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

We 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, we 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

Our 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.