Location: Floral and Nursery Plants ResearchTitle: Evaluation of Hydrangea Cultivars for Tolerance Against Root Rot Caused by Fusarium oxysporum
|NEUPANE , SANDHYA - Tennessee State University
|BAYSAL-GUREL , FULYA - Tennessee State University
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2023
Publication Date: N/A
Interpretive Summary: Root rot caused by Fusarium oxysporum is a newly identified disease in oakleaf hydrangea. In order to evaluate the resistance among hydrangea species and cultivars against root rot, ARS and Tennessee State University scientists in McMinnville, Tennessee evaluated fifteen hydrangea cultivars from four species for root rot resistance. Rooted cuttings of each cultivar were inoculated with either F. oxysporum or water, and root rot severity was assessed after four months. All species and cultivars tested were susceptible to root rot. Oakleaf hydrangea was the most susceptible species while smooth hydrangea (Hydrangea arborescens), bigleaf hydrangea (H. macrophylla), and panicle hydrangea (H. paniculata) showed some tolerance compared to oakleaf hydrangea. Among oakleaf hydrangea cultivars, Snowflake, John Wayne and Alice were the three most tolerant cultivars. These results are being used to determine management options for root rot in container and field grown oakleaf hydrangea production.
Technical Abstract: Root rot caused by Fusarium oxysporum Schltdl. is a newly identified disease in oakleaf hydrangea. Some cultivars such as Pee Wee and Queen of Hearts grown a in pot-in-pot container system in a Tennessee nursery showed symptoms after late spring frost in May 2018 with 40% and 60% incidence respectively in the infected nursery. This experiment was carried out to evaluate the resistance among different hydrangea cultivars against root rot caused by F. oxysporum. Fifteen hydrangea cultivars from four different species were selected and rooted cuttings were prepared from new spring flushes. Twelve plants from each cultivar were transplanted into one gallon pots. Half of transplanted plants (6 single plants) were inoculated by drenching 150 mL conidial suspension of F. oxysporum maintaining the concentration of 1×106 conidia/mL. Half of the plants remained non-inoculated (control) and were drenched with water. After four months, root rot was assessed using a scale of 0-100% and recovery of F. oxysporum was recorded by plating 1 cm of root in Fusarium selective medium. Fusaric acid (FA) and mannitol were extracted from the roots of inoculated and non-inoculated plants to see the effect and role on pathogenesis. Further, mannitol concentration was analyzed using absorption wavelength in spectrophotometer and FA was analyzed using and high-performance liquid chromatography (HPLC). Results indicate no cultivars were resistant to F. oxysporum. Hydrangea arborescens, H. macrophylla and H. paniculata were less susceptible compared to cultivars from H. quercifolia. Among H. quercifolia, cultivars Snowflake, John Wayne and Alice were less susceptible.