Differential ozone responses of selected winter wheat genotypes

Context: Ozone (O3) 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.

Objective: The identification of potential wheat breeding material showing combined differential rust resistance and O3 tolerance is a key step for developing resilient wheat varieties.

Methods: Authors investigated the visible O3 symptom responses of 31 key historic and current genotypes of wheat, barley, oat and triticale in continuous stirred-tank reactors (CSTRs) with four O3 treatments (sub-ambient O3, 50, 75 or 100 ppb for 8 h d− 1) at early growth stage. To further evaluate the impact of O3 on yield production, authors examined for two consecutive years genotypes exhibiting contrasting O3 sensitivity in open-top chambers (OTCs).

Results: From the O3 foliar injury screening results, the overall O3 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 O3 with negligible symptoms and sustained or increased grain yield under elevated O3 concentrations applied during the post-heading stage in open top chambers. In contrast, soft red winter wheat cultivar, ‘Coker 9553’ showed significantly higher O3 sensitivity in terms of visible symptoms and yield loss.

Conclusions: These results demonstrated that spring wheat is more susceptible to O3 than winter wheat. This study further showed the soft red winter wheat class is more tolerant to O3 than the hard red winter wheat class. Among the tested soft red winter wheat varieties, the MD01W28–08–11 breeding line exhibited exceptional O3 tolerance, whereas ‘Coker 9553’ was sensitive to O3.

Implications: Given the contrasting sensitivity to both elevated O3 and rust disease, MD01W28–08–11 (O3-tolerant, Pgt-resistant) and ‘Coker 9553’ (O3-sensitive, Pgt-susceptible) provide excellent materials for breeding programs to improve stress tolerance as well as studies on the interaction of O3 air pollution and rust diseases