Contrasting Properties of Flag Leaf Greenness in Ancient Wheat Species and Modern Bread Wheat

Abstract

A genotype with an ability to retain green leaf area for longer than an ordinary genotype is called a 'stay-green' phenotype. Such phenotypes may be able to assimilate more carbon during the post-anthesis grainfilling period. A field experiment was conducted to study genotypic differences of stay-green properties of ten genotypes belong to three ancient wheat species (Einkorn, Emmer and Spelt) and bread wheat in 2012 and another field experiment was conducted to identify the effect of nitrogen fertilizer on stay-green properties of the same genotypes in 2014 at University of Nottingham farms, UK. Flag leaf greenness was measured as visual greenness score and SPAD values in both experiments while NDVI was recorded only in 2014. Visual greenness score was plotted against thermal time (the base temperature at anthesis ℃) using a four-parameter logistic model to calculate green area duration and thermal time at maximum senescence rate. Aboveground biomass, grain yield and plant nitrogen uptake (excluding roots) were recorded at harvest. Genotypic variation was observed for all measured parametersin 2012 where the delayed onset of flag leaf senescence, slow senescence rate and prolonged leaf greenness were observed in Spelt cultivar Oberkulmer. Further, measured parameters were positively influenced by the increased level of nitrogen fertilizer in 2014. Above ground biomass was high in Spelt followed by Emmer, Bread Wheat and Einkorn genotypes at maturity. However, the highest grain yield was recorded in bread wheat genotypes compared to others suggesting its ability to convert more biomass towards the grain production. Green area duration was associated with aboveground biomass and plant nitrogen uptake in 2012. Therefore, favourable stay-green traits in Spelt, associated with N uptake, could be introduced to bread wheat through breeding programs in the future.