Increasing Temperature Reduces Wheat Resistance Mediated by Major Resistance Genes to Mayetiola destructor (Diptera: Cecidomyiidae).

Mayetiola destructor (Say) (Diptera: Cecidomyiidae) is a destructive pest of wheat and is mainly controlled by deploying resistant cultivars. Unfortunately, wheat resistance to Hessian fly is often lost when temperatures rise to a certain level. This study analyzed temperature sensitivity of 20 wheat cultivars that contain different resistance (R) genes. The lowest temperatures at which the percentage of resistant plants fell below 50% in an assay were 18°C for 'D6647 H17' (921680D1-7) (containing the R gene H17), 20°C for 'Redland' (H18), 22°C for '84702B14-1-3-4-3' (H19), 24°C for 'Carol' (H3) and 'Sincape90' (H29), 26°C for 'Erin' (H5), 'Jori 13' (H20), and 'PI59190' (H28), 28°C for 'Joy' (H10), 'KS99WGRC42' (Hdic), 'Karen' (H11), 'Caldwell' (H6), and 'Seneca' (H7H8), 30°C for 'KS85WGRC01' (H22) and 'KS92WGRC20' (H25), 32°C for 'Molly' (H13), and 34°C for 'Iris' (H9). The three cultivars 'H32 Synthetic' (H32), '81602C5-3-3-8-1' (H15), and 'KS93WGRC26' (H26) exhibited the most resistance to temperature increases. The percentages of resistant plants remained above 50% at 36°C for these three cultivars, the highest temperature that can be tested without significantly damaging wheat plant growth. The temperature sensitivity of R gene-mediated fly resistance is also strongly affected by genetic background of wheat cultivars that contain a specific R gene. Our data should provide useful information for breeding wheat resistance to control Hessian fly damage in different regions based on historic temperature data.