Photoperiodism in Eragrostis ter: Analysis of ontogeny and morphology in response to photoperiod

Background: The Ethiopian cereal teff (Eragrostis tef (Zuccagni) Trotter), traditionally grown under short days (11-13 h) (SD), is currently introduced into NW Europe where the early phases of the growing season are characterized by long days (15-17 h) (LD). This paper analyzes to what degree teff's ontogeny and morphology are day length sensitive. Methods: To analyze the day length response of teff considering panicle initiation, time to heading, number of phytomers, plant height and biomass, growth chamber and greenhouse experiments were conducted. In these experiments two Ethiopian cultivars, Gibe and Ziquala, and two cultivars from a Dutch breeding programme, Ayana and 04T19, were exposed to day lengths of 9, 10.5, 12, 13.5, 15, 16.5 and 18 h. Key results: The Ethiopian cultivars of teff showed a stronger photoperiod response than the Dutch cultivars. For example, time to heading for Ziquala was 88 d under LD but 37 d under SD whereas for Ayana it was 45d under LD and 29 d under SD. Time to heading could be described using a smooth logistic function consisting of four biologically interpretable parameters. Application of the same function to literature data of the short day plants: rice (Oryza saliva) and soya bean (Glycine max), and the long day plants: wheat (Triticum aestivum) and wild oat (Avena fatua) showed the broader applicability of the approach. Not only panicle initiation of teff, but also development and outgrowth of the panicle were influenced by photoperiod. Plant-to-plant variation in time to heading, the total number of phytomers per shoot, the number of elongated internodes and biomass were higher in LD than in SD treatments for all cultivars. Conclusions: This paper provides a detailed description and quantification of the response of teff to day length. The smooth logistic function presented is applicable not only for teff, but also for other short day (rice and soya bean) and long day (wheat and wild oat) species. We revealed, moreover, genetic variation in day length sensitivity, including a strain that showed almost day length neutral behaviour. The ample genetic variation between cultivars suggests there is a basis for breeding for high yielding cultivars for the northern latitudes. (C) 2011 Elsevier By. All rights reserved.