Physiological and antioxidant responses of synthetic hexaploid wheat germplasm under drought.

BACKGROUND: As a result of the world population and climate change impact increases (especially in arid environments), there is a critical need for high-yield, drought-tolerant wheat. Synthetic hexaploid wheat derived lines (SHW-DL), were created artificially by crossing different durum wheat cultivars (AABB) with accessions of Aegilops tauschii (DD), a beneficial source of new genes for common bread wheat (Triticum aestivum L). Here, we studied the response of a panel of 91 SHW-DL for drought tolerance based on physiological, antioxidant enzyme activities, and drought tolerance indices. RESULTS: A wide range of variation and high values of heritability observed for grain yield, physiological and antioxidant traits indicating that the SHW-DL panel constitutes a valuable gene source for drought tolerance improvement of wheat. Despite decreases in grain yield (YLD), leaf area index (LAI), and relative water content (RWC) an increase in the content of malondialdehyde (MDA) was observed. Moreover, drought streass increased the antioxidant enzyme activities of ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD), and also photosynthetic pigments, proline (Pro), and MDA content. With higher values of grain yield, physiological and biochemical traits such as photosynthetic pigments, and RWC, and lower content of MDA, and peroxidase (H2O2) activity, SHW-DL performed better compared to common wheat lines under water stress conditions. CONCLUSIONS: Different responses to water stress within the germplasm and between synthetic and common wheat suggest that selection for adaptive and suitable genotypes is possible for drought tolerance in synthetic wheat germplasm. Genotypes 54, 98, 102, 105, 122, 124, 143, 159, 196, and 198 were identified to be directly used in breeding programs or indirectly by crossing them with other wheat germplasm collections.

Drought stress memory in a germplasm of synthetic and common wheat: antioxidant system, physiological and morphological consequences.

Plants have evolved mechanisms of adaptation to fluctuations in their environmental conditions that have been given the term "stress memory". Synthetic wheat offers new hope for breeders to restore useful genes lost during the genetic bottleneck. We aimed to test whether drought priming and seed priming could improve drought tolerance in a diverse germplasm of synthetic and common wheat under field conditions. In this research, 27 wheat genotypes (including 20 synthetics, 4 common local and 3 common exotic bread wheat) were field evaluated under four water environments. These treatments included: 1) normal condition (N), plants were irrigated when 40% of the total available soil water was depleted from the root-zone, 2) seed priming-secondary stress (SD2), only water stress was applied at anthesis when 90% of the total available soil water was depleted and seeds were planted for evaluating, 3) primary stress- secondary stress (D1D2), primary water stress was applied at jointing stage when 70% of the total available soil water was depleted then secondary water stress was applied at the anthesis stage when 90% of the total available soil water was depleted, and 4) secondary stress (D2) only water stress was applied at the anthesis when 90% of the total available soil water was depleted. Our results indicated that improved efficient enzymatic antioxidant system leads to less yield reduction in D1D2 treatment. However, the positive effects of drought priming were more pronounced in drought primed (D1D2) than seed primed treatment (SD2). Synthetic wheat genotypes had a significant superiority in terms of yield, yield components and drought tolerance compared to common wheat genotypes. Nevertheless, the response of genotypes to stress memory was very different. Drought sensitive genotypes had better response to stress memory. Superior genotypes were identified as high yield and drought tolerant genotypes which can be used for future studies.

Potentials of synthetic hexaploid wheats to improve drought tolerance.

Synthetic hexaploid wheat-derived lines (SHW-DL) offers new hope for breeders to restore genes lost during the evolutionary bottleneck. The study of adaptability, variation, and the possibility of selection in SHW-DL for drought tolerance is poorly understood in arid environments. The potential of 184 SHW-DL and their variation for agro-morphological traits were assessed under normal and water stress conditions for 2 years. The mean values of grain yield (YLD) varied from 683.9 g/m2 (water stress) to 992.1 g/m2 (normal conditions). Grain yield decreased by 64 and 71% under water stress in the two growing seasons. High genotypic variation was found for measured traits and drought tolerance. Heritability ranged from 19 (harvest index) to 47% (spike length), whereas grain yield indicated a moderate heritability (32%). Using the assessment of the interrelationship of traits, hectoliter (a quality trait) was correlated with drought tolerance and stability indices. Therefore, it can be considered as an important trait to select drought tolerant genotypes. In the following, the priority of yield components entering the regression model was different in two moisture conditions suggesting different strategies in indirect selection programs to improve yield. Spike m-2 and grain spike-1 indirectly and negatively affected yield through thousand-grain weight (TGW) under normal and water stress conditions, respectively. Furthermore, SHW-DL compared to ordinary wheat were significantly superior in terms of early maturity, dwarfing, yield, TGW, stem diameter, and harvest index. Overall, our findings suggest that SHW-DL are a valuable source for improving wheat yield and drought tolerance, and indirect selection might be possible to improve these complex traits.

Blood compatibility and cell response improvement of poly glycerol sebacate/poly lactic acid scaffold for vascular graft applications.

Plasma surface modification is one of the new methods for improving the surface properties of the scaffold and accelerating tissue regeneration. The aim of this study was to create poly glycerol sebacate/poly lactic acid (PGS/PLA) composite scaffold by electrospun method and modified the scaffold by oxygen plasma for use as a vascular graft. Plasma surface modified PGS/PLA scaffold morphology study showed relatively uniform fibers with an average diameter of 637 ± 149.4 nm and porosity of 82%. The mechanical evaluation of the PGS/PLA scaffold showed properties close to the natural vessels. Atomic force microscopy images exhibited an increase in the roughness of the scaffold after plasma surface modification; however, hemocompatibility studies revealed that it had no adverse effect on blood compatibility. Wettability studies revealed the superhydrophilic property of the modified scaffold (contact angle near to zero). Besides, the human umbilical vein endothelial cells proliferation and adhesion were improved significantly. Obtaining mechanical properties near to the natural vessels due to the suitable composition and significant improvement in blood compatibility and cell growth make the modified PGS/PLA composite a suitable candidate for vascular tissue regeneration.

Molecular diversity assessment of a world collection of safflower genotypes by SRAP and SCoT molecular markers.

Safflower (Carthamus tinctorius L.) is considered as an oil crop that is rich in medicinal and industrial properties. In this study, the genetic diversity of safflower was assessed using 12 polymorphic sequence-related amplified polymorphism (SRAPs) and 11 polymorphic start codon targeted (SCoT) markers in 100 genotypes of safflower gathered from different geographical regions of the world. The 23 primers generated a total of 227 polymorphism fragments with a mean of 68.2% within the range of 3 (SCoT 31 and SCoT 35) to 13 (SCoT 35) bands per primer. Polymorphism per primer ranged between 100% (in Me4-Em1) and 18.1% (in SCoT19), with an average of 36.76%. The polymorphism information contents of the SRAP and SCoT markers were 0.35 and 0.30, respectively, indicating that SRAP markers were more effective than SCoT markers for assessing the degree of genetic diversity of the safflower. The results of the analysis of molecular variance showed a significant difference across cultivated safflower genotypes possessing a high intra-population variation. The examined accessions were categorized into five clusters based on similarity centers: the Middle East containing Iran, Iraq, Turkey, and Tajikistan; the Far East, including India, Pakistan, and Korea; Europe; the American continent; and Africa, including Egypt, Sudan and Libya. The present study shows the effectiveness of employing the mixture of SRAP and SCoT markers in the identification of safflower genetic diversity that would be useful for conservation and population genetics of safflower improvement in further studies.