Polyphenol oxidase genes as integral part of the evolutionary history of domesticated tetraploid wheat.

Abstract Studying and understanding the genetic basis of polyphenol oxidases (PPO)-related traits plays a crucial role in genetic improvement of crops. A tetraploid wheat collection ( T. turgidum ssp., TWC) was analyzed using the 90K wheat SNP iSelect assay and phenotyped for PPO activity. A total of 21,347 polymorphic SNPs were used to perform genome-wide association analysis (GWA) in TWC and durum wheat sub-groups, detecting 23 and 85 marker-trait associations (MTA). In addition, candidate genes responsible for PPO activity were predicted. Based on the 23 MTAs detected in TWC, two haplotypes associated with low and high PPO activity were identified. Four SNPs were developed and validated providing one reliable marker (IWB75732) for marker assisted selection. The 23 MTAs were used to evaluate the genetic divergence ( FST > 0.25) between the T. turgidum subspecies , providing new information important for understanding the domestication process of Triticum turgidum ssp. and in particular of ssp. carthlicum

Identification and characterization of the sucrose synthase 2 gene (Sus2) in durum wheat

Sucrose transport is the central system for the allocation of carbon resources in vascular plants. Sucrose synthase (SUS), which reversibly catalyzes sucrose synthesis and cleavage, represents a key enzyme in the control of the flow of carbon into starch biosynthesis. In the present study the genomic identification and characterization of the Sus2-2A and Sus2-2B genes coding for SUS in durum wheat (cultivars Ciccio and Svevo) is reported. The genes were analyzed for their expression in different tissues and at different seed maturation stages, in four tetraploid wheat genotypes (Svevo, Ciccio, Primadur, and 5-BIL42). The activity of the encoded proteins was evaluated by specific activity assays on endosperm extracts and their structure established by modeling approaches. The combined results of sucrose synthase 2 expression and activity levels were then considered in the light of their possible involvement in starch yield

Genetic dissection of the relationships between grain yield components by genome-wide association mapping in a collection of tetraploid wheats

Increasing grain yield potential in wheat has been a major target of most breeding programs. Genetic advance has been frequently hindered by negative correlations among yield components that have been often observed in segregant populations and germplasm collections. A tetraploid wheat collection was evaluated in seven environments and genotyped with a 90K SNP assay to identify major and stable quantitative trait loci (QTL) for grain yield per spike (GYS), kernel number per spike (KNS) and thousand-kernel weight (TKW), and to analyse the genetic relationships between the yield components at QTL level. The genome-wide association analysis detected eight, eleven and ten QTL for KNS, TKW and GYS, respectively, significant in at least three environments or two environments and the mean across environments. Most of the QTL for TKW and KNS were found located in different marker intervals, indicating that they are genetically controlled independently by each other. Out of eight KNS QTL, three were associated to significant increases of GYS, while the increased grain number of five additional QTL was completely or partially compensated by decreases in grain weight, thus producing no or reduced effects on GYS. Similarly, four consistent and five suggestive TKW QTL resulted in visible increase of GYS, while seven additional QTL were associated to reduced effects in grain number and no effects on GYS. Our results showed that QTL analysis for detecting TKW or KNS alleles useful for improving grain yield potential should consider the pleiotropic effects of the QTL or the association to other QTLs

Quality characteristics of parental lines of wheat mapping populations

The aim of this work was to evaluate the main quality traits in the parental lines of wheat segregating populations to identify the best for subsequent genetic mapping of the traits. Significant differences (p < 0.001) among wheat genotypes were observed. Many of the examined crosses appeared to be suitable for the purpose, showing differences among parental lines as high as 4.6% for protein content, 6.4% for gluten content, 69 for gluten index, 50 mL for sodium dodecyl sulphate sedimentation volume, and 33.9 g for thousand-kernel weight, whereas differences accounting for 4.8, 2.4, and 7.3 were observed for yellow index, red index and brown index, respectively. The results pointed out that for studying at the same time the quantitative and qualitative features of gluten, the wheat populations derived from Latino x MG29896 and Saragolla x 02-5B-318 could be particularly appropriate. In addition, the latter cross was suitable to deepen the knowledge of yellow index regulation

The Potential of Apulian Olive Biodiversity: The Case of Oliva Rossa Virgin Olive Oil

In this study, the drupes and virgin olive oils extracted from the Oliva Rossa landrace are characterized. Oliva Rossa is an old landrace part of the autochthonous Apulian olive germplasm for which only few data have been reported till now. During the study, the maturity patterns of the drupes had been followed. Four samplings per year were planned, one every 14 days starting from the middle of October. The pigmentation index, the oil content and the total phenolic content of the drupes were measured. Simultaneously, virgin olive oils were extracted at the lab scale and analyzed for the fatty acid composition, the basic quality parameters and the content of minor compounds. The pigmentation pattern of the drupes was different among the years and, despite this trend, at the third sampling time the stage of maximum oil accumulation was always over. The extracted virgin olive oils had a medium to high level of oleic acid. With colder temperatures, a higher level of monounsaturated fatty acids, oleic/linoleic ratio and antioxidants was observed. The phenolic profile was dominated by 3,4-DPHEA-EDA and p-HPEA-EDA while the volatile profile by (E)-2-hexenal and 3-ethyl-1,5-octadiene

Effect of cultivar and roller milling process on the level of phenolic compounds in Italian durum wheat

Phenolic compounds have many favourable effects on human health, arising from their antioxidant activity and capacity to protect critical macromolecules (such as chromosomal DNA, structural proteins and enzymes, low-density lipoproteins, and membrane lipids) from damages induced by active species of oxygen (Dreosti, 2000; Heim et al., 2002). The external layers of wheat caryopses contain interesting levels of various phenolic compounds, and bran extracts have a recognised antioxidant activity and are capable to inhibit lipid peroxidation in human low-density lipoprotein in vitro (Yu et al., 2005). Pasta, both dry and fresh (the latter showing a moisture level of 24-30%), stands out among the wheat-based foods for its typical sensory properties, able to be combined with a wide range of dressings. It is consumed mostly in Italy, but is known and appreciated all over the world. To fulfill nutritional expectations of consumers, whole-wheat pasta is also produced, although in amounts definitely lower than conventional pasta. It shows higher contents of fibre, vitamins and antioxidant substances than conventional pasta, but its consistency can be affected by bran fibre, which interferes with the gluten network (Sivam et al., 2010). The aim of this work has been to assess the feasibility of enrichment of fresh pasta with fluid extracts of phenolic compounds derived from bran. In this way, we intended to produce pasta with increased antioxidant properties, without the technological drawbacks of bran fibre. In particular, the aspects referring to dough characteristics (strength and tenacity to extensibility ratio, determined by Chopin alveograph) and sensory properties of final product have been considered and analysed. Methods involved quantitative descriptive sensory analysis, aroma profiling by Solid Phase Micro Extraction of volatile compounds coupled to Gas Chromatography/Mass Spectroscopy (SPME-GC/MS), and colorimetric determinations. Moreover, various extracting methods and different enrichment levels were evaluated. Every trial was performed in triplicate and submitted to statistical analysis. Regarding the extracting solvents, a preliminary evaluation indicated higher extracting capability of methanol, compared to acetone and ethanol, but only ethanol-derived extracts were selected for the enrichment trials due to their intended edible use. The obtained results indicated that all the extracting methods involving basic hydrolysis lead to higher concentrations of phenolic compounds (with an extracting capability of about 5 mg phenolic compounds, expressed as gallic acid, per g dry bran), as determined by Folin Ciocalteau reaction followed by spectrophotometric measures at 765 nm. However, the subsequent step of neutralization of the same extracting procedure produced NaCl or KCl, which affected the dough characteristics and altered the sensory characteristics of the final products, profiled by considering bulkiness, stickiness, firmness, salty taste, bitter taste, and wholemeal aroma. In particular, a significantly higher value (P < 0.05) of tenacity to extensibility ratio (alveographic P/L) was observed in dough enriched with hydrolised bran extracts, respect to control dough obtained by adding only water. Besides, significantly higher values of firmness, salty taste and wholemeal aroma were observed in pasta enriched with the same hydrolised extracts, while bitter taste did not appear significantly different, at P < 0.05. The colorimetric analysis showed that also colour of enriched pasta was significantly different from that of control, with higher values of both yellow index (b*) and brown index (100 – L). Better results were obtained by avoiding the initial hydrolysis step, which lead to enriched fresh pasta with sensory properties similar to the conventional types, but with enhanced antioxidant activity. In particular, saltiness and consistency were not statistically different from control, while the colorimetric indices appeared higher than in control, with a more intense brownish tone. Also the dough did not show significant differences in the alveographic P/L value (P < 0.05). The aroma profile, determined by SPME-GC/MS analysis of volatile compounds, appeared relatively poor, under the quantitative and qualitative point of view, respect to the usual profile of other cereal-based foods, such as bread. In particular, it was mainly characterized by alcohols (i.e. 1-butanol, 1-pentanol, 1-esanol) and aldehydes (esanal, eptanal, acetaldehyde). In fact, the origin of the volatile compounds observed was essentially imputable to oxidative phenomena related to kneading, in the absence of important biochemical reactions of fermentative or thermal nature due to leavening or baking. In conclusion, this research demonstrated the feasibility of the production of fresh pasta enriched with phenolic compounds derived from bran, assumed that the preliminary preparation of the edible phenolic extract carefully takes into account the best balance between extraction yield and technologic drawbacks