Traits of importance for aerobic rice

Irrigation water is limited and costly and for the Australian Rice Industry based in the Riverina, this has become a major limitation to production. Aerobic production (well-watered, non-flooded) has been proposed to improve water productivity. However, historically in Australia, varieties have been developed for continuously flooded growing conditions and as such the appropriateness of the germplasm to aerobic adaptation needs to be explored. Deeper rooting is one trait that is believed to be associated with improved aerobic performance by ensuring plants are less susceptible to fluctuations in water availability in the top 20 cm of the soil profile. Two field experiments evaluating 20 genotypes were conducted to examine genetic variation and relationships between root traits and grain yield. Two methods for root trait observations were conducted. A basket method was utilised for 15 genotypes in one experiment, while soil cores at maturity were collected from all plots in both experiments. Highly significant (p 0.90). Grain yield had a highly significant genetic correlation (rg= 0.56**) with the percentage of roots below 20 cm at maturity which demonstrated the advantage of a deeper root system in aerobic conditions. Several lines, most notably Australian variety Sherpa, demonstrated high yields in aerobic conditions but only moderate expression of deep roots. These results suggest the incorporation of deep rooting characteristics into high yield potential backgrounds (e.g. Sherpa) has the potential to close the yield gap between aerobic and traditional flooded production.