Wheat's wild relatives vary in their response to nitrogen and ozone

Abstract

The wild relatives of bread wheat (Triticum aestivum) are valued by plant breeders for their genetic diversity. However, increasing levels of nitrogen (N) deposition and ground-level ozone (O 3 ) 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 O 3 . 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 O 3 (100 ppb for 21 days), alone and in combination. Measurements included root, shoot and seed biomass, and electrolyte ratios. The O 3 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 O 3. Both T. aestivum 'Cadenza' and T. dicoccoides produced immature seed heads, with the cultivar's seed head biomass reduced in response to O 3 and N + O 3 while that of T. dicoccoides was largely unaffected. These data suggest that all four wild relatives are likely to be affected when N and O 3 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 O 3 sensitivity.

Ozone Tolerance Found in Aegilops tauschii and Primary Synthetic Hexaploid Wheat

“…This is contrary to previous assessments of the ozone sensitivity of Ae. tauschii using young plants in a short ozone exposure during the vegetative stage [32,33]. The previous studies suggested that Ae.…”

“…Assessments of the ozone sensitivity of some of the close wild relatives of wheat have been made previously in short term experiments [32,33], with young plants (3–6 weeks old) receiving 3 weeks of ozone fumigation at 100 ppb concentrations. Ae.…”

“…Assessments of tetraploid wheats, Triticum turgidum ssp. durum [32] and T. dicoccoides [33] suggested they had greater ozone tolerance.…”

Soil pH drives poplar rhizosphere soil microbial community responses to ozone pollution and nitrogen addition

“…N fertilisation can profoundly alter plant growth, physiology, and productivity, all of which may shape the associated soil microbial community (Eastman et al, 2021; Zhang et al, 2018). Prior studies of O 3 × N interactions have primarily focused on aboveground effects and have yielded contradictory results, with some authors having reported that N addition can reverse the negative impact of O 3 exposure (Handley & Grulke, 2008; Mills et al, 2016), whereas others observed the opposite effect (Azuchi et al, 2014; Brewster et al, 2018) or detected no relationship between these variables (Feng, Shang, Li, et al, 2019; Harmens et al, 2017; Li et al, 2020). How soil microbial communities respond to O 3 and N addition thus remains to be clarified, and as such, further analyses of ecosystem responses and O 3 pollution feedback in an N‐enriched biosphere are warranted.…”