Durum wheat (Triticum durum Desf.) Mediterranean landraces as sources of variability for allelic combinations at Glu-1/Glu-3 loci affecting gluten strength and pasta cooking quality

With the aim of identifying durum wheat landraces (LR) with a potential use in breeding programs for gluten strength enhancement, the allelic combinations present at five glutenin loci were determined in a collection of 155 LR from 21 Mediterranean countries. A set of 18 modern cultivars (MC) was used for comparison. Gluten strength was determined by SDS-sedimentation test on grain samples from field experiments conducted during 3 years. A total number of 131 different allelic/banding pattern combinations were found. Taking together high (HMW-) and low (LMW-) molecular weight glutenin subunit loci resulted in 126 combinations in LR, but only nine in MC, which are characterized for having strong gluten. Two LMW-2 type models were identified in the collection and LMW-1 types were absent. LMW-2 was present in 78 % of MC, including the only three with outstanding gluten strength (Ocotillo, Claudio and Meridiano), while 14 % of the LR had LMW-2 and 6 % LMW-2^?. In the LR a known combination LMW-2 (aaa) and three new ones had a positive effect on the gluten strength. LMW-2 models were found in high frequency in LR from Italy and the three Maghreb countries; from medium to low frequencies in genotypes from Turkey, Jordan, Lebanon, Portugal and Spain, and were absent in the remaining countries. The large variability found in LR proved their potential value in breeding to broaden the genetic basis of gluten quality improvement. Genotypes interesting for breeding purposes are identified.     

Effect of patch size on seed removal by harvester ants

The harvester ant Messor barbarus can be responsible for high weed seed losses in dry land cereals in Spain. Because weeds occur in patches, harvester ants have to be able to find and exploit patches. However, seed patches can differ in size and may, therefore, differ in the probability of being discovered and exploited. Here, 90 patches varying in size from 0.25 to 9 m² were created in three 50 × 50 m subareas in a cereal field. Oat seeds were sown as weed seed surrogates in the patches at 2000 seeds m^?2. After 24 h, those remaining were collected and the exploitation rate (the percentage of seeds removed per patch discovered by ants) was estimated. Harvester ant nests and the location of the seed patches were georeferenced and used to estimate distances between them. The patch encounter rate (the proportion of patches discovered by the ants) decreased slightly, but significantly, with decreasing patch size, though not the exploitation rate, which was lowest in the smallest patches (78–94%) and highest in the largest (99–100%). Seed patches that were not found or partially exploited were mostly located in subareas with a lower ant nest density or a longer distance away from the nearest nest than seed patches that were fully exploited. The results of this study indicate that the interaction between the spatial distribution of ant nests and the patchy distribution of seeds can create opportunities for seeds to be subjected to lower levels of predation.     

Effect of water deficit and rewatering on leaf gas exchange and transpiration decline of excised leaves of four grapevine (Vitis vinifera L.) cultivars

Grapevine cultivars are known to differ in their drought adaptation mechanisms, but there is little knowledge on how they behave when recovering after a drought event. The effects of increasing water deficit and recovery after rewatering were evaluated on four widely grown red grapevine cultivars native from different climates (Cabernet Sauvignon, Cs; Garnacha, syn. Grenache, Ga; Merlot, Me; and Tempranillo, Te) through the study of gas exchange (GE) measurements and transpiration decline curves (TDC). As a whole, Ga has proved to be the cultivar best adapted to water deficit, since it showed the highest water use efficiency (WUE) and the greatest water saving ability after leaf excision. Te, on the contrary showed the lowest values for those parameters under increasing stress, although when rewatered showed greater acclimation ability than Cs and Me, remarkably improving its behaviour. The two methodological approaches (GE and TDC) used at different water deficit levels and after rewatering, have complemented each other, allowing a better cultivar characterization than each method would had allowed itself.     

Effect of Sowing Date and Cutting Stage on Yield and Quality of Irrigated Barley and Triticale Used for Forage and Grain

The influence of cutting stage on forage and grain yield and quality has been studied in three barley and one triticale varieties, using two sowing dates in each of two sites. When cut at the first detectable node stage (C.31), forage yield was almost double the yield at the pseudo-stem erect stage (C.30). Barley yielded more forage than triticale at both cutting stages. Both species had similar forage protein content, but forage fibre content was greater in barley than in triticale. Cutting at stage 30 reduced grain yield by about 11 % and at stage 31 by nearly 35 %. Barley and triticale had similar grain yield. Grain protein content was not affected by forage removal, but was significantly greater in triticale than in barley. The later the stage of cutting, the greater was the delay in heading date. Triticale was more responsive to environmental conditions than barley.     

Environmentally induced changes in amino acid composition in the grain of durum wheat grown under different water and temperature regimes in a Mediterranean environment

Amino acid composition is an important feature in determining the nutritional value of wheat grain for human and animal diets. Environmental conditions are known to influence protein quantity as well as grain production and, in turn, amino acid composition. In this study, grain yield, protein content, and amino acid composition were determined in 10 durum wheat genotypes under three water and temperature regimes in a Mediterranean environment. The highest value for grain-protein content (15.7%) was found in the warmer and driest environment and the lowest (12.8%) in the irrigated environment. Although amino acid composition showed significant variation for all genotypes, with the exception of arginine and cysteine, major changes in amino acid composition were caused by environmental conditions and in particular by water availability and temperature during the grain-filling period, which significantly altered the duration of grain development. The amino acids with the highest percentage of variation between environments were tyrosine (26.4%), lysine (23.7%), methionine (20.3%), threonine (19.3%), and valine (15.6%), whereas phenylalanine (5.1%), glycine (6.4%), and aspartic acid (6.8%) showed the least variation between environments. Whereas the content of glutamine, phenylalanine, and proline increased with the decrease in grain-filling duration, the remaining amino acids tended to diminish, presumably because high temperature and drought favored the deposition of gliadins (proteins particularly rich in glutamine and proline), to the detriment of albumins and globulins (proteins especially rich in threonine, lysine, methionine, valine, and histidine). Despite the negative correlations found between the percentage of protein and its content in essential amino acids, the results indicate that reductions in lysine per unit of food were not very pronounced (0.32 to 0.29 g/100 g of flour) with increases of up 22.7% in grain-protein content, whereas threonine did not change and valine even slightly increased.     

Gene specificity is maintained in transient expression assays with protoplasts derived from different tissues of barley

Summary In some cereal species that are still recalcitrant to stable transformation and regeneration, transient expression in isolated protoplasts is a useful tool for the study of gene expression and regulation. We have successfully applied these techniques to barley protoplasts derived from developing endosperm, aleurone, leaves and roots in order to characterize functionally cis-acting motives in two gene promoters, corresponding to trypsin inhibitor BTI-CMe and to sucrose synthase Ss1. Gene specificity is maintained in transient expression assays with protoplasts isolated from these different barley tissues and the pattern of expression parallels the mRNA levels observed for the corresponding genes in the same tissues.Abbreviations CaMV35S 35S-cauliflower mosaic virus promoter - GUS -glucuronidase - MU 4-methyl umbelliferone - NOS nopaline synthase gene - PEG polyethyleneglycol     

Dispersal of durum wheat [<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. ssp. <Emphasis Type="Italic">turgidum</Emphasis> convar. <Emphasis Type="Italic">durum</Emphasis> (Desf.) MacKey] landraces across the Mediterranean basin assessed by AFLPs and microsatellites

A comprehensive characterization of crop germplasm is critical to the optimal improvement of the quality and productivity of crops. Genetic relationships and variability were evaluated among 63 durum wheat landraces from the Mediterranean basin using amplified fragment length polymorphisms (AFLPs) and microsatellites markers. The genetic diversity indices found were comparable to those of other crop species, with average polymorphism information content (PIC) values of 0.24 and 0.70 for AFLP and microsatellites, respectively. The mean number of alleles observed for the microsatellites loci was 9.15. Non-metric multi-dimensional scaling clustered the accessions according to their geographical origin with the landraces from the South shore of the Mediterranean Sea closely related. The results support two dispersal patterns of durum wheat in the Mediterranean basin, one through its north side and a second one through its south side.