Photos courtesy of AAFC: Soybean responses to Phytophthora sojae. Root rot|
disease can cause major damage to soybean fields
A new and unusual discovery by Agriculture and Agri-Food Canada (AAFC) represents
the first time a pathogen has broken Mendel's Law, a genetic law that states how
characteristics are passed on through inheritance. This discovery could impact the
control and management of soybean root rot disease, a major problem worldwide. A
paper highlighting this discovery recently appeared in the scientific journal
Soybeans are one of the most important crops in the world's food supply, but they
are vulnerable to soybean root rot, a disease caused by Phytophthora sojae. AAFC
research scientist Dr. Mark Gijzen is part of a team that discovered a previously
unknown way in which the soybean root rot pathogen is able to defeat plant resistance
and adapt for survival. With this new information, scientists will alter how they
study the pathogen to create better targeted methods of control and management of
the disease, in turn helping producers and the soybean industry.
Dr. Gijzen discovered that virulence in P. sojae is passed on, but not through the
normal means of inheritance from parent organisms to their offspring described by
Mendel's laws. The pathogen actually breaks Mendel's laws and uses something called
transgenerational gene silencing to pass on traits that enable it to infect and
kill soybean plants.
"This is an extremely unusual phenomenon we've never seen before," says Dr. Gijzen.
Working with a team of experts from Oregon State University and Nanjing Agricultural
University (China), Dr. Gijzen is researching methods for detecting, monitoring
and controlling P. sojae.
"Transgenerational gene silencing is an epigenetic phenomenon, meaning the unit
of inheritance is not the DNA sequence of the gene but rather some other self-propagating
factor; in this case we believe it to be small RNA molecules. This has big implications
that will affect the evolution of this pathogen and how we control it."
In Canada, soybeans are grown on 1.5 million hectares in Ontario, Manitoba, Quebec
and Prince Edward Island. Soybean root rot causes widespread damage amounting to
annual production losses of $40-50 million in Canada and $1-2 billion worldwide.
Agriculture and Agri-Food Canada has made significant contributions to studying
the disease since its first appearance in southern Ontario in the 1950s.