Developing a greenhouse protocol for evaluating resistance to Corynespora cassiicola in cotton

• Published in: Plant disease
• Main Authors: Moore, Carly, Sharma, Nancy, Bowen, Kira L, Koebernick, Jenny
• Format: Journal Article
• Language: English
• Published: United States 01.09.2021
• Subjects: cultivar/resistance; Disease management; Techniques; Epidemiology; Subject Areas
• ISSN: 0191-2917
• DOI: 10.1094/PDIS-08-20-1675-RE

Target spot, caused by , has re-emerged as a disease of economic importance in cotton ( L.) in the southeastern U.S. While this pathogen affects other economically important crops, relatively little is known about on cotton, especially with regard to conditions conducive for disease development and sources of genetic resistance. Therefore, in order to more efficiently screen cotton genotypes for resistance, a greenhouse protocol is needed. Optimum temperature and conducive leaf wetness duration were determined in growth chamber trials. Temperature range for disease onset as well as greatest lesion counts occurred between 20 and 28°C. Generally, with ≥ 24 h leaf wetness at these temperatures, disease onset was noted as rapidly as 1 day after inoculation on a cultivar that was previously determined to be susceptible to target spot. A mist irrigation system was used to maintain prolonged periods of leaf wetness in the greenhouse. In greenhouse trials, inoculation of cotyledons with 4 × 104 conidia/ml allowed differentiation of five selected genotypes with disease reactions that reflected their field rankings. The current protocol will be useful for evaluating cotton breeding lines for resistance to target spot.