2006. Amphiploids of perennial Helianthus species x cultivated sunflower possess valuable genes for resistance to Sclerotinia stem and head rot

Field evaluation of Sclerotinia stem and head rot resistance using artificial inoculation was conducted using interspecific amphiploids of wild perennials Helianthus grosseserratus, H. hirsutus, H. maximiliani, H. nuttallii, H. strumosus crossed with P21, intercrossed amphiploids involving H. divaracatus and H. grossesserratus, and BC1F1 of an amphiploid involving H. strumosus. All the amphiploids had better stem rot resistance than the most stem rot tolerant check HA 410. Due to the late flowering of most amphiploids, head rot resistance was observed only in an amphiploid of H. nuttallii x P21, which segregated 11 resistant and 16 susceptible plants, compared to all 17 plants of the tolerant check HA 441 being susceptible. These amphiploids provide unique resistance genes for the development of germplasm superior to HA 410 and HA 441 for stem rot and head rot resistance, respectively