Resistance of wild sunflower species to mild-stalk rot caused by Sclerotinia sclerotiorum

Keranka Zhecheva, Daniela Valkova, Ivan Kiryakov

Abstract: Sclerotinia seclerotiorum is a critical pathogen in sunflowers. Depending on the organs it attacks, the disease has three forms of manifestation - basal stalk rot, mid-stalk rot, and head rot. Identifying sources of resistance is paramount to the success of breeding programs in creating resistance to the pathogen. The aim of the present study was to determine the response of 29 wild specimens of Helianthus ssp. to the mid-stalk rot of S. sclerotiorum under field conditions. The accessions were inoculated by the STRAW-method with two pathogen isolates in the flowering growth stage. The response of the accessions was evaluated on a 9-degree scale, 14 days after inoculation, with a score of 1.0 to 5.0 being considered a highly resistant to moderately resistant phenotype, respectively. Nine of the studied accessions have moderately resistance to SS1914 isolate and 16 to SS1941 isolate. Moderately resistant to both isolates are 9 accessions, 7 of which are wild H. annuus and one each of H. petiolaris and H. praecox ssp. runyonii. Isolate SS1914 was more aggressive than isolate SS1941 to the studied accessions.

Keywords: mid-stalk rot resistance; S. sclerotiorum; wild Helianthus spp.

Date published: 2023-06-27