Cucurbit Genetics Cooperative Report 1:24 (article 23) 1978
Watermelon: Breeding for Resistance to Mycosphaerella citrullina and Colletotrichum lagenarium
J. D. Norton
Auburn University Agricultural Experiment Station, Auburn, AL 36830
Severe crop losses and reduced yields of melons have resulted from gummy stem blight Mycosphaerella citrullina in certain fields in Alabama. Although the damage seemed to be more widespread in the Gulf Coast area, there have been frequent reports of damage in central and northern Alabama.
Plant introductions, PI 189225 and PI 271778, were recently classified as resistant to Mycosphaerella citrullina.1
A planting of PI 189225 and PI 271778 and desirable cultivars was made in the greenhouse in the winter of 1969-1970 to permit crosses of the resistant and susceptible material. A backcrossing and screening program is being followed to incorporate resistance to M. citrullina into commercial types. High resistance in PI 189225 and moderate resistance in PI 271778 are due to two independent and different recessive gene pairs.
Advanced breeding lines with resistance to M. citrullina and high quality fruit were available for evaluation in the Southern Cooperative Watermelon Variety Trials in 1977. A replicated test of six of these lines in 1976 indicated that Auburn breeding lines 1, 3, and 5 are worthy of further evaluation for possible release.
An active breeding program to develop breeding lines resistant to Colletotrichum lagenarium (Race 2) is in progress. PI 189225 and PI 271778 are being used as sources of resistance.
Resistance to C. lagenarium is present in a number of advanced breeding lines from the M. citrullina breeding program.
1 G. B. Sowell, Jr., Research Pathologist, US Department of Agriculture, S.E. Regional Plant Introduction Station, Experiment, Georgia.