Resistance to Tan Spot in a Synthetic Hexaploid Wheat Collection Measured in a Seedling Greenhouse Assay

Abstract

A collection synthetic hexaploid wheat accessions developed at the International Corn and Wheat Improvement Center (CIMMYT) was evaluated for seedling resistance to tan spot in a greenhouse assay. The causal organism of tan spot Pyrenophora trtitici-repentis is an ascomycete that over-seasons on wheat stubble and can cause up to 50% loss in yield in favorable environments. Seedlings planted in a randomized complete block design were inoculated with a chlorosis and necrosis producing isolate collected from Oklahoma and evaluated for percent leaf infection at the 3 to 5 leaf stage one week post-inoculation. Of the 94 synthetic hexaploid wheat accessions tested, 54% showed high resistance when compared to the resistant check, 'Red Chief'.. The visual percentage leaf area infection ratings were compared with digital ratings calculated with Assess software (APS Press, 2002). The visual ratings were highly correlated with the digital ratings validating the use of visual estimates of percentage leaf area infection for tan spot reaction. Synthetic hexaploid wheat is a potential source of resistance to tan spot. Resistance and susceptibility can be assessed using percentage leaf infection in a greenhouse assay.