Sooty blotch and flyspeck: Evaluation of remotely estimated weather inputs to disease-warning systems and delineation of fungal taxa closely grouping with Mycosphaerella madeirae

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Tatalovic, Nenad
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Mark L. Gleason
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Plant Pathology and Microbiology
The Department of Plant Pathology and Microbiology and the Department of Entomology officially merged as of September 1, 2022. The new department is known as the Department of Plant Pathology, Entomology, and Microbiology (PPEM). The overall mission of the Department is to benefit society through research, teaching, and extension activities that improve pest management and prevent disease. Collectively, the Department consists of about 100 faculty, staff, and students who are engaged in research, teaching, and extension activities that are central to the mission of the College of Agriculture and Life Sciences. The Department possesses state-of-the-art research and teaching facilities in the Advanced Research and Teaching Building and in Science II. In addition, research and extension activities are performed off-campus at the Field Extension Education Laboratory, the Horticulture Station, the Agriculture Engineering/Agronomy Farm, and several Research and Demonstration Farms located around the state. Furthermore, the Department houses the Plant and Insect Diagnostic Clinic, the Iowa Soybean Research Center, the Insect Zoo, and BugGuide. Several USDA-ARS scientists are also affiliated with the Department.
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Disease-warning systems are management tools that use information about the pathogen, host and/or environment to advise growers when to efficiently take management actions, such as fungicide sprays. This study examined usage of alternative weather information as inputs to disease-warning systems for control of sooty blotch and flyspeck (SBFS) of apple and watermelon anthracnose, as well as the morphology of isolates of the SBFS fungi that grouped with the Mycosphaerellaceae.

The first objective was to evaluate the effectiveness of alternative sources of weather data as inputs to disease-warning systems for sooty blotch and flyspeck (SBFS) on apple and watermelon anthracnose caused by Colletotrichum orbiculare (Berk & Mont.) Arx (1957) on watermelon in replicated field trials conducted in Iowa during 2006 to 2008. Leaf wetness duration (LWD) data estimated by commercial site-specific technology, or by model-based corrections of these estimates, were compared with measurements made by on-site sensors. In both warning systems, using remotely estimated and model-corrected LWD data resulted in disease levels that were similar or equal to those observed when using on-site measurements. Our study provides evidence that remotely estimated LWD data and model-corrected versions of these data may be used successfully in implementation of warning systems for SBFS on apple and anthracnose on watermelon.

The second objective was to examine the morphology and rDNA sequences of 124 isolates of SBFS fungi from Germany and the U.S. Parsimony analysis of the internal transcribed spacer (ITS) region of the rDNA grouped isolates into 14 clades. Molecular evidence coupled with morphology of representative isolates from each clade on preserved apple peels and on media indicated that there were 10 SBFS species among the isolates. Five putative species were placed in the anamorph genus Pseudocercosporella, and two putative species were placed in the anamorph genus Ramichloridium. Three putative species designated as sterile mycelia did not produce conidia. Parsimony analysis of the large subunit (LSU) region of rDNA placed all 10 putative species near Mycosphaerella madeirae with bootstrap support of 66%. The genus Mycosphaerella consists of several thousand species; our findings help to clarify taxonomic placement of these anamorph species of SBFS within the family Mycosphaerellaceae.

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Thu Jan 01 00:00:00 UTC 2009