Summer 2008

Field Notes

In Guatemala, CALS research is helping grow disease-resistant tomato hybrids - and international partnerships. Douglas Maxwell

Barely six months into his graduate studies, Jonathan Jacobs BS’07 has already realized something critical about becoming a plant pathologist. And his epiphany had little to do with science.

Instead, it came as Jacobs stood in a dying tomato field in the central highlands of Guatemala, where he was completing a month-long research trip to gather information on a bacterium known as Ralstonia solanacearum. In plants such as potatoes, tobacco, bananas and tomatoes, Ralstonia can produce a devastating wilting disease that can leave plants—and farmers—ruined. And that’s exactly what Jacobs saw surrounding him—acres of limp, wilted tomato plants and a farmer desperate for answers.

“It changed my whole perspective on plant pathology,” says Jacobs, whose trip was funded with a grant from UW-Madison’s Latin American and Caribbean studies program. “To see it right in front of me, it made me want to understand this plant-microbe interaction even more, so that hopefully my research can help to reduce this disease in the future.”

Jacobs is not the first CALS student to have an eye-opening experience in Guatemala, where plant pathology professors Caitilyn Allen and Douglas Maxwell have maintained an active partnership with scientists studying bacterial wilt and other tropical plant diseases. Allen and Maxwell have sent a half dozen students to the Central American country to participate in research collaborations and see firsthand the effects of the tropical diseases they study.

“Few of our students have experience with the kind of devastating crop loss you see in developing countries,” says Maxwell. He notes that geminiviruses—a group of tropical plant viruses that are the focus of his research—have been blamed for destroying up to 20 percent of Guatemala’s tomato crop. “I’ve seen entire fields just abandoned. It’s heartbreaking.”

Yet also motivating. Since turning his attention to geminiviruses in 1998, Maxwell has led a multinational effort to develop hybrid tomatoes resistant to the viruses, which are spread by whiteflies. A seed company in Guatemala now markets four varieties that stand up to the disease.

Four years ago, the breeding project expanded to take on another scourge for farmers in the subtropics: the bacterial wilt caused by Ralstonia. The Guatemala-based team’s efforts are aided by the expertise of Allen’s lab, which has identified the bacterial genes that are active when Ralstonia infects a plant. Trials are still in their early stages, but Maxwell is optimistic.

“We’re growing these tomatoes on two sites, and they look very promising,” says Maxwell. “One of the farmers we work with told us he had never seen tomatoes grow in his field before. He wants seeds right now.”

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