Full text
Abstract
In developing nations, low soil nitrogen (N) availability is a primary limitation to crop production and food security, while in rich nations, intensive N fertilization is a primary economic, energy, and environmental cost to crop production. It has been proposed that genetic variation for root architectural and anatomical traits enhancing exploitation of deep soil strata could be deployed to develop crops with greater N acquisition. Here we provide evidence that maize (Zea mays L.) genotypes with few crown roots (crown root number: CN) have greater N acquisition from low N soils. Maize genotypes differed in their CN response to N limitation in greenhouse mesocosms and in the field. Low CN genotypes had 45% greater rooting depth in low N soils than high CN genotypes. Deep injection of 15N-labeled nitrate showed that low CN genotypes acquired more N from deep soil strata than high CN genotypes, resulting in greater photosynthesis and total nitrogen content. Under low N, low CN genotypes had greater biomass than high CN genotypes at flowering (85% in the field study in the US and 25% in South Africa). In the field in the US, 1.8x variation in CN was associated with 1.8x variation in yield reduction by N limitation. To our knowledge, this is the first report of the utility of CN for nutrient acquisition. Our results indicate that CN deserves consideration as a potential trait for genetic improvement of nitrogen acquisition from low N soils.
