultivars and breeding lines. Genotypic variation in root penetration ability has been reported in other cereals (Yu et al. 1995; Kubo et al. 2004), and validated in our own research, using a pot technique where a thin disc of wax and petroleum jelly is placed in a soil column to simulate a hardpan (Botwright Acuna and Wade 2005). Partitioning of the soil column by the wax layer makes it possible to examine the interaction between hardpan strength and soil moisture stress. Our pot experiments have revealed differences in root penetration ability under drought among 24 wheat cultivars and breeding lines. These results are compared with observations on their rooting depths in two contrasting soil types in field experiments undertaken in Merredin. This technique will have application in identifying promising lines for wheat breeding programs and in the interpretation of field performance of wheat grown in soils containing a hardpan.