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Home > Our Products > Technical & Safety Info > For the Record - Science > Drought Tolerance

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Drought Tolerance

What countries are impacted by drought?

Drought stress affects many farmers globally every year. About half of the world's countries are affected by drought, with developing countries most severely affected. The Dust Bowl days of the 1930s affected 50 million acres of U.S. land, rendering farmers helpless. More recently in the U.S., agriculture losses totaled $44 billion in 1980, and the drought of 1988 affected at least 35 states with losses totaling $56 billion. The Horn of Africa has experienced and continues to experience massive food shortages due to drought. The Darfur conflict in neighboring Sudan, also affecting Chad, was fueled by decades of drought. Drought has impacted more than 13.5 million hectares of farmland in China.

What are the effects of drought on corn?

Corn is adapted to a wide geographic range within the United States, but yield potential is closely related to the amount of available water. Whether it is the higher-producing central Corn Belt or the drier western plains of the United States, the supply of water is a major factor affecting yield and yield consistency. Corn is particularly sensitive to drought stress during flowering, tasseling, silking, and early grain-filling. Eighty-five percent of U.S. corn suffers from varying degrees of drought stress at some time in the growing season. Sporadic drought stress may reduce the profitability of corn farming even in areas that normally receive adequate rainfall. So for many corn farmers, an improvement in the corn plant's ability to withstand drought stress would lead to more consistent and profitable yields. The image below highlights the region in the Western Corn Belt that is particularly sensitive to periods of water stress related yield losses.

How much water does a corn plant require?

The amount of water required by a corn plant depends upon the developmental stage of the plant and the growing temperature. The key developmental phase where the most water is required is during silk development and emergence, pollination and early kernel development. Therefore, it is important to determine if an adequate amount of water is being delivered to the corn plant during each stage as the corn plant grows and matures. It is possible to have average rainfall over the entire growing season but still observe decreased yield. This would occur if too much rain fell at the beginning or end of the growing season and not enough fell during the critical period of yield determination.

The image below shows how water stress affects the corn plant during different key stages of growth. The most sensitive is the Flowering stage which occurs between V10 (10 leaf) and R3 (milk) stages, followed by the Grainfill stage, R1 (silking) through R6 (physiological maturity). Stress during the Flowering stage results in fewer ears and kernels/ear while stress during the Grainfill period causes reduction in kernel size.

Monsanto's Technological Progress on Drought Tolerant Corn

Monsanto's current plant biotechnology portfolio contains a trait that has been shown to provide a yield benefit under certain dry soil conditions. Corn containing the YieldGard^® Corn Rootworm trait lessens the effects of drought stress by protecting the roots of the plants from insect damage, thereby enabling the roots to absorb more water and nutrients than non-protected plants. Corn containing the YieldGard^® Corn Borer trait also contributes to higher yield through its built-in protection from corn borer damage in stalks, which improves flow of available water and nutrients.

Over the last several years, Monsanto scientists have focused biotechnology resources and expertise on the discovery and development of additional drought-tolerance approaches. Monsanto' s genomics discovery program has focused on identifying genes that improve a plant's ability to reduce the effects of drought stress on grain yield, resulting in several candidate genes for introduction and testing in corn. Since 2003, Monsanto has successfully demonstrated that some of these candidate genes enhance the drought tolerance of corn hybrids in the field.

Monsanto is now working to fully evaluate these candidate genes in corn and to produce the commercial events that will provide the performance and consistency that growers demand. Monsanto' s breeding program also is focusing on ensuring the availability of adapted germplasm that performs well under drought stress to maximize the benefits of drought-tolerance traits. Drought-tolerance traits are expected to be provided in combination with the insect-resistance and herbicide-tolerance traits desired by growers, following extensive performance evaluations and quality testing and approval by government regulatory agencies.

Monsanto' s Biotech Pipeline and Drought Tolerant Corn

Monsanto has a robust biotech pipeline investigating genes that impart a variety of traits for increasing yield and reducing the negative impact of biotic and abiotic stresses. One candidate gene produces an RNA chaperone that surprisingly mitigates water stress and stabilizes yield under water limiting conditions. The expression of this gene in corn plants reduces the effects of periodic water stress and has achieved the goal of 8 to 10% average yield advantage under water stress conditions (Castiglioni et al., 2008). A second candidate gene produces an NFB2, a native plant protein that acts as a transcription factor for regulating the expression of other genes in corn plants. Specific expression of NFB2 transcription factor helps the corn plant tolerate drought conditions, leading to improved seed set and yield (Nelson et al., 2007). The genes for producing NFB2 and RNA chaperone are two examples of Monsanto's robust pipeline that continues to focus on bringing the best genetics and traits to the farmer.