Quantitative Trait Loci for Chlorophyll Content in Durum Wheat

Leaf photosynthesis is the component of canopy photosynthesis that accounts for most of the variation in biomass production and yield. Leaf photosynthesis, leaf nitrogen content and stress conditions in plants can be estimated from measurements of chlorophyll content. Soil Plant Analyzer Development (SPAD) measurements provide a useful screening criterion in breeding programs aimed at increasing the rate and duration of leaf photosynthesis. The aim of this work was to identify and map quantitative trait loci (QTL) for SPAD measurements in durum wheat (Triticum turgidum L. subsp. durum) under semiarid conditions. A doubled haploid population of 86 durum wheat lines developed from the cross ‘Strongfield’ x ‘Blackbird’ was studied in 2010 and 2011 field experiments. A portable chlorophyll meter (SPAD) recorded the chlorophyll content at anthesis (Zadoks scale 65) on the flag leaf of five plants taken at random. The analysis revealed putative SPAD quantitative trait loci on chromosomes 2B and 3B in both years. The QTL on chromosome 2B was found in the interval of the linked markers Xwmc474 to Xbarc55 explaining 9.7% and 15% of the total phenotypic variance in 2010 and 2011, respectively.  The chromosome 3B interval, Xcfd283 to Xwmc418, in 2010 explained 13.4% and in 2011 explained 14.2% of the total phenotypic variance. Our results provide a first step to identify candidate genes in durum wheat in semiarid conditions that may play an important role in increasing leaf photosynthesis by selection for elevated chlorophyll content loci.