While Jonathan Richards’ team in the LSU AgCenter Department of Plant Pathology and Crop Physiology focus on all kinds of diseases impacting crops in Louisiana, recently there’s been one pathogen that has taken up much of their attention.

“I’d say the biggest focus in our last year’s work is looking at differences in gene expression between different soybean varieties in response to infection by Cercospora sojina, which causes frogeye leaf spot,” Richards said.

Richards, an associate professor, has been working on ways to capitalize on genetic and molecular variation in soybean plants to develop resistance to dangerous pathogens, like Cercospora sojina and Xylaria necrophora, the fungus that causes taproot decline.

Richards has been researching which genes are activated in soybean varieties that are resistant to these fungi and which ones are not in varieties that are highly susceptible. This will shed light on which genes could have a beneficial effect by being deployed in new varieties.

In the past year, Richards has also begun researching how applying flavonoids onto plants may change their ability to resist infection after studies showed that older leaves are less susceptible to infection than younger leaves.

The older leaves showed an increase in gene expression of several molecular pathways, including those that produce different flavonoids, and so Richards began experimenting with the application of flavonoids onto younger leaves with the hopes of inducing resistance. From these experiments there was not a clear indication that the application of flavonoids was helpful, but scientists are still experimenting with different application methods to see if that changes their effectiveness.

They are also going to run more experiments around the differences in gene expression between younger and older leaves to find out what genes may be impacting this change in resistance in the older leaves.

Taproot decline, caused by Xylaria necrophora, is also an emerging threat of soybeans. Richards plans on using similar genetic and molecular methodologies to investigate resistance to this disease, too.

“The Doyle lab has done a lot of work on developing the screening methods that we can use to identify resistant or susceptible soybean varieties to taproot decline,” Richards said, referring to plant pathologist Vinson Doyle. “That project is still ongoing, and we’re hopeful that we’ll be able to apply some of those methods to understand what the differences are in terms of resistance to taproot decline among different soybean varieties and eventually pinpoint specific resistance genes.”

More recently, Richards and his team have begun researching which genes are conserved among soybean fungal pathogens and predicting their virulence functions. Their idea is that if they can find and silence those genes, they may be able to develop a strategy that will reduce infections greatly.

“The idea here is that we might have a very conserved gene that’s present in different species of fungi that all can infect soybean,” Richards said. “So then if we can target the same gene as part of a novel management practice, that might be able to help control several different diseases at once. We have identified several promising candidates and are now close to testing their functions”