Differential ozone responses of selected winter wheat genotypes

Ozone (O 3 ) air pollution and the emerging races of stem rust, caused by Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn. ( Pgt ), continue to pose severe threats to global wheat production and food security. However, small grain crops tolerant to both abiotic and biotic stresses remain limited. The identification of potential wheat breeding material showing combined differential rust resistance and O 3 tolerance is a key step for developing resilient wheat varieties. We investigated the visible O 3 symptom responses of 31 key historic and current genotypes of wheat, barley, oat and triticale in continuous stirred-tank reactors (CSTRs) with four O 3 treatments (sub-ambient O 3 , 50, 75 or 100 ppb for 8 h d −1 ) at early growth stage. To further evaluate the impact of O 3 on yield production, we examined for two consecutive years genotypes exhibiting contrasting O 3 sensitivity in open-top chambers (OTCs). From the O 3 foliar injury screening results, the overall O 3 sensitivity among the tested cereals was spring wheat > winter wheat = winter oat > winter triticale > winter barley. The tested varieties of soft red winter wheat were more tolerant than the hard red winter wheat. Among the soft red winter wheat breeding line, MD01W28–08–11 exhibited exceptional tolerance to O 3 with negligible symptoms and sustained or increased grain yield under elevated O 3 concentrations applied during the post-heading stage in open top chambers. In contrast, soft red winter wheat cultivar, ‘Coker 9553’ showed significantly higher O 3 sensitivity in terms of visible symptoms and yield loss. Our results demonstrated that spring wheat is more susceptible to O 3 than winter wheat. This study further showed the soft red winter wheat class is more tolerant to O 3 than the hard red winter wheat class. Among the tested soft red winter wheat varieties, the MD01W28–08–11 breeding line exhibited exceptional O 3 tolerance, whereas ‘Coker 9553’ was sensitive to O 3 . Given the contrasting sensitivity to both elevated O 3 and rust disease, MD01W28–08–11 (O 3 -tolerant, Pgt -resistant) and ‘Coker 9553’ (O 3 -sensitive, Pgt -susceptible) provide excellent materials for breeding programs to improve stress tolerance as well as studies on the interaction of O 3 air pollution and rust diseases. • Foliar injury used as a screening tool to assess O 3 effects on cereals. • Wheat, oat, barley and triticale genotypes exhibited difference in O 3 sensitivity. • Soft red winter wheats are more tolerant to O 3 than hard red winter wheats. • MD01W28–08–11 wheat breeding line exhibited excellent O 3 tolerance. • Wheat genotypes were identified for breeding rust and O 3 resilient wheats.