An international team of scientists funded by USDA’s National Institute of Food and Agriculture (NIFA) has learned remarkable things about how fungi evolve to cause disease on crop plants. This novel information will help develop new ways to protect plants from these pathogens.  The team was led by researchers at USDA’s Agricultural Research Service, the Broad Institute and the University of Amsterdam in the Netherlands.  Their results were reported in the March 18 issue of the journal, Nature.

The researchers unlocked genetic secrets of the plant pathogenic fungi in Fusarium oxysporum, which causes a variety of diseases in economically important crops. Some of the fungi within this species cause disease on bananas, while others infect tomatoes, canola, melons or cotton. Not only do these fungi cause plant diseases that decrease crop productivity, they also produce toxins that threaten the health of animals that eat the infected plants.

Researchers discovered that there are specific chromosomes present in a subset (lineage) of the fungi within F. oxysporum that are not present in all of the fungi within the species.  The fungus needed the presence of a specific set of chromosomes to cause disease on a specific crop plant.

To control plant diseases caused by these fungi, crop plants have traditionally been bred to be disease resistant.  Unfortunately, the fungal pathogens are adept at circumventing the plant host resistance, thus allowing disease to occur again.  The researchers wanted to better understand how these fungi can evolve so rapidly to cause different diseases on different crop plants.

For the first time, these researchers have experimentally demonstrated the transfer of two of the lineage-specific chromosomes between strains of F. oxysporum.  The transfer of the lineage-specific chromosomes converted a non-disease causing strain of the fungus into a strain that does cause disease. This result is remarkable because it has led to a better understanding of how pathogens can evolve.  It also demonstrates that, in nature, large amounts of genetic material (an entire chromosome) can be transferred between two fungi that were not related as parent and offspring.

NIFA funded this project through the National Research Initiative’s Microbial Genomics program. Through federal funding and leadership for research, education and extension programs, NIFA focuses on investing in science and solving critical issues impacting people's daily lives and the nation's future. For more information, visit www.nifa.usda.gov.