Host-plant resistance to Pseudomonas solanacearum in tomato germplasm

Seedlings of two hundred and thirty-three accessions of the tomato collection maintained at the Centro Agronómico Tropical de Investigación y Enseñanza, Turrialba, Costa Rica (CATIE) and 7 cultivars used as controls were evaluated for host-plant resistance to 4 virulent strains of Pseudomonas solanacearum representing race 1 biovars 1 and 3. In general, biovar 3 strains wilted seedlings faster than biovar 1 strains but, after 20 days post-inoculation, no significant differences were noted in susceptible control ratings. Significant differences for disease index were noted, but no line with complete resistance was found. For the USA biovar 1 strain UW-25, only 5 accessions, CATIE 17331, 17334, 17349, 17739, 17740, and 2 of the control cultivars, Hawaii 7998 and UC-82B showed some degree of resistance. Conversely, both the frequency and the degree of resistance were high for Costa Rican biovar 1 strain UW-256. For biovar 3, the Costa Rican strain UW-255 was more virulent than the Peruvian strain UW-130. Eight CATIE accessions, 5539, 17331, 17333, 17334, 17345, 17349, 17742, and MIP-CH1, were as resistant as the resistant control Hawaii 7998 to 3 strains and accession 17740 was as resistant as Hawaii 7998 to all 4 strains.Journal Paper No. J-16011 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 3123.