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Sanjel S, Guerra V, Seepaul R, Mackowiak C, Punja ZK, Dufault N, Tillman B, Bradford KJ, Small IM. Application of Hydrothermal Time Models to Predict Sclerotial Germination of Athelia rolfsii. PHYTOPATHOLOGY 2024; 114:126-136. [PMID: 37531626 DOI: 10.1094/phyto-04-23-0132-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
Athelia rolfsii, causal agent of "southern blight" disease, is a soilborne fungal pathogen with a wide host range of more than 500 species. This study's objectives were to (i) quantify the effects of two environmental factors, temperature and soil moisture, on germination of A. rolfsii inoculum (sclerotia), which is a critical event for the onset of disease epidemics and (ii) predict the timing of sclerotial germination by applying population-based threshold-type hydrothermal time (HTT) models. We conducted in vitro germination experiments with three isolates of A. rolfsii isolated from peanuts, which were tested at five temperatures (T), ranging from 17 to 40°C, four matric potentials (Ψm) between -0.12 and -1.57 MPa, and two soil types (fine sand and loamy fine sand), using a factorial design. When Ψm was maintained between -0.12 and -0.53 MPa, T from 22 to 34°C was found to be conducive to sclerotial germination (>50%). The HTT models were fitted for a range of T (22 to 34°C) and Ψm (-0.12 to -1.57 MPa) that accounted for 84% or more of variation in the timing of sclerotial germination. The estimated base T ranged between 0 and 4.5°C and the estimated base Ψm between -2.96 and -1.52 MPa. The results suggest that the HTT modeling approach is a suitable means of predicting the timing of A. rolfsii sclerotial germination. This HTT methodology can potentially be tested to fine-tune fungicide application timing and in-season A. rolfsii management strategies. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
- Santosh Sanjel
- North Florida Research and Education Center, University of Florida, Quincy, FL
- Plant Pathology Department, University of Florida, Gainesville, FL
| | - Victor Guerra
- North Florida Research and Education Center, University of Florida, Quincy, FL
- Department of Soil, Water and Ecosystem Sciences, University of Florida, Gainesville, FL
| | - Ramdeo Seepaul
- North Florida Research and Education Center, University of Florida, Quincy, FL
- Agronomy Department, University of Florida, Gainesville, FL
| | - Cheryl Mackowiak
- North Florida Research and Education Center, University of Florida, Quincy, FL
- Department of Soil, Water and Ecosystem Sciences, University of Florida, Gainesville, FL
| | - Zamir K Punja
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Nicholas Dufault
- Plant Pathology Department, University of Florida, Gainesville, FL
| | - Barry Tillman
- Agronomy Department, University of Florida, Gainesville, FL
- North Florida Research and Education Center, University of Florida, Marianna, FL
| | - Kent J Bradford
- Department of Plant Sciences, University of California, Davis, CA
| | - Ian M Small
- North Florida Research and Education Center, University of Florida, Quincy, FL
- Plant Pathology Department, University of Florida, Gainesville, FL
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Allen PS, Finch-Boekweg H, Meyer SE. A proposed mechanism for high pathogen-caused mortality in the seed bank of an invasive annual grass. FUNGAL ECOL 2018. [DOI: 10.1016/j.funeco.2018.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Finch-Boekweg H, Gardner JS, Allen PS, Geary B. Postdispersal Infection and Disease Development of Pyrenophora semeniperda in Bromus tectorum Seeds. PHYTOPATHOLOGY 2016; 106:236-243. [PMID: 26645644 DOI: 10.1094/phyto-09-15-0229-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The Ascomycete fungus, Pyrenophora semeniperda, attacks a broad range of cool-season grasses. While leaf and predispersal infection of seeds (i.e., florets containing caryopses) have been previously characterized, little is known about the pathogenesis of mature seeds following dispersal. In this study, we examined infection and disease development of P. semeniperda on dormant seeds of Bromus tectorum. Inoculated seeds were hydrated at 20°C for up to 28 days. Disease development was characterized using scanning electron and light microscopy. P. semeniperda conidia germinated on the seed surface within 5 to 8 h. Hyphae grew on the seed surface and produced extracellular mucilage that eventually covered the seed. Appressoria formed on the ends of hyphae and penetrated through the lemma and palea, stomatal openings, and broken trichomes. The fungus then catabolized the endosperm, resulting in a visible cavity by 8 days. Pathogenesis of the embryo was associated with progressive loss of cell integrity and proliferation of mycelium. Beginning at approximately day 11, one to several stromata (approximately 150 μm in diameter and up to 4 mm in length) emerged through the lemma and palea. Degradation of embryo tissue was completed near 14 days. Conidiophores produced conidia between 21 and 28 days and often exhibited "Y-shaped" branching. This characterization of disease development corrects previous reports which concluded that P. semeniperda is only a weak seed pathogen with infection limited to the outermost seed tissues. In addition, the time required for disease development explains why infected dormant or slow-germinating seeds are most likely to experience mortality.
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Affiliation(s)
- Heather Finch-Boekweg
- First, third, and fourth authors: Brigham Young University, Department of Plant and Wildlife Sciences, Provo, UT 84602; and second author: Brigham Young University, Department of Biology, Provo, UT 84602
| | - John S Gardner
- First, third, and fourth authors: Brigham Young University, Department of Plant and Wildlife Sciences, Provo, UT 84602; and second author: Brigham Young University, Department of Biology, Provo, UT 84602
| | - Phil S Allen
- First, third, and fourth authors: Brigham Young University, Department of Plant and Wildlife Sciences, Provo, UT 84602; and second author: Brigham Young University, Department of Biology, Provo, UT 84602
| | - Brad Geary
- First, third, and fourth authors: Brigham Young University, Department of Plant and Wildlife Sciences, Provo, UT 84602; and second author: Brigham Young University, Department of Biology, Provo, UT 84602
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