Effect of Temperature, Dew Period, and Inoculum Density on Blight of Safflower Caused by Alternaria carthami. Cheryl F. McRae, CSIRO Centre for Irrigation Research, Private Mail Bag, Griffith, NSW 2680, Australia. E. K. S. Harrigan, CSIRO Centre for Irrigation Research, Private Mail Bag, Griffith, NSW 2680, Australia, and J. F. Brown, Department of Botany, University of New England, Armidale, NSW 2351, Australia. Plant Dis. 68:408-410. Accepted for publication 29 November 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-408.

The optimum temperature for expression of Alternaria blight symptoms on safflower (cultivar Gila) was 25 C. Frequency of stomatal penetration of leaf surfaces by germ tubes of A. carthami was greatest at 30 C. The percentage of safflower leaf area expressing blight symptoms increased as the length of the dew period and the inoculum density increased. Disease assessment keys based on the percentage of leaf or bract tissue showing symptoms of blight were developed to make quantitative disease assessments. A technique used to screen safflower cultivars for resistance to blight caused by A. carthami was also developed using the above results. Safflower seedlings were inoculated in a plastic tent with an inoculum density of 25 × 10⁴ propagules of A. carthami per milliliter and incubated at 25 C for 24 hr.

Keyword(s): Carthamus tinctorius.