Physiologic specialization of Puccinia triticina in Syria

Leaf rust, caused by Puccinia triticina Eriks., is one of the major diseases of wheat in Syria. Surveys of durum wheat fields were carried out in all durum wheat growing regions in Syria during  2010. A total of 120 samples of P. triticina were collected. Single pustules from each collection were multiplied on the susceptible cultivar Cham1. Eighty-five percent of the surveyed fields were infested with wheat leaf rust, the greatest rate recorded in Syria during the previous seven growing seasons (2003–09). Twenty physiologc races were identified using the North American system of nomenclature, and six groups of races were identified using the Unified System. Races varied in their frequency and virulence. Four races were recorded for the first time in Syria, including LBBT, PMRR, SCBK and TBRM. The most virulent races found in the study were TBRT, first recorded in Lebanon in 2008, and PMRR, followed by PBPT, TBLR, TBRM, TLRB, CBRT, and SBRN.  Some of the older races, such as CBRT which was first found in 2005 only in a few fields in Latakia  in Western Syria, were found in most regions sampled. The host resistance gene Lr24 was completely effective against all twenty physiologic races identified.  This gene is recommended for use  by wheat breeders to improve the resistance for leaf rust in new wheat cultivars

Systems responses to progressive water stress in durum wheat

Durum wheat is susceptible to terminal drought which can greatly decrease grain yield. Breeding to improve crop yield is hampered by inadequate knowledge of how the physiological and metabolic changes caused by drought are related to gene expression. To gain better insight into mechanisms defining resistance to water stress we studied the physiological and transcriptome responses of three durum breeding lines varying for yield stability under drought. Parents of a mapping population (Lahn x Cham1) and a recombinant inbred line (RIL2219) showed lowered flag leaf relative water content, water potential and photosynthesis when subjected to controlled water stress time transient experiments over a six-day period. RIL2219 lost less water and showed constitutively higher stomatal conductance, photosynthesis, transpiration, abscisic acid content and enhanced osmotic adjustment at equivalent leaf water compared to parents, thus defining a physiological strategy for high yield stability under water stress. Parallel analysis of the flag leaf transcriptome under stress uncovered global trends of early changes in regulatory pathways, reconfiguration of primary and secondary metabolism and lowered expression of transcripts in photosynthesis in all three lines. Differences in the number of genes, magnitude and profile of their expression response were also established amongst the lines with a high number belonging to regulatory pathways. In addition, we documented a large number of genes showing constitutive differences in leaf transcript expression between the genotypes at control non-stress conditions. Principal Coordinates Analysis uncovered a high level of structure in the transcriptome response to water stress in each wheat line suggesting genome-wide co-ordination of transcription. Utilising a systems-based approach of analysing the integrated wheat's response to water stress, in terms of biological robustness theory, the findings suggest that each durum line transcriptome responded to water stress in a genome-specific manner which contributes to an overall different strategy of resistance to water stress

La qualité du blé dur dans la région méditerranéenne

National audienc

Stability of carbon isotope discrimination and grain yield in durum wheat

International audienc