In the past, Pantoea bacteria were known to cause two corn diseases: Stewart’s wilt and issues with white spots on leaves and stalk rot. But in 2020 and 2021, something unusual happened in corn fields in Texas’ High Plains region.
In Texas, fungi are the most common cause of corn diseases. However, during the 2021 crop season, sudden, drought stress-like symptoms developed on previously green and healthy corn stands in a fungicidal trial at the Texas A&M AgriLife Experiment Station in Bushland.
The overall yield loss from the affected field averaged about 93 percent. Disease development also spanned across all of the study plots, affecting both treated and nontreated plots alike.
Affected corn plants started to look sick in a weird way. Their leaves had strange, light green, long spots that were a bit see-through with straight edges when the corn grew. As the corn plants grew and made corn, these spots turned brown and dead. The sick corn also didn’t grow well, had unhealthy ears, and often developed stalk rot
In 2021, widespread lodging attributed to stalk rot was observed in a grower’s irrigated corn field, causing widespread loss. Pantoea sp. was recovered from the affected stands. fu
Then in 2022, identical symptoms occurred in a growers’ corn field in seven more counties in the panhandle.
“When scientists tested these sick corn plants, they found a type of bacteria called Pantoea. Diagnosis of symptomatic tissues consistently recovered bacteria. BLAST searches of the partial 16S rRNA sequences of the bacterial isolates identified them as belonging to the genus Pantoea,” researchers noted in the Plant Health Progress journal. “Investigations of the pathogenicity of two bacterial isolates, B566 and B623, under greenhouse conditions relying on Koch’s postulates resulted in the development of symptoms identical to those observed on symptomatic field corn plants.”
When tested on healthy plants, the bacteria responded like the diseased corn stalks. The two bacteria, although closely related to P. ananatis, are distinctly different species
Researchers concluded that the new disease of corn is caused by two Pantoea species that can result in stand decline of infected corn plants.