Resistance to Gummy Stem Blight in Watermelon

Gabriele Gusmini, Todd C. Wehner, and Gerald J. Holmes


The purpose of this research project is:

  • to develop methods for evaluation of watermelon for resistance to gummy stem blight
  • to use those methods to screen the watermelon germplasm collection in comparison with commercial cultivars and resistant cucumbers
  • to calculate inheritance for watermelon resistance to bummy stem blight
  • to characterize Molecular Markers to tag genes for resistance
  • to breed resistant cultigens with commercial cultivars to make them resistant to gummy stem blight

So far we have developed a reliable screening method and we are developing a faster method based on inoculation of detached leaves only, we have finished the screening of 1274 PI Accessions from USDA Germplasm Collection, which involved multiple replications and years (from 1998 through 2001) in field and greenhouse.

We have already done P, F1, F2, BC1, and BC2 generations for the inheritance study and we are preparing the F3 generation for inheritance study and Molecular Markers.

The inheritance study and Molecular Markers experiment will be finished until Spring 2003 and resistant varieties might be released until 2005.


  • Gabriele Gusmini, MS Candidate
  • Todd C. Wehner, Professor, Horticultural Science
  • Gerald J. Holmes, Professor, Plant Pathology


  • Collect watermelon cultigens for use in screening
  • Collect isolates of GSB for methods development
  • Develop a method for screening the germplasm
  • Screen the germplasm for resistance to GSB
  • Determine inheritance in resistant x susceptible crosses
  • Develop elite inbred lines with high resistance to GSB


Research from this project will provide effective screening methods for use by seed company personnel in testing their cultivars for resistance to GSB. More important, resistant accessions identified could be used in breeding programs to develop improved watermelon cultivars. Resistance to GSB would provide growers with protection against loss by this disease, which is difficult to control, and requires multiple applications of fungicides during crop production.