durum wheat

Durum wheat landraces have constituted the main source of Moroccan wheat production until the first half of the last century. This local germplasm is still cultivated in less favorable environments particularly in mountains and sub-Saharan regions. In recent decades of the late 20th and early 21th centuries, the genetic improvement had led to the release of new durum wheat cultivars highly uniform and more productive. The present paper investigates the evolution of genetic variability in terms of productivity and quality related traits using an historical series of Moroccan durum wheat genotypes grouped according to their period of release into "Landraces/ Old cultivars," "Intermediate cultivars," and "Modern cultivars". A significant improvement was achieved in durum wheat Morroccan productivity. Modern cultivars exceed their predecessors in terms of productivity related traits. The genetic gain was clearly associated with a reduction in plant cycle and plant height lowering the straw yield which resulted in an increase of grain yield estimated to 15.42Kg/ha/year. However, results revealed a reduction in terms of almost all quality related traits; -0.12% per year for protein content, -0.30 % per year for gluten strength, -0.31% per year for yellow pigment content, and -0.19% per year for vitreousness. The results underline the important variability in grain quality attributes among landraces genotypes. This local germplasm may be used as sources of quality-improving attributes in durum wheat breeding program to develop new varieties combining both high productivity and grain quality.

Durum wheat (Triticum turgidum subsp. durum) landraces are rapidly disappearing from the main wheat production areas in the Fertile Crescent. Such local landraces are most likely contain geographically specific, ectopically adapted alleles or gene complexes for their harsh environments. A panel of 156 durum wheat landraces and released varieties were assembled from historical collections deposited in national and international gene banks and from a recent active collection mission from selected areas across Jordan. The panel were evaluated under field conditions in two different locations for one growing season. Data for days to heading, plant height, peduncle length, number of spikes spike length, spike weight, grains number, grains weight, number of kernels per spike and thousand-kernel weight were recorded. Results indicate the existence of a wide variation between the tested genotypes for all tested agronomical traits. For heading date, the Jordanian landrace "JDu103" was the earliest under dry environment conditions. Regarding grains weight and spike weight, the Jordanian landrace "JDu105" produced the highest mean value under humid conditions. Another landrace "JDu46" produced the longest spikes and the highest TKW mean value, while the Jordanian landrace "JDu105" produced the heaviest spikes weight mean value, while "JDu100" produced the highest grains number. For molecular analysis, total genomic DNA was extracted from each genotype and then used for SNP genotyping using Illumina iSelect wheat 90k SNP chip. Structure analysis showed that the analyzed durum wheat panel can be divided into three genetically distinct subgroups. The GWAS analysis identified 93 significant markers-traits associations for multiple traits with two QTLs located at 7A and 7B, which seems important for TKW in durum wheat under dry environments. In conclusion, the Jordanian landraces used in this study showed wide genotypic and phenotypic variability, which can be considered by plant breeders for their future use in breeding programs.

Durum wheat (Triticum durum Desf.) is a major cereal crop grown globally. The terminal reduced moisture and heat occurring at the flowering phase are among the main constraints to its production. The molecular basis of tolerance to these threats remains mostly unknown. A subset of 100 genotypes derived from a collection of 384 accessions originating from different countries were investigated for their root growth and architecture under water-limited and well-watered treatments. Two protocols were used, "clear pot" for seminal root angle and "pasta strainer" for mature root angle evaluation. This study reveals that root architecture did not change depending on water treatment. A genotypic variation in root angle was found and two categories of root types were identified: genotypes with (i) superficial and (ii) deep rooting systems. In order to investigate the impact of each root type on yield, all genotypes were tested in the field at multiple locations and under different water regimes. The same set was also tested for heat tolerance in the field under rainfed conditions. Heat was imposed by placing a polytunnel at flowering time to raise the temperature of 10 degrees. The yield, thousand kernel weight and grain number per spike, were evaluated and compared to assess grain fertility, considered as a key trait of heat tolerance. The complete set was genotyped and a genome scan using 8173 SNPs markers developed by 35K Axiom array allowed to identify the genomic regions influencing drought and heat adaptation mechanisms. The pyramiding of this genomic regions could lead to an improved resilience to climate change and increase durum wheat productivity.