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Improving water acquisition in maize with root traits that reduce the metabolic cost of soil exploration

We propose to employ recent discoveries in root biology to develop maize varieties with enhanced acquisition of soil resources by exploiting genetic variation for root traits that reduce the metabolic cost of soil exploration.

Results of this project are available (Oct 2013).

PI: Dr. Jonathan Lynch (The Pennsylvania State University)

Co-PIs: Dr. Kathleen Brown  (The Pennsylvania State University), Dr. Shawn Kaeppler (University of Wisconsin-Madison), Dr. George Kanyamaphiri (Bunda College of Agriculture, Malawi)

Funding Source: NSF - Basic Research to Enhance Agricultural Development (BREAD)

Research Goals:

Drought is a primary constraint to maize (Zea mays) production in developing countries. Development of maize varieties that are better able to acquire water from drying soil would be an important contribution to food security in these regions. We propose to employ recent discoveries in root biology to develop maize varieties with enhanced acquisition of soil resources by exploiting genetic variation for root traits that reduce the metabolic cost of soil exploration. 

We have recently discovered that maize genotypes with large root cortical aerenchyma (RCA) and small cortical cell area (CCA) have less root respiration, greater root elongation, deeper roots, and greater acquisition of water from drying soil. A field study showed that natural variation for RCA among closely related genotypes resulted in 800% variation in yield under water stress. We have developed a high-throughput method to evaluate these traits in maize germplasm, tools to identify the genetic control these traits, and research sites in the USA and Africa to evaluate their relationship with stress tolerance. The primary goal of this project is to deploy these traits for the development of maize genotypes with greater tolerance to drought. 

High and Low RCA

The root cross section on the left exhibits a large amount of aerenchyma, which is air filled space formed after cortical cells die. The section on the right shows cortical tissue with no aerenchyma.

This work will include: 

1) Confirmation of the physiological utility of RCA and related traits for drought tolerance in controlled settings in the USA. 

2) Analysis of natural genetic variation for RCA and related traits including phenotypic profiling of regional maize lines and diversity panels; development of genetic stocks for high-resolution mapping and detailed phenotypic dissection; and discovery of quantitative trait loci controlling RCA to enhance breeding methods and facilitate gene discovery. 

3) Evaluation of the agroecological utility of RCA and related traits in southern Africa in field stations and on-farm trials, considering other stress factors present in these agroecosystems. 

Broader Impacts

This research will generate fundamental new knowledge of root traits that regulate soil resource acquisition. The utility of these traits for drought tolerance has never been investigated. This project would also identify novel traits, germplasm sources, and genetic markers for crop breeding. In addition to drought, RCA may be useful in the acquisition of limiting soil nutrients such as phosphorus and nitrogen. 

The proposed research will translate fundamental physiological and genetic information into products and approaches that will help to feed hungry people in Africa.  Training activities are focused on the interaction between African and US scientists.  Post-doctoral researchers funded at Penn State will participate in research conducted in Africa thereby gaining an appreciation of the practical challenges of translating basic knowledge into products for this region.  Infrastructure in Africa will be strengthened by training African students at US institutions. This interaction will also be taken back to the classroom.  A case study related to this research will be utilized in Lynch's undergraduate course in Plant Nutrition and in Kaeppler's undergraduate Plant Breeding and Biotechnology course (each has ~30 students per year). 

This project addresses novel scientific issues that are of demonstrable relevance to human welfare.