BREEDING FOR DISEASE MANAGEMENT IN TOMATOES

Public breeding for organic agriculture:
Screening horizontal resistance to Late blight in tomatoes

Port Townsend, WA - Late blight (LB) of tomato and potato, caused by the fungal pathogen Phytophthera infestans, is currently the most destructive disease of tomato in the Pacific Northwest. Tomato researchers have reported an increase in both the virulence and prevalence of many new genotypes of this pathogen.

The goal of this research is to quantify resistance to late blight by screening varieties previously identified as having moderate levels of blight resistance under conditions conducive to the spread of the fungus P. infestans. In 2004, twelve tomato accessions were planted at two different organic farm sites, and data was collected in these field trial evaluations.

Photo: Cull pile of unmarketable fruits with late blight symptoms
7-10 days after the initial disease outbreak.

For Matt Dillon's complete project report (12 pages), link to: dillon_04s20.pdf

• This experiment was successful in demonstrating that there exists tomato germplasm that has levels of resistance to a very pathogenic genotype of LB under field conditions.
• Resistance to late blight was found in both 'NC 03220' and in 'Stupice'. 'Juliet' was also resistant. While 'NC 03220' and 'Juliet' are late maturing in western Washington, 'Stupice' is well adapted to the Northwest's short growing season and would be an excellent population to select within for increased horizontal resistance (HR) and superior quality attributes.
• This experiment also successfully identified a range of materials that are resistant to early blight. Among the most resistant were 'NC 03220' and 'Juliet' which were also at the top for LB resistance. '

Principal investigator: Matthew Dillon, Organic Seed Alliance, Port Townsend, WA. tel. 360-385-7192 matthew@seedalliance.org

Co-investigators: John Navazio, Organic Seed Alliance; Kate Dean, Old Tarboo Farm, Quilcene, WA; Martha Rosemeyer, The Evergreen State College, Olympia, WA

Project locations: Old Tarboo Farm, Quilcene, WA and The Evergreen State College

OFRF support: $10,068, awarded spring 2004

Full project report: 12 pages, submitted December 2005. Available at ofrf.org.