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Three commercial planting media (Sunshine Mix#1, Sunshine Mix#5, and Metro Mix 360) were compared with the standard soil mixture prepared at New Mexico State Univ. for their effectiveness in differentiating Verticillium wilt—resistant and susceptible accessions of chile (Capsicum annuum L.) Each medium was infested with Verticillium dahliae Kleb. microsclerotia and planted with the resistant and susceptible accessions. When susceptible populations exhibited severe symptoms, individual plants were rated for disease severity (1 = no symptoms to 9 = death). Mean disease severities of populations differed among planting media, and, regardless of medium, resistant and susceptible populations were readily differentiated. Mean disease severities of plants grown in Sunshine Mix #1 and Sunshine Mix #5 differed from those grown in the standard University soil mix, but all media provided reliable screening tests. Mean disease severities of plants grown in Metro Mix 360 were most similar to those of plants grown in the University mix. Furthermore, greater differentiation was apparent between resistant and susceptible accessions in Metro Mix 360 than in accessions grown in the University medium.
Two studies were performed to evaluate techniques for screening verticillium wilt of Capsicum annuum L. The first study tested inoculation methods. The original method involved mixing the inoculum with planting medium in a cement mixer for 1 h. Seeds then were planted in the infested medium. In the new technique, inoculum is poured directly into the row, and seeds are placed directly on top of the inoculum. Inoculum levels of 2000 and 1000 mcrosclerotia/g of soil were tested in the new “in-row” method. The disease severity of the “in-row” plants was significantly less than the plants inoculated by the original method. A significant difference remained between resistant and susceptible lines. There was no difference between inoculum levels. The second study compared three commercial planting media to the standard soil used in previous screenings. Disease severity did not differ among media, and all media showed significant differences between resistant and susceptible C. annuum lines.