Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: April 19, 2005
Publication Date: April 20, 2005
Citation: Block, C.C. 2005. Evaluation of wild helianthus annuus for resistance to septoria leaf blight. Proceedings Sunflower Research Workshop. Available: http://www.sunflowernsa.com/research/research-workshop/documents/Block_Septoria_05.PDF Technical Abstract: The objectives of this study were to evaluate wild Helianthus annuus germplasm for Septoria leaf blight resistance, and to compare the frequency of resistance by geographic region of accession origin in the United States. One hundred twenty-eight wild H. annuus accessions were evaluated in field trials at Ames, IA during 2000 and 2001. The accessions were selected to represent seven broadly defined geographic regions of the U.S., including Texas (TX), Arizona-New Mexico (AZ-NM), California (CA), Kansas (KS), North and South Dakota (ND-SD), the Pacific Northwest (PNW) and Illinois (IL). Plants were rated visually on a 1-4 descriptive scale, with 1 corresponding to highly resistant plants. Eight plants were rated per plot and the average of four replicate plots per accession was calculated. Accessions from dry or desert-like environments were very susceptible, including all 39 accessions from the CA and PNW groups, 16 of 20 accessions from AZ-NM and 13 of 20 from the ND-SD group. A two-year average score of <2.25 was used to distinguish the most resistant accessions. This group of 21 accessions included nine from KS, seven from TX, four from IL, and one from SD. Resistance to Septoria leaf blight in the TX material was found in accessions along the Gulf coast. The coastal area was expected to be a source of leaf blight resistant germplasm because of its high rainfall and humidity. The equally good resistance of the eastern KS and western IL accessions was not expected. The resistance in KS and IL germplasm indicates that resistance would likely be found in Missouri and probably Iowa accessions as well. This study demonstrates that wild H. annuus germplasm contains potentially useful resistance genes that could be used to improve cultivated sunflowers in parts of the world where Septoria leaf blight is a problem.