Alternaria-Resistant Safflower

Alternaria Leaf Spot Identification

• The fungus Alternaria carthami causes Alternaria leaf spot in damp, rainy conditions, preventing safflower seeds from germinating and causing blight in seedlings. The fungus causes 1/2-inch-diameter brown spots on leaves. The spots begin low on the plants and appear higher as the growing season progresses, eventually affecting flower bracts and seed heads. The result may be entire crops of shriveled, discolored safflower seeds that are worthless for birdseed or oil.

First Alternaria-Resistant Variety

• American breeding of hybrid safflower cultivars that would be resistant to Alternaria began in Sidney, Montana, in the early 1960s. The effort led to several Alternaria-resistant cultivars, notably Carthamus tinctorius “Girard” in the late 1980s, and it is still planted with good yields.

Later Resistant Varieties

• Utah State University Extension reported information about three safflower varieties that had varying degrees of resistance or tolerance to Alternaria. Montola 2003, an oil hybrid, has moderate tolerance. Nutrasaff, with a high oil content, resists the disease better than other cultivars. Finch, developed for birdseed, is moderately tolerant. Montana State University released the MonDak High Oleic Safflower Oil variety, which has improved Alternaria resistance and yields better than Montola but has a lower oil content. Montana State's Cardinal High Linoleic Safflower Oil variety has improved resistance to Alternaria, yields better than Finch and has the white-hulled seeds preferred for birdseed. Centennial has very good yield but only moderate tolerance to the fungus. Hartman tolerates Alternaria and has fair yields. Oker tolerates the disease but yields poorly.

Seed Availability

• Although safflower varieties that resist or tolerate Alternaria are available, none are 100-percent guaranteed to resist the disease. Safflower seeds that are certified to be disease-free and seeds that were treated to prevent Alternaria are available.