Maize Seedlings Predict Drought Tolerance

Newswise — Scientists have developed a new method for measuring drought tolerance in maize. By comparing the shoot-to-root ratio in seedlings stressed by low water, scientists can predict whether a plant has the right mix of genes for adapting to drought conditions.

The ideal drought-resistant maize should have a higher ratio of root surface area compared to leaves and stems. Developing enough adult plants to determine this feature is a costly investment. The research, conducted by Nathinee Ruta at the Swiss Federal Institute of Technology, tested whether the root to shoot ratio in seedlings subjected to water stress would provide the basic genetic information about the general pattern of root system architecture leading to drought avoidance. The findings were reported in the July/August 2010 edition of Crop Science, published by the Crop Science Society of America. The study was conducted at Peter Stamp’s laboratory at the Swiss Federal Institute of Technology (ETH) in Zurich, using maize populations developed by the breeding program of the International Maize and Wheat Improvement Center (CIMMYT), headquartered in Mexico. These maize lines were developed to increase yield in drought-prone environments such as Sub-Saharan Africa. Therefore, the data on seedling roots could be compared with yield trials in drought environments that had been generated throughout several years. The roots of these seedlings grew on filter paper in growth pouches and were measured non-destructively using digital image analysis. The system was kept simple to allow for a handling of 200 plants per day. This was a sufficient amount of data to allow researchers to locate the positions of the genes that control root growth, and link them to other genes in the maize genome. Most genetic studies of water stress of maize tend to focus on the above ground portion of the plant, with the roots not easily accessible, particularly under drought conditions. With little known about the correlation between root structure and drought tolerance, this research offers promising prospects for using root traits in predicting maize yield under water stress. “There is probably an optimal maize ideotype for each combination of soil type and climate condition,” stated Andreas Hund, the senior scientist leading the project. “We aim to define these ideotypes for contrasting environments and identify key loci allowing us to select for more efficient root systems.” Research is ongoing at ETH to improve techniques to measure genetic relationships between leaf and root surface area as they respond to environmental conditions. A strong focus will be on how these factors change over time or with respect to environmental stresses, such as extreme temperatures or drought.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at http://crop.scijournals.org/cgi/content/full/50/4/1385.

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