Co-PIs: Kathleen Brown (Pennsylvania State University), Shawn Kaeppler (University of Wisconsin-Madison), George Kanyama-Phiri (Bunda College of Agriculture, Malawi)
Senior Personnel: Moses Maliro (Bunda College of Agriculture, Malawi)
Drought is a primary constraint to crop production in developing countries. Development of drought tolerant maize varieties will be an important contribution to food security in these regions. The overall goal of the project is to identify and characterize maize varieties with expanded root cortical aerenchyma (RCA) traits, which has been shown to enhance water and nutrient acquisition from soil. The project will characterize the physiological phenotypes of RCA traits from US and African maize germplasm, genetically map the RCA traits, and evaluate selected maize varieties in southern Africa in field stations and through on-farm trials. Such agroecological study in Africa will assess potential RCA trait interactions with nutrient acquisition, radial nutrient transport, mycorrhizal colonization, and susceptibility to root pathogens. In addition to drought, RCA may also enhance acquisition of limiting soil nutrients such as phosphorus and nitrogen.
Defining and understanding traits enhancing drought tolerance is of great importance to smallholder agriculture in developing countries. This project will provide physiologically validated phenotypic traits, germplasm sources, and molecular markers that can be applied in maize breeding programs towards drought tolerance. The project includes collaboration with plant breeders in Africa and Latin American to ensure connection and transfer of outcomes to smallholder farmers. With respect to training, case studies on African agriculture will be developed for undergraduate courses at the Pennsylvania State University and the University of Wisconsin.
Access to project outcomes Project outcomes will be accessible through the USDA-ARS National Plant Germplasm System (www.ars-grin.gov/npgs), the Maize Genetics and Genomics Database MaizeGDB (www.maizegdb.org), and an outreach web site to breeders which is available in English, French, Portuguese, and Spanish (http://roots.psu.edu/?q=en/methods).
In developing nations, drought and low soil fertility are primary causes of food insecurity and the environmental degradation and social unrest that it causes. In rich nations, intensive fertilization is the greatest environmental and energy cost of crop production. Global climate change and a growing human population are intensifying these problems. The creation of new tools to improve the drought tolerance and nutrient efficiency of staple crops therefore has substantial relevance to the ability of our species to sustain itself despite a growing population and environmental degradation. Our project focused on a root trait, root cortical aerenchyma (RCA), that improves the efficiency of soil exploration by the root system. RCA results in air spaces forming in the root as a result of cell death. Since these cells are lost, there are fewer cells per unit of root length that require resources from the plant, therefore the root is "cheaper". When roots are cheaper, there are more resources available for additional root growth, allowing roots to reach the deeper layers of the soil, where water is often still available even during a drought. We demonstrated that high RCA genotypes of maize performed better under drought in fields in the US and Malawi. During our studies of RCA, we found two new anatomical traits that also contribute to root cost. We developed molecular tools to allow plant breeders to easily select high RCA genotypes in their breeding programs. With knowledge of the benefits of RCA and other anatomical traits, and methods for selecting these traits, plant breeders will now be able to create more drought-tolerant cultivars of maize. We invented a new method, laser ablation tomography, to permit three-dimensional visualization of the cell and tissue structures of roots and other biological samples. This method will be useful for understanding anatomical traits in plants and other multicellular organisms, as well as interactions between and among organisms such as those plants with fungi or insects.
