From Transgenesis to Genome Editing in Crop Improvement: Applications, Marketing, and Legal Issues.

The biotechnological approaches of transgenesis and the more recent eco-friendly new breeding techniques (NBTs), in particular, genome editing, offer useful strategies for genetic improvement of crops, and therefore, recently, they have been receiving increasingly more attention. The number of traits improved through transgenesis and genome editing technologies is growing, ranging from resistance to herbicides and insects to traits capable of coping with human population growth and climate change, such as nutritional quality or resistance to climatic stress and diseases. Research on both technologies has reached an advanced stage of development and, for many biotech crops, phenotypic evaluations in the open field are already underway. In addition, many approvals regarding main crops have been granted. Over time, there has been an increase in the areas cultivated with crops that have been improved through both approaches, but their use in various countries has been limited by legislative restrictions according to the different regulations applied which affect their cultivation, marketing, and use in human and animal nutrition. In the absence of specific legislation, there is an on-going public debate with favorable and unfavorable positions. This review offers an updated and in-depth discussion on these issues.

Genomic Approaches to Identify Molecular Bases of Crop Resistance to Diseases and to Develop Future Breeding Strategies.

Plant diseases are responsible for substantial crop losses each year and affect food security and agricultural sustainability. The improvement of crop resistance to pathogens through breeding represents an environmentally sound method for managing disease and minimizing these losses. The challenge is to breed varieties with a stable and broad-spectrum resistance. Different approaches, from markers to recent genomic and 'post-genomic era' technologies, will be reviewed in order to contribute to a better understanding of the complexity of host-pathogen interactions and genes, including those with small phenotypic effects and mechanisms that underlie resistance. An efficient combination of these approaches is herein proposed as the basis to develop a successful breeding strategy to obtain resistant crop varieties that yield higher in increasing disease scenarios.

Proteomic study of a tolerant genotype of durum wheat under salt-stress conditions.

Salinity is one of the major abiotic stress conditions limiting crop growth and productivity. Duilio is a wheat genotype that shows tolerant behavior in both salt-stress and drought-stress conditions. Toward better understanding of the biochemical response to salinity in this genotype of durum wheat, a comparative label-free shotgun proteomic analysis based on normalized spectral abundance factors was conducted on wheat leaf samples subjected to increasing salt-stress levels (100 and 200 mmol L(-1) NaCl) with respect to untreated samples. We found significant changes in 71 proteins for the first stress level, in 83 proteins at the higher salinity level, and in 88 proteins when comparing salt-stress levels with each other. The major changes concerned the proteins involved in primary metabolism and production of energy, followed by those involved in protein metabolism and cellular defense mechanisms. Some indications of different specific physiological and defense mechanisms implicated in increasing tolerance were obtained. The enhanced salinity tolerance in Duilio appeared to be governed by a higher capacity for osmotic homeostasis, a more efficient defense, and an improvement of protection from mechanical stress by increased cell wall lignifications, allowing a better potential for growth recovery.

Stay-green trait-antioxidant status interrelationship in durum wheat (Triticum durum) flag leaf during post-flowering.

Three independent durum wheat mutant lines that show delayed leaf senescence or stay-green (SG) phenotype, SG196, SG310 and SG504, were compared to the parental genotype, cv. Trinakria, with respect to the photosynthetic parameters and the cellular redox state of the flag leaf in the period from flowering to senescence. The SG mutants maintained their chlorophyll content and net photosynthetic rate for longer than Trinakria, thus revealing a functional SG phenotype. They also showed a better redox state as demonstrated by: (1) a lower rate of superoxide anion production due to generally higher activity of the antioxidant enzymes superoxide dismutase and catalase in all of the SG mutants and also of the total peroxidase in SG196; (2) a higher thiol content that can be ascribed to a higher activity of the NADPH-providing enzyme glucose-6-phosphate dehydrogenase in all of the SG mutants and also of the NADP(+)-dependent malic enzyme in SG196; (3) a lower pro-oxidant activity of lipoxygenase that characterises SG196 and SG504 mutants close to leaf senescence. Overall, these results show a general relationship in durum wheat between the SG phenotype and a better redox state. This relationship differs across the different SG mutants, probably as a consequence of the different set of altered genes underlying the SG trait in these independent mutant lines.

Nutritional Components of Wheat Based Food: Composition, Properties, and Uses.

Wheats (bread and durum wheats) and their main end-use products (particularly bread and pasta) have an important role in the Mediterranean diet as they substantially contribute to nutrient intake [...].

Antioxidants and Phenolic Acid Composition of Wholemeal and Refined-Flour, and Related Biscuits in Old and Modern Cultivars Belonging to Three Cereal Species.

Cereals are a good source of phenolics and carotenoids with beneficial effects on human health. In this study, a 2-year evaluation was undertaken on grain, wholemeal and refined-flour of two cultivars, one old and one modern, belonging to three cereal species. Wholemeal of selected cultivars for each species was used for biscuit making. In the grain, some yield-related traits and proteins (PC) were evaluated. In the flours and biscuits, total polyphenols (TPC), flavonoids (TFC), proanthocyanidins (TPAC), carotenoids (TYPC) and antioxidant activities (DPPH and TEAC) were spectrophotometrically determined, whereas HPLC was used for the composition of soluble free and conjugated, and insoluble bound phenolic acids. Species (S), genotype (G) and 'SxG' were highly significant for yield-related and all antioxidant traits, whereas cropping year (Y) significantly affected yield-related traits, PC, TPC, TPAC, TEAC and 'SxGxY' interaction was significant for yield-related traits, TPAC, TYPC, TEAC, DPPH and all phenolic acid fractions. Apart from the TYPC that prevailed in durum wheat together with yield-related traits, barley was found to have significantly higher values for all the other parameters. Generally, the modern cultivars are richest in antioxidant compounds. The free and conjugated fractions were more representative in emmer, while the bound fraction was prevalent in barley and durum wheat. Insoluble bound phenolic acids represented 86.0% of the total, and ferulic acid was the most abundant in all species. A consistent loss of antioxidants was observed in all refined flours. The experimental biscuits were highest in phytochemicals than commercial control. Although barley biscuits were nutritionally superior, their lower consumer acceptance could limit their diffusion. New insights are required to find optimal formulations for better nutritional, sensorial and health biscuits.

Specialized metabolites: Physiological and biochemical role in stress resistance, strategies to improve their accumulation, and new applications in crop breeding and management.

Specialized plant metabolites (SPMs), traditionally referred to as 'secondary metabolites', are chemical compounds involved in a broad range of biological functions, including plant responses to abiotic and biotic stresses. Moreover, some of them have a role in end-product quality with potential health benefits in humans. For this reason, they became an important target of studies focusing on their mechanisms of action and use in crop breeding and management. In this review we summarize the specific role of SPMs in physiological processes and in plant resistance to abiotic and biotic stresses, and the different strategies to enhance their production/accumulation in plant tissues under stress, including genetic approaches (marker-assisted selection and biotechnological tools) and agronomic management (fertilizer applications, cultivation method and beneficial microorganisms). New crop management strategies based on the direct application of the most promising compounds in form of plant residuals or liquid formulations are also described.

Analysis of metabolic and mineral changes in response to salt stress in durum wheat (Triticum turgidum ssp. durum) genotypes, which differ in salinity tolerance.

The key mechanisms of salinity tolerance (ST) in durum wheat were investigated, with five genotypes used to determine changes in morpho-physiological traits and mineral and metabolite contents after exposure to 50, 100 and 200 mM NaCl. Plant growth impairment was evident at the highest salt level. Under this condition, a wide range of shoot Na+ contents and ST were observed within genotypes. However, no significant correlation was seen between ST and Na+ exclusion from the shoots, which indicates that tissue tolerance also has a role. Consistent with this, there was significant correlation between ST and the Na+:K+ ratio in the shoots. Indeed, the maintenance of the shoot Na+ and K+ homeostasis was found to be essential to achieve osmotic adjustment, which relied substantially on inorganic osmolytes, and to avoid toxicity symptoms, such as chlorophyll loss, which appeared only at the highest salinity level. Consistently, the metabolite changes occurred mainly in the shoots, with a dual response to salinity: (i) a conserved response that was common to all the genotypes and resulted in the accumulation of proline and in the depletion of organic acids, including some intermediates of the Krebs cycle; and (ii) a genotype-specific response that involved the accumulation of GABA, threonine, leucine, glutamic acid, glycine, mannose and fructose and appeared related to the different tolerance of genotypes to salinity. The lower magnitude of response to salinity detected in the roots confirmed the major role of the shoots in the determination of ST of durum wheat.

Use of purple durum wheat to produce naturally functional fresh and dry pasta.

In this study, the effects of different milling procedures (roller-milling vs. stone-milling) and pasta processing (fresh vs. dried spaghetti), and cooking on the antioxidant components and sensory properties of purple durum wheat were investigated. Milling and pasta processing were performed using one purple and one conventional non-pigmented durum wheat genotypes, and the end-products were compared with commercial pasta. The results show that the stone milling process preserved more compounds with high health value (total fibre and carotenoids, and in the purple genotype, also anthocyanins) compared to roller-milling. The drying process significantly (p<0.05) reduced the content of anthocyanins (21.42 µg/g vs. 46.32 µg/g) and carotenoids (3.77 µg/g vs. 4.04 µg/g) with respect to the pasteurisation process involved in fresh pasta production. The sensory properties of pasta from the purple genotype did not significantly differ from commercial wholemeal pasta, and its in vitro glycemic index was even lower. Thus, it is possible to consider this genetic material as a good ingredient for the production of functional foods from cereals naturally rich in bioactive compounds.

Novel durum wheat genes up-regulated in response to a combination of heat and drought stress.

We report the effect of heat, drought and combined stress on the expression of a group of genes that are up-regulated under these conditions in durum wheat (Triticum turgidum subsp. durum) plants. Modulation of gene expression was studied by cDNA-AFLP performed on RNAs extracted from flag leaves. By this approach, we identified several novel durum wheat genes whose expression is modulated under different stress conditions. We focused on a group of hitherto undescribed up-regulated genes in durum wheat, among these, 7 are up-regulated by heat, 8 by drought stress, 15 by combined heat and drought stress, 4 are up-regulated by both heat and combined stress, and 3 by both drought and combined stress. The functional characterization of these genes will provide new data that could help the developing of strategies aimed at improving durum wheat tolerance to field stress.