Evaluation location: North Carolina, United States
Accessions of watermelon were tested for Gummy stem blight (GSB) resistance. GSB is caused by
Didymella bryoniae (Auersw.) Rehm [=
Mycosphaerella citrullina (C.O.Sm.) Gross. and
Mycosphaerella melonis (Pass) Chiu & Walker]. The resistant check was PI 189225 and the susceptible check was 'Charleston Gray'. Field and greenhouse studies were conducted from 1998-2001.
The most resistant cultigens were chosen as having a low mean disease severity rating (x<4.0) and a low standard deviation. The most susceptible cultigens were chosen as having a high mean disease severity rating (x>6.0) and a low standard deviation. PI 189225 and PI 271778 were previously reported sources of resistance (Sowell and Pointer, Plant Disease Reporter 46:883-885. 1962. 59:413-415. 1975). Cultigens more resistant than PI 189225 and PI 271778 both in the field and greenhouse tests under heavy artificial inoculation were assumed to be more adapted to survive natural epidemics of gummy stem blight. Therefore, data are presented for mean disease resistance for all accessions more resistant than PI 189225 (mean = 3.8, standard deviation = 1.2), the most resistant accession previously known. Including PI 189225, there were 60 accessions that had some level of resistance. PI 279461, PI 482379, PI 254744, PI 526233, PI 482276, PI 271771, PI 164248, PI 244019, PI 296332, and PI 490383 were selected as the most resistant cultigens.
View the disease assessment scale in an Excel Spreadsheet or as an HTML webpage. View summary statistics in an Excel Spreadsheet or as an HTML webpage.