title: Evaluation of Aegilops tauschii and Aegilops speltoides for acquired thermotolerance: Implications in wheat breeding programmes.
abstract: Severe and frequent heat waves are predicted in the near future having dramatic and far-reaching ecological and social impact. The aim of this study was to examine acquired thermotolerance of two Aegilops species: Aegilops tauschii and Aegilops speltoides and study their potential adaptive mechanisms. The effect of two episodes of high heat stress (45 °C/12 h) with a day of recovery period was investigated on their physiology. As compared to A. speltoides, A. tauschii suffered less inhibition of photosystem II efficiency and net photosynthetic rate (Pn). Although A. tauschii showed nearly complete recovery of PSII, the adverse effect was more pronounced in A. speltoides. Measurement of the minimum fluorescence (Fo) versus temperature curves revealed a higher inflection temperature of Fo for A. tauschii than A. speltoides, reflecting greater thermo stability of the photosynthetic apparatus. Absorbed light energy distribution revealed that A. speltoides showed increased steady state fluorescence and a lower absorbed light allocated to photosynthetic chemistry (ɸPSII) relative to A. tauschii. However, A. tauschii showed higher ability to scavenge free radicals as compared to A. speltoides. This was further validated by higher expression of ascorbate peroxidase gene. These results suggest that A. tauschii showed faster recovery and a better thermostability of its photosynthetic apparatus under severe stress conditions along with a better regulation of energy channeling of PSII complexes to minimize oxidative damage and thus retains greater capability of carbon assimilation. These factors aid in imparting a greater heat tolerance to A. tauschii as compared to A. speltoides and thus make it a better candidate for alien species introgression in wheat breeding programs for thermotolerance in wheat.
authors.affiliation: Department of Plant Molecular Biology, University of Delhi, South Campus, Benito Juarez Road, Dhaula Kuan, New Delhi 110 021, India.
authors.forename: Suboot
authors.initials: S
authors.lastname: Hairat
authors.affiliation: Department of Plant Molecular Biology, University of Delhi, South Campus, Benito Juarez Road, Dhaula Kuan, New Delhi 110 021, India. Electronic address: param@genomeindia.org.
authors.forename: Paramjit
authors.initials: P
authors.lastname: Khurana
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D018869:Heat-Shock Response / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D000069600:Plant Breeding; D006109:Poaceae / Q000201:enzymology*
chemical_list: D045332:Photosystem II Protein Complex
keywords: Aegilops; Chlorophyll content; Gas exchange; Heat; Non photochemical quenching; Oxidative stress; Photosynthetic efficiency