The wild relatives of bread wheat (Triticum aestivum L.) are valued by plant
breeders for their genetic diversity. However, increasing levels of nitrogen
(N) deposition and ground-level ozone (O3) threaten plant biodiversity in
the Mediterranean and Near-East, a hotspot for many crop wild relatives.
Knowledge of the effect of these air pollutants in combination is still limited, but
early indications are that effects vary depending on the level of pollutants, and
on the sensitivity of the species to N and O3. This study examined the responses
of four important wheat wild relatives (Aegilops tauschii, Aegilops speltoides,
Triticum dicoccoides and Triticum monococcum) and one modern wheat cultivar
(T. aestivum ‘Cadenza’) to treatments of N (equivalent to 50 kg ha−1 year−1
ammonium nitrate) and O3 (100 ppb for 21 days), alone and in combination.
Measurements included root, shoot and seed biomass, and electrolyte ratios.
The O3 sensitivity of A. tauschii and T. aestivum ‘Cadenza’ were exacerbated
by the addition of N, while A. speltoides was found to be nitrophilous, with
N ameliorating the negative effect of O3. Both T. aestivum ‘Cadenza’ and T.
dicoccoides produced immature seed heads, with the cultivar’s seed head biomass reduced in response to O3 and N+O3 while that of T. dicoccoides was largely unaffected. These data suggest that all four wild relatives are likely to be affected when N and O3 air pollutants co-occur, and there in situ populations may therefore be at risk. Equally, the results of this study can inform use of their
beneficial traits by wheat breeders, and alert them to the inadvertent inclusion
of N and O3 sensitivity.