Webb researches sugarbeet diseases in search of producer applications
Worland – With sugarbeet producers becoming responsible for producing larger amounts of sugar to compensate for decreasing sugar cane acreage, USDA Agriculture Research Service (ARS) Plant Pathologist Kimberly Webb strives to understand sugarbeet diseases.
“As a researcher, we have to evaluate and characterize the diversity of the pathogen population and understand how it interacts with the sugarbeets,” explains Webb. “We have to characterize the interactions. Our main output with USDA is to give growers something they can actually utilize in the field.”
In order for disease to occur, Webb notes that a susceptible host, virulent pathogen and permissive environment must all be present. Without one of the three, symptoms won’t develop.
Research concerning permissive environments looks at the effect of moisture levels, air temperatures and soil temperatures on pathogen growth.
“We have to understand our production regions and how the environments are different,” says Webb. “The same recommendations won’t work in two different regions.”
She also notes that they look at increases of disease over time and overlay the data with environmental parameters.
For Fusarium yellows, for example, Webb says they found there is very little disease at temperatures below 65 degrees Fahrenheit and most occurs above 75 degrees.
“After that, it can get as hot as it wants and there isn’t increasing severity in the disease,” Webb explains. “The other key, especially with resistances, is that as it gets warmer, most plant resistances aren’t as effective because the plant isn’t able to fight off the pathogens.”
As plants are increasingly stressed, whether by heat, moisture or other environmental factors, Webb notes that they are less resistant.
Webb also looks at the host environment and the susceptibility of the sugarbeet to resist pathogens.
“We talk about the genes in the plant that make it able to defend itself and what the plant immune system is,” she explains. “We ask, is that defense similar for all sugarbeet diseases?”
The researchers work with proteomics and genomics to answer those questions.
“In proteomics, we look at the proteins extracted from susceptible and resistant varieties of the plants,” she explains. “The proteins are based on genes that are being expressed during stress.”
Researchers utilize a machine to separate the complex protein sample into smaller-sized fractions to enable them to look at individual proteins.
“We are looking for proteins that are turned on in one sample, but not in another, or for proteins that are more highly expressed,” she explains. “Right now, we are looking at how common these proteins are in all resistant varieties.”
By identifying common proteins, Webb notes that they hope to develop molecular markers that breeders can utilize to identify populations that are more resistant to different diseases.
At the same time that researchers are looking to develop sugarbeet plants to be more effective in fending off pathogens, they are also looking at pathogens to see how they cause diseases.
“We want to understand what genes the fungus has to come up with potential targets for fungicides or to see if we can develop a mechanism that to allow us to turn those genes off in the field,” she explains.
Phylogenetics, or the study of the evolutionary relatedness of organisms, is another tool Webb utilizes in her research.
“It is a population of pathogens that we are trying to protect against, rather than a specific organism,” she explained. “We have to understand how a gene is transferred through a population and how common it is.”
By characterizing populations of pathogens, Webb notes that they hope to identify those genes that are crucial in causing disease.
Webb adds that they have also worked on analyzing how pathogens infect sugarbeets. For example, using genetically modified versions of pathogens, they can observe growth of fungus to understand how it spreads and infects the plant.
Webb is also working to develop and distribute germplasm to seed companies to use in their breeding programs. The germplasm includes novel stress resistance genes.
“In my research, I work with plant breeder Dr. Lee Panella, who is focusing on the breeding and improvement of the germplasm,” says Webb. “He is looking at wild relatives of sugarbeet for sources of resistance, improved drought tolerance and some other agronomic characteristics.”
She continued that while Panella develops the background material necessary, seed companies develop his materials in developing commercial varieties