Assessing the genetic relatedness of higher ozone sensitivity of modern wheat to its wild and cultivated progenitors/relatives

Abstract Modern wheat (Triticum aestivum L.) is one of the most ozone (O 3 )-sensitive crops. However, little is known about its genetic background of O 3 sensitivity, which is fundamental for breeding O 3 -resistant cultivars. Wild and cultivated species of winter wheat including donors of the A, B and D genomes of T. aestivum were exposed to 100 ppb O 3 or charcoal-filtered air in open top chambers for 21 d. Responses to O 3 were assessed by visible O 3 injury, gas exchange, chlorophyll fluorescence, relative growth rate, and biomass accumulation. Ozone significantly decreased lightsaturated net photosynthetic rate (237%) and instantaneous transpiration efficiency (242%), but increased stomatal conductance (+11%) and intercellular CO 2 concentration (+11%). Elevated O 3 depressed ground fluorescence (28%), maximum fluorescence (226%), variable fluorescence (231%), and maximum photochemical efficiency (27%). Ozone also decreased relative growth rate and the allometric coefficient, which finally reduced total biomass accumulation (254%), but to a greater extent in roots (277%) than in the shoot (244%). Winter wheat exhibited significant interspecies variation in the impacts of elevated O 3 on photosynthesis and growth. Primitive cultivated wheat demonstrated the highest relative O 3 tolerance followed by modern wheat and wild wheat showed the lowest. Among the genome donors of modern wheat, Aegilops tauschii (DD) behaved as the most O 3 -sensitive followed by T. monococcum (AA) and Triticum turgidum ssp. durum (AABB) appeared to be the most O 3 -tolerant. It was concluded that the higher O 3 sensitivity of modern wheat was attributed to the increased O 3 sensitivity of Aegilops tauschii (DD), but not to Triticum turgidum ssp. durum (AABB) during speciation