Study a step toward disease-resistant crops, sust...(Johal said. We've identified most of th...)

Any genes discovered also could benefit other plants; all use the same pathway to fight infection, Johal said.

"The same approach could be used in other organisms, such as in animals," he said. "And insights could also apply to human disease."

To map genes, scientists often cross mutant plants with crop lines that have well-described genetics. In doing so, they usually try to reduce or eliminate the impact of unknown natural variants so the information they're looking for - typically regarding the mutant gene - is not altered.

"To date most of us were taught in genetics class that when you find a mutation, for example in corn, you cross it with corn from different backgrounds, pick the background where the mutant's appearance, or its phenotype, is the most dramatically altered, and then find the genetic changes that cause the phenotype," Weil said.

But Weil and Johal are instead looking for natural genes that either enhance or diminish certain traits.

"We are basically 'mining' natural variation for genes of interest," Weil said.

The research started when Johal crossed a mutant gene that affects lesions to a couple of different inbred lines of corn. In one cross it disappeared; in another it became toxic.

"We figured the natural variations in these two inbreds were having a huge effect and decided to take advantage of a large, existing set of mapping data for the two inbreds to find out why," Weil said.

Another example is sweet corn, Johal said. The varieties most people are familiar with derive from a specific mutation that originally rendered sweet-tasting kernels small and shrunken. But researchers bred it with various lines - effectiv
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