January 9, 2008

Illinois develops simple lab test to detect soy fungal disease

Southern Illinois University Carbondale developed a simple and cheap laboratory test which detects a costly fungal disease in soy, the Sudden Death Syndrome (SDS).

Scientists said that once the test is commercialized, it will help breeders to produce SDS-resistant soy varieties faster.

David Lightfoot, a biotechnologist in SIUC's College of Agricultural Sciences, said one can do a reliable assay in a greenhouse in a plastic cup and four weeks later, results will be seen. He said that the seedlings develop the leaf symptoms and the root rot or they do not. Labor cost is very low at about US$1 per assay.

Breeding SDS-resistant soy varieties was pretty much tough before. Breeders would plant a beans and hope the disease would show up somewhere by the end of the growing season. If it did, they could make breeding crosses with the survivors and repeat the process during the next season.

Sometimes the disease did not appear, and sometimes when it did, it did not behave normally, disappearing mid-season. Aside from this, breeders also have to look into other traits, such as yield and adaptability, when developing new lines.

Since 1994, Lighfoot and colleagues worked on an assay that could quickly pinpoint seedlings that could withstand SDS.

Lightfoot grew his fungus on a mix of cornmeal, sand, mineral salts and agar, a jelly-like substance made from algae which was enough to keep it alive but not "fat, lazy or happy," He then digs the mix into piles of soil, turning it until the fungus-laden growing medium is distributed evenly throughout. Vulnerable seedlings planted in that infected soil will contract the disease; seedlings with resistance potential would not.