Genes Discovered Enabling Tomatoes To Resist Wilt Disease

April 23, 1997

Rehovot, Israel -- April 23, 1997 --A group of genes that makes tomatoes resistant to wilt disease has been discovered in an Israeli-American study headed by Prof. Robert Fluhr of the Weizmann Institute of Science. The finding, reported in the current issue of The Plant Cell (Volume 9, No. 4, pp. 521C532), is expected to speed up the breeding of new disease-resistant varieties and reduce the need for chemical spraying.

Wild tomatoes -- but not cultivated varieties -- are naturally resistant to wilt disease spread by the soil-borne Fusarium oxysporum fungus (lycopersici strain). Once a widespread blight plaguing tomato crops, Fusarium wilt disease was largely brought under control through classical breeding techniques. However, breeding new varieties through this method is a laborious process that can take years because it entails producing many successive generations of hybrid plants in which the undesirable traits have been eliminated but the beneficial ones retained.

The new study facilitates this process by providing molecular markers allowing breeders to simply trace the genetic makeup of new hybrids rather than test for it at each stage. The findings also pave the way for genetically engineered new varieties with an optimal mixture of desired properties.

"In the absence of genes that endow plants with natural resistance to disorders such as wilt disease, farmers must rely on extensive chemical spraying and soil treatment," says Prof. Fluhr, a member of the Weizmann Institute's Plant Genetics Department.

"By imparting natural self-defense capabilities to plants," Fluhr says, "we reduce the amount of dangerous chemicals entering the environment."

Collaborating with Prof. Fluhr were departmental colleague Dr. Dvora Aviv and doctoral student Naomi Ori, along with Prof. Dani Zamir and doctoral student Yuval Eshed of the Hebrew University of Jerusalem's Faculty of Agriculture and Prof. Steve Tanksley of Cornell University.

The newly identified genes are also of primary importance because they form the plant's first line of defense against Fusarium attack. Acting as regulatory switches, they induce the release of various defensive agents such as destructive oxygen molecules that bombard the disease-causing organism, or enzymes that chew away at it.

"A better understanding of how the resistance genes work should allow us to turn on these defense components at will," Fluhr says.

"Moreover," he adds, "the methodology we have helped develop for isolating resistance genes should make it possible to design new resistance genes and transfer them to various crops where they are lacking."

Plant versus Fungus Fusarium wilt disease is caused by a fungus that penetrates the plant roots, primarily through wounded tissue. The fungus works its way into the plant's vascular system -- the vital passageway for water and nutrients -- where it thrives. Not only does the Fusarium fungus have a hearty appetite and consume the plant's nourishment, but it also produces toxins. The presence of abundant fungus, therefore, leads to the functional collapse of the vascular system, systemic wilting and often death of the plant.

In the study, the scientists first determined the chromosomal location of the wilt resistance such as one endowing tobacco leaves with resistance to viruses and another that makes the leaves of a weed resistant to bacteria. This resemblance is intriguing since the plant's mechanism for defending the vascular system is very different from the one used for defending leaves.

When a leaf is invaded, the plant can choke off the precise area under siege, killing infected tissue along with the infiltrator but leaving the rest of the plant intact. But when countering an attack on the vascular system -- its essential lifeline -- the plant must employ more precise strategies, such as producing special cellular structures that confine the fungus to the lower part of the root and thus localize the disease.

"Not only do the products of diverse plant resistance genes share structural features," says Fluhr, "but one such feature, resembling a component of biological receptors, can be found in animals as well. This underscores the unity of the plant and animal kingdoms."

The study was supported by the United States-Israel Binational Agricultural Research and Development Fund, the Israel Ministry of Science, the Commission of the European Communities and the Leo and Julia Forchheimer Center for Molecular Genetics at the Weizmann Institute.

Prof. Fluhr is the coordinator of the Israel Ministry of Science's Plant Genome Center at the Weizmann Institute, which involves scientists from several major research institutions in Israel. The Center is aimed at putting Israel on the map of plant genome efforts worldwide, primarily by providing technology for map-based cloning and isolation of genes.

American Committee for the Weizmann Institute of Science

Related Fungus Articles from Brightsurf:

International screening of the effects of a pathogenic fungus
The pathogenic fungus Candida auris, which first surfaced in 2009, is proving challenging to control.

Research breakthrough in fight against chytrid fungus
For frogs dying of the invasive chytridiomycosis disease, the leading cause of amphibian deaths worldwide, the genes responsible for protecting them may actually be leading to their demise, according to a new study published today in the journal Molecular Ecology by University of Central Florida and the Smithsonian Conservation Biology Institute (SCBI) researchers.

Researchers look to fungus to shed light on cancer
A team of Florida State University researchers from the Department of Chemistry and Biochemistry found that a natural product from the fungus Fusicoccum amygdali stabilizes a family of proteins in the cell that mediate important signaling pathways involved in the pathology of cancer and neurological diseases.

The invisibility cloak of a fungus
The human immune system can easily recognize fungi because their cells are surrounded by a solid cell wall of chitin and other complex sugars.

Taming the wild cheese fungus
The flavors of fermented foods are heavily shaped by the fungi that grow on them, but the evolutionary origins of those fungi aren't well understood.

Candida auris is a new drug-resistant fungus emerging globally and in the US early detection is key to controlling spread of deadly drug-resistant fungus
Early identification of Candida auris, a potentially deadly fungus that causes bloodstream and intra-abdominal infections, is the key to controlling its spread.

Genetic blueprint for extraordinary wood-munching fungus
The first time someone took note of Coniochaeta pulveracea was more than two hundred years ago, when the South African-born mycologist Dr Christiaan Hendrik Persoon mentioned it in his 1797 book on the classification of fungi.

How a fungus can cripple the immune system
An international research team led by Professor Oliver Werz of Friedrich Schiller University, Jena, has now discovered how the fungus knocks out the immune defenses, enabling a potentially fatal fungal infection to develop.

North American checklist identifies the fungus among us
Some fungi are smelly and coated in mucus. Others have gills that glow in the dark.

Tropical frogs found to coexist with deadly fungus
In 2004, the frogs of El Copé, Panama, began dying by the thousands.

Read More: Fungus News and Fungus Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to