Plant pathology graduate student Geona Miles, left, waters soybean seedlings in a growth chamber while talking with research intern Catherine Wilson. Photo by Olivia McClureLSU AgCenter scientists are continuing to unravel what was once termed a “mystery disease.” Now known as taproot decline, the disease hinders root development of crops. In Louisiana, infestations are most often seen in soybeans, killing some plants and robbing others of yield.

AgCenter plant pathologist Vinson Doyle has spent the past few years learning about taproot decline and the pathogen that causes it, Xylaria necrophora. Recently, he and master’s student Geona Miles have been refining inoculation procedures and setting up trials in controlled environment chambers. These advancements are allowing them to search for germplasm that may be resistant to X. necrophora and to document the susceptibility of different soybean cultivars.

It is believed that plant debris in fields helps spread taproot decline. Doyle, Miles and research intern Catherine Wilson began trials this summer investigating how quickly soybean and corn debris colonized by X. necrophora decomposes and how long it is capable of infecting crops. They’re burying both colonized and uncolonized debris in 3D-printed cages and plan on examining it every three months.

“By establishing baseline decomposition rates, we can ultimately look at practices that might speed up decomposition or otherwise modify debris so that it no longer serves as a source of inoculum,” Doyle said.

Another important development has come about through a partnership with Michigan State University. The collaborators have developed a molecular assay to detect X. necrophora in soils and debris — potentially making it easier to gauge the degree of infestation in grower’s fields.

Doyle is encouraged by the progress he and his team have made in the past year.

“If we are able to identify less-susceptible cultivars, we will have tools to predict disease pressure and mitigate its impact,” he said. “We have looked at host responses to increasing inoculum pressure in lab trials and see that as the amount of inoculum in the soil increases, the energy that plants are devoting to defense — rather than growth — increases. This suggests that even moderate reductions in infested debris can lead to a reduction in disease severity.”

Photos below: 1. Plant debris and the 3D-printed cages it will be buried in as part of a study related to taproot decline disease. 2. Plant debris inoculated with Xylaria necrophora, the pathogen that causes taproot decline disease. 3. Several varieties of soybean seedlings sit in a growth chamber. They are being studied for their resistance to taproot decline disease. 4. A soybean seedling inoculated with Xylaria necrophora, the pathogen that causes taproot decline disease, displays lesions and discoloration on its foliage. Photos by Olivia McClure