Researcher(s)
- Phoebe Baker, Plant Science, University of Delaware
Faculty Mentor(s)
- Alyssa Betts, Department of Plant and Soil Sciences Associate Professor and Extension Specialist Plant Pathology, University of Delaware
Abstract
Pythium root rot (PRR), caused by multiple species of Pythium, is an important disease of corn in Delaware. Infection can result in dead or stunted plants that significantly reduce yield potential of impacted fields. Pythium is an oomycete, or water mold, favored by wet field conditions. Motile zoospores released from structures known as sporangia are important for infection. From previous surveys, P. graminicola is the most abundant species associated with corn infection in Delaware, but few studies have focused on the variation of zoospore production across isolates of P. graminicola. Previously, greenhouse aggressiveness trials were conducted to compare symptom development of ten P. graminicola isolates. At the conclusion of these trials, isolates from infected root tissue were collected and placed into long term storage. Nine of these isolates were selected for the current study to examine sporangia development and zoospore release within each isolate. Three media types, lima bean agar (LBA), potato dextrose agar (PDA), and a V8 based media (V8) were selected to compare sporangial development after 8 days of growth at 21° C under constant light. The trial was repeated three times. Isolates grown on LBA produced significantly more sporangia (p < 0.05). Following sporangia assessment, three 3mm plugs were taken from the nine LBA plates used for sporangia comparison to make 24 hour suspensions for zoospore release. All isolates produced zoospores on LBA, but there was variation across isolates. Two isolates produced significantly more zoospores (avg. 4.6 x 10^4) in all three replications, while three isolates grouped producing fewer zoospores (avg. 1.1 x 10^4). The results of this trial provide insight on the potential for variation in isolate aggressiveness due to zoospore production. This data can inform future selection of isolates to support greenhouse evaluation of breeding germplasm for the development of corn hybrids with resistance to PRR.