Watermelon
Crop Information
Watermelon Screening Method for Gummy Stem Blight Resistance
- by Gabriele Gusmini and Todd C. Wehner
- Department of Horticultural Science
- North Carolina State University
- Raleigh, NC 27695-7609
After running many experiments, we would recommend using
cultures grown for 2 to 3 weeks on potato dextrose agar
under artificial light for 12 hours per day, use of isolate
mixtures to ensure pathogenicity, constant reisolation of
new isolates from diseased plants in the field, suspension
of spores in water for spray application, a spore concentration
of 500,000 spores/ml, addition of surfactant to the suspension
([Tween 80] = 0.06 g/l), use of high relative humidity immediately
following inoculation (with the presence of free-standing
water on the leaves of test plants), and pre-inoculation
damage of the leaves. Environmental variation requires that
many plants, replications, seasons (spring, summer, fall),
years, and test types (field and greenhouse) be used to
evaluate resistance to gummy stem blight. If the objective
were to develop resistant inbreds, we would recommend an
experiment having 6 plants, 3 to 5 replications, 1 to 3
seasons (or planting dates), 1 year (for rapid progress),
and 2 test types.
Inoculum preparation
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|
|
Small scale production
of spores in Petri plates |
Large scale production
of spores in Nalgene boxes |
Spore suspension
ready for dilution and inoculation |
Types of humidity chambers for greenhouse
test
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|
|
Inexpensive and
temporary type |
Inexpensive and
semi-permanent type |
Expensive and
permanent type |
