Diversity on Your Table Case Study – The Corn Crisis of

What led to the problem? In 1970, most corn crops were genetically uniform (identical). In 1970, the Southern Corn Leaf Blight (caused by a fungus) hit U.S. corn crops.

Effects? A trait bred into the corn to increase seed production actually increased the corn’s susceptibility to the fungus. 15% of U.S. corn crops were destroyed the first year – costing about $1 billion. biology.uwsp.edu biology200.gsu.edu

Trying to solve the problem … The process took many years and lots of corn (and money) was lost during that time. Breeders used seeds from older corn varieties (saved in gene banks) to produce new disease-resistant variety of corn.

What we should have learned from this … Low crop diversity increases the chance of devastating diseases. To deal with diseases, we often look for a different genetic variety resistant to that disease that could help current crops adapt to changing conditions.

Have we actually learned this lesson? There are some limited systems in place to increase crop diversity. However, crops in the U.S. have actually become more uniform over the past 40 years rather than more diverse.

1. Gene Banks Place where seeds are saved in cold storage. –A small amount of as many varieties as possible are saved. –Not all seeds “survive” in gene banks – some will not germinate (grow) later. –Not all seeds can even be saved in this manner

2. Cultivation of Rare Plant Varieties There are groups, such as Seed Savers, that share seeds and plants (and even animals) among individuals and organizations. Buying heirloom varieties of seeds/plants (usually through groups or catalogues because not often in stores). Encourages widespread dispersal of these rarer plants – hopefully having them available in the future.

3.Discoveries from Nature (Habitat Preservation) Oftentimes we return to areas where a plant originally evolved and look for varieties not currently being cultivated, but containing beneficial characteristics. Sometimes useful plants exist where we never looked before. Maintaining wild habitats and the original sustainable agriculture is vital.

Discoveries from Nature – For Example: In 1977, a new variety of wild corn was discovered by Rafael Guzman in a remote mountain area of Mexico. Called teosinte: –Can withstand hot, dry weather –Reproduces easily –Resistant to the Southern Corn Leaf Blight

4. Sustainable Agriculture Farming that requires few to no chemical pesticides & fertilizers. Growing crops appropriate to the climate found in that region. –Reduces the need for irrigation and other resource- heavy practices. Growing crops originally found in that region. –Encourages diversity of genetic types worldwide. Planting a variety of crops and maintaining reasonable number of animals. –Animal waste can be dealt with on the farm rather than polluting larger environment. –Farmers investment is protected by diversity of plants if weather conditions or disease affect one type of plant.

Why should we care about crop biodiversity worldwide? Most of the major food crops in the U.S. come from other parts of the world. Many of these are rare or endangered. Habitat destruction prevents the chance of future discoveries of genetic varieties.

Importance of Crop Biodiversity in the U.S. 20% of the 20,000 plants native to the U.S. are in need of conservation. 80% of endangered plants in the U.S. have close relatives that are economically and/or agriculturally important. Approximately 750 threatened and endangered plants in the U.S.

14 ENDANGERED PLANTS OF THE US

15 ENDANGERED PLANTS OF THE US

16 ENDANGERED PLANTS OF THE US

17 ENDANGERED PLANTS OF THE US

Questions to Consider: 1.Why is it so common for farmers to plant monocultures of genetically uniform crops? 2.Why should we care if all our crops are the same as long as we grow enough to feed everyone? (What is the problem with monoculture?) 3.How can we preserve strong genetic and species diversity?