Genotypic variation for lodging tolerance in spring wheat: wider and deeper root plates, a feature of low lodging, high yielding germplasm

Abstract Plant lodging reduces yield and quality of irrigated and rainfed spring wheats alike. Local and imported germplasm was screened to identify consistently higher-yielding genotypes with low plant lodging for the north-eastern Australian wheat belt. Using field level treatments, such as fertilisation and tactical overhead irrigation to consistently simulate scenarios leading to lodging in the target region, high reproducibility of lodging rankings was achieved in multi-environment experiments. In separate experiments in two years, detailed phenotyping of selected genotypes in field plots was implemented for traits underpinning stem and root type lodging. Multi-environment and phenotyping experiments ranked genotypes similarly in terms of lodging score. In the phenotyping experiments, root plate spread from field grown plants consistently emerged as a trait able to discriminate low lodging, high yielding germplasm from a multi-trait analysis quantifying genotypic correlations. If the root plate spread was greater than or equal to 5.5 cm, the lodging scores were small, and yield was high. Importantly, root plate spread phenotyped on plants growing at uniform planting density was found to be highly heritable (above 0.80), with a high genotypic correlation (0.80) across environments and strong association with structural rooting depth. A simplified phenotyping approach is discussed based on the main traits driving lodging tolerance and others routinely measured in breeding programs.