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* These authors contributed equally
Managing Fusarium wilt of watermelon requires knowledge of the pathogen races present. Here, we describe the root-dip, infested kernel seeding, and modified tray-dip inoculation methods to demonstrate their efficacy in race-typing of the pathogenic fungus Fusarium oxysporum f. sp niveum (Fon).
Fusarium wilt of watermelon (Citrullus lanatus), caused by Fusarium oxysporum f. sp. niveum (Fon), has reemerged as a major production constraint in the southeastern USA, especially in Florida. Deployment of integrated pest management strategies, such as race-specific resistant cultivars, requires information on the diversity and population density of the pathogen in growers' fields. Despite some progress in developing molecular diagnostic tools to identify pathogen isolates, race determination often requires bioassay approaches.
Race typing was conducted by root-dip inoculation, infested kernel seeding method, and the modified tray-dip method with each of the four watermelon differentials (Black Diamond, Charleston Grey, Calhoun Grey, Plant Introduction 296341-FR). Isolates are assigned a race designation by calculation of disease incidence five weeks after inoculation. If less than 33% of the plants for a particular cultivar were symptomatic, they were categorized as resistant. Those cultivars with incidence greater than 33% were regarded as susceptible. This paper describes three different methods of inoculation to ascertain race, root-dip, infested kernel, and modified tray-dip inoculation, whose applications vary according to the experimental design.
The soilborne fungi that make up the Fusarium oxysporum species complex (FOSC) are impactful hemibiotrophic plant pathogens that can cause serious disease and yield loss in a diverse range of crops1. Fusarium wilt of watermelon, caused by F. oxysporum f. sp. niveum (Fon), has been increasing in scope, incidence, and severity across the world in the last several decades2,3. In seedlings, the symptoms of Fusarium wilt often resemble damping-off. In older plants, the foliage becomes gray, chlorotic, and necrotic. Eventually, wilting of the plants progres....
1. Determining race by root-dip method (RDM)
These experiments help define the relative resistance of commonly grown cultivars (Table 1). This information can then be used to guide management recommendations based on local Fon populations. In other words, if race 0 or 1 is known to be present in a commercial field, then the farmer may be inclined to grow a "resistant" variety such as Calhoun Gray, Sunsugar, or equivalent. The results of the bioassays using all methods show that when the seedlings were infected with a Race 1 isolate, the Bla.......
Three methods of race typing have been presented. Each of these methods is best suited to particular questions and experimental conditions. The infested kernel inoculation method (soil infestation) is perhaps simpler and more straightforward, making it especially useful for the assessment of pathogenicity30. Using this method for simple race-typing is highly effective. However, applying the method to determine the resistance of a specific cultivar could be challenging, given that each plant may no.......
We would like to acknowledge Dr. Ali and the Plant Molecular Diagnostic Laboratory as well as Dr. Pingsheng Ji at the University of Georgia, whose leadership and support helped establish our Fon program.
....Name | Company | Catalog Number | Comments |
100% Fuller’s Earth | Sigma-Aldrich | F200-5KG | |
1 L glass Erlenmeyer Flask | PYREX | 4980-1L | |
15 mL falcon tubes | Fisher Scientific | 14-959-49B | |
50 mL graduated cylinder | Lab Safety Supply | 41121805 | |
50 mL Eppendorf Conical Tubes | Fisher Scientific | 05-413-921 | |
Aluminum foil wrap | Reynolds Wrap | 720 | |
Bleach | Walmart | 587192290 | |
Bunsen burner | Fisher Scientific | 03-391-301 | |
CaCO3 | sigma-Aldrich | 239216 | |
cell spreaders | Fisher Scientific | 08-100-11 | |
Cheesecloth | Lions Services, Inc | 8305-01-125-0725 | |
Clear plastic dishes | Visions Wave | 999RP6CLSS | ~15 cm diameter |
Clear vinyl tubing for mushroom bag clamps | Shroom Supply | 6" for small bag, 8" for medium bag, 10" for large bag | |
Cotton Balls | Fisherbrand | 22-456-885 | Sterile |
Ethanol | Fisher Chemical | A4094 | 100%, then combine with water to make 70% for use |
Flourescent Tube Lights | MaxLume | Model T5 | 2800 K Color Temperature, 24'' or 48'' long |
granulated agar | VWR International | 90000-786 | |
Hand-held Spray Bottle | Ability One | 24122002 | ~0.95 L |
hemacytometer | Fisher Scientific | 02-671-55A | Two chamber hemacytometer |
Lab trays | Fisher Scientific | 15-236-2A | |
Large, sealable plastic bags | Ziploc | 430805 | 38 cm x 38 cm |
Mister / watering can | Bar5F | B10H22 | |
Mushroom Bag Clamp | Shroom Supply | 6" for small bag, 8" for medium bag, 10" for large bag | |
Nitrile Gloves | Fisher Scientific | 19-130-1597D | |
Organic Rye Berries | Shroom Supply | 0.5 gallon or 25 lb bags | |
P1000 pipette and tips | Fisher Scientific | 14-388-100 | |
Petri dishes | Fisherbrand | FB0875713 | Round, 100 mm diameter, 15 mm height |
Planting media | Jolly Gardener | Pro-Line C/B | |
Plastic Pitcher | BrandTech | UX0600850 | 1 L or larger |
Plastic planting pots | Neo/SCI | 01-1177 | ~15 cm diameter and ~10 cm height |
Plastic, autoclave-safe bin | Thermo Scientific | UX0601022 | 3 L |
Quarter-strength potato dextrose agar media | Cole-Parmer | UX1420028 | Use powder in combination with recipe for QPDA |
Scientific Balance Scale, measuring in g | Ohaus | 30208458 | Any precise scale that can hold and measure 200g will work |
Size #4 cork bore | Cole-Parmer | NC9585352 | |
Small Mushroom grow bag | Shroom Supply | 0.5 micron filter, also comes in medium and large sizes | |
Soil trowel | Walmart | 563876946 | |
Styrofoam flats (6 x 12 cells) | Speedling | Model TR72A | |
Styrofoam flats (8 x 16 cells) | Speedling | Model TR128A | |
Syringe (5 or 10 mL) | fisher Scientific | 14-829-19C | |
Timer | Walmart | TM-01 | |
V8 Original 100% Vegetable Juice | Walmart | 564638212 | |
vortex | Fisher Scientific | 02-215-418 | |
Watermelon Seed - Black Diamond | Willhite Seed Inc | 17 | |
Watermelon Seed - Calhoun Gray | Holmes Seed Company | 4440 | |
Watermelon Seed - Charleston Gray | Bonnie Plants | 7.15339E+11 | |
Watermelon Seed - PI 296341-FR | Contact authors | Contact authors | |
Wheat Kernels (Maxie var.) (optional) | Alachua County Feed & Seed |
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