Effects of Thinopyrum ponticum chromosome segments transferred into durum wheat on yield components and related morpho-physiological traits in Mediterranean rain-fed conditions

To verify previous results obtained on spaced plants regarding positive effects on yield-related traits of Thinopyrum ponticum chromosomal segments transferred into durum wheat, field plot trials were carried out over two years in Central Italy. Three durum wheat-Th. ponticum near isogenic recombinant lines (NIRLs), possessing 23%, 28% and 40% of their distal 7AL arm replaced by alien 7AgL chromatin, respectively, were included in the study. These lines underwent detailed phenotyping of more than 30 agronomic, physiological and qualitative traits, involving several novel traits at different developmental stages. Significant positive effects of defined 7AgL sub-regions on grain and tiller number and flag leaf dimensions, were confirmed over the two seasons, but also positive impacts on chlorophyll content and length of some phenological phases were identified. Overall, in spite of rather different weather conditions in the two seasons analysed, grain and biomass yield of all three NIRLs were 3–11% higher than their respective controls, while maintaining grain protein content higher than 15% across years in the presence of all 7AgL segments. Comparative analysis supported previous evidence that the NIRL with 28% 7AgL is the most promising for breeding exploitation, as in its 5% most proximal 7AgL portion gene(s)/QTL(s) enhancing various yield-contributing traits were located, including productive tiller number (+20%), flag leaf width and area (+8%), chlorophyll content at late grain filling (+15%) and booting-to-anthesis phases (+22%). These results suggest that mechanism(s) underlying the positive effects on yield are likely to be associated with the establishment of photosynthetically active canopy in interaction with effective biomass partitioning and, to some extent, phenology.