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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #314570
Title: Breeding and genetics of lettuce against race 2 of Verticillium wilt

Author
item SANDOYA, GERMAN - University Of California
item MICHELMORE, RICHARD - University Of California
item SUBBARAO, KRISHNA - University Of California
item Hayes, Ryan

Submitted to: Eucarpia Conference on Lettuce and Leafy Vegetables
Publication Type: Abstract Only
Publication Acceptance Date: 2/18/2015
Publication Date: 4/14/2015
Citation: Sandoya, G., Michelmore, R., Subbarao, K.V., Hayes, R.J. 2015. Breeding and genetics of lettuce against race 2 of Verticillium wilt. EUCARPIA Leafy Vegetables Congress, April 14-17, 2015, San Pedro del Pinatar, Spain.

Interpretive Summary:

Technical Abstract: Verticillium wilt, caused by the soil-borne fungus Verticillium dahliae, is a destructive disease of lettuce in California. Verticillium resistance 1 (Vr1) confers resistance to race 1 isolates but is defeated by race 2 isolates, which are predicted to increase in prevalence. Three Plant Introductions (PI) with partial resistance to race 2 were intercrossed with each other and a susceptible cultivar to determine the inheritance of resistance to race 2. Ninety-nine F3 families from PI 171674 × PI 204707, their parents, and the susceptible check ‘Salinas’ were inoculated with race 2 and evaluated for disease incidence (DI), disease severity (DS), foliar symptoms (FS) and days to flowering (DF). The experiment was conducted twice. F3 family means were quantitatively distributed, indicative of segregation for all traits. F3 family means ranged from 7 to 67% for DI, 0.2 to 3 for DS, 6 to 65% for FS, and 91 to 155 for DF. PI 171674 and PI 204707 significantly differed from each other and ‘Salinas’ with 17, 52 and 70% for DI, 0.8, 2.3 and 3.4 for DS, 13, 30 and 51% for FS, and 158, 108 and 178 for DFF, respectively. The segregation and high resistance found for this population is useful for identifying QTLs and breeding resistant cultivars. A population of 99 F3 families from Salinas × PI 169511 was evaluated in one greenhouse experiment and no significant differences were found for DI, DS, or FS. To identify better sources of race 2 resistance, 98 and 34 cultivars were inoculated in two replicated greenhouse experiments. PI 358038 had a median DI of 0% in both experiments with a maximum of 20%, while susceptible ‘Salinas’ had median DI of 20% and 65% with maximums of 25 and 100%, respectively. Complete resistance to race 2 has not been observed to date.