Resistance screening for aerial blight is established in a greenhouse at the Plant Material Center in Baton Rouge. Sprinklers mimic the wet conditions that favor the pathogen. Photo provided by Sara Thomas-Sharma.

Efforts to identify soybean varieties resistant to aerial blight are underway at the LSU AgCenter, with plant pathologist Sara Thomas-Sharma leading a greenhouse screening project aimed at improving management of the disease.

Thomas-Sharma screened 24 core block soybean varieties selected from the annual variety trials and germplasm screenings. The varieties were tested under controlled greenhouse conditions to assess their resistance to aerial blight.

“We did the trial twice. Unfortunately, there was a lot of variability between the two trials, and none of the varieties showed up as being consistently resistant,” Thomas-Sharma said.

The trials, conducted in December and January, may have been affected by colder temperatures despite the greenhouse setting.

“The greenhouse is fairly weatherproof, but I think when it’s really cold outside, the temperatures do drop inside,” Thomas-Sharma said.

To address this, the next trials are being conducted during the summer to minimize environmental variability.

Aerial blight, caused by a soilborne pathogen, presents unique challenges for field screening because of its patchy distribution.

“When you do screening in the field, it’s very patchy, so you don’t get uniformity of the inoculum,” Thomas-Sharma said. “The purpose was really to remove that out by having a greenhouse assay where you can control that you’re putting a uniform amount of inoculum on all the plants.”

While no resistant varieties were identified, the research provides valuable insights for growers in high disease pressure areas.

“If you’ve had a history of the disease, it’s most likely going to come back, because it’s in the soil,” she said. “You could use this information to see if maybe between two varieties you could use a different variety.”

Fungicide resistance in the pathogen population further complicates management.

“There is a fungicide resistance problem with this pathogen population,” Thomas-Sharma said. “We have done a much smaller study, and we have picked up resistance to commonly used fungicides, but we’ve not confirmed it across the state.”

Ultimately, the goal is to support integrated disease management.

“In plant pathology, we always talk about integrated management where you’re not relying on just one tool,” Thomas-Sharma emphasized. “Host resistance or growing a variety that’s resistant to a particular disease is a big component of integrated management.”

Resistance screening for aerial blight is established in a greenhouse at the Plant Material Center in Baton Rouge. Sprinklers mimic the wet conditions that favor the pathogen. Photo provided by Sara Thomas-Sharma.

Fungal structures found on an infected soybean plant will fall to the ground to allow the aerial blight pathogen to survive in the soil. Photo provided by Sara Thomas-Sharma