Response of Cucurbita spp. to tomato leaf curl New Delhi virus inoculation and identification of a dominant source of resistance in Cucurbita moschata

Tomato leaf curl New Delhi virus is an emerging whitefly-borne species of begomovirus in Mediterranean regions that poses a severe threat to cucurbit crops of the genus Cucurbita. Until now, only two sources of resistance have been identified in Cucurbita spp., these being PI604506 (cv. Large Cheese) and PI381814 (Indian landrace), both of C. moschata. The resistance of cv. Large Cheese is conferred by a single recessive gene located on chromosome 8. The objective of the present investigation was to screen for tomato leaf curl New Delhi virus (ToLCNDV) resistance among 105 accessions drawn from five species of Cucurbita and, if high resistance was found in any of them, determine the mode of inheritance. Screening was conducted using whitefly-mediated inoculation on all 105 accessions. The accessions showing some resistance were further screened by mechanical inoculation as well as by quantitative PCR-based diagnostics. The results showed that, overall, the accessions of C. pepo and C. maxima were the most susceptible, those of C. argyrosperma and C. ecuadorensis intermediate, and those of C. moschata most resistant to ToLCNDV. Only one accession of C. moschata, BSUAL-252, originating from Japan, was highly resistant to ToLCNDV, showing no symptoms after either method of inoculation, and absence of virus accumulation. Upon crossing BSUAL-252 with a susceptible accession of C. moschata, BSUAL-265, the resistance was observed to be conferred by a single dominant gene. This gene is not linked to the genomic region on chromosome 8 where the locus of the previously identified recessive gene for ToLCNDV resistance resides.     

Efficacy of food proteins as carriers for flavonoids

Enrichment of flavonoids in food is often limited by their off-tastes, which might be counteracted by the use of food proteins as carriers of flavonoids. Various milk proteins, egg proteins, and gelatin hydrolysates were compared for their binding characteristics to two flavan-3-ols. Among the proteins tested for their affinities toward epigallocatechin gallate (EGCG), β-casein and gelatin hydrolysates, in particular fish gelatin, were found to be the most promising carriers with an affinity on the order of 10(4) M(-1). A flexible open structure of proteins, as present in random coil proteins, was found to be important. The saturation of binding observed at high flavonoid/protein ratios was used to estimate the maximal binding capacity of each protein. To reach a daily intake of EGCG that has been associated with positive health effects, only 519 mg of gelatin B and 787 mg of β-casein were required to complex EGCG on the basis of their maximal binding capacity. When the absence of turbidity is taken into account, β-casein prevails as carrier. Three selected proteins were further investigated for their binding potential of representative flavonoids differing in their C-ring structure. An increase in hydrophobicity of flavonoids was related to a higher affinity for proteins, and the presence of a gallic acid ester on the C-ring showed an overall higher affinity.     

Milk production performance of Friesian-Holstein cows fed diets containing Medicago sativa, Centrosema pubescens, or groundnut haulms (Arachis hypogaea)

To investigate the effect of feeding dairy cows diets containing lucerne hay, centrosema hay, and groundnut haulms (crop residue) on dry matter intake (DMI), milk yield, and milk composition, nine multiparous Friesian-Holstein cows in their mid-lactation stage were used in a 3?×?3 crossover design replicated three times. Dairy cows fed lucerne hay had significantly (p?<?0.001) higher DMI than dairy cows fed centrosema hay. DMI for cows fed groundnut haulms and lucerne hay was not significantly different. Daily milk yield for dairy cows fed diet containing lucerne hay was significantly (p?<?0.01) higher than that for dairy cows fed diets containing groundnut haulms or centrosema hay. Milk composition and body condition scores of the cows were not significantly affected by either lucerne hay, groundnut haulms, or centrosema hay. Overall, the results in this study indicated that feeding dairy cows diets containing lucerne hay increased milk yield.     

Aggregation of peptides during hydrolysis as a cause of reduced enzymatic extractability of soybean meal proteins

With the purpose of analyzing the size and composition of enzyme-unextractable proteins in differently heat-treated soybean meals, a selection of extractants was screened for their ability to extract these proteins from enzyme-unextractable residues. The largest effects were obtained with urea, urea plus beta-mercaptoethanol, and dilute alkali; the latter extracted up to 87% of the enzyme-unextractable protein. Gel permeation chromatography indicated that a large proportion of the extracted material was of high molecular weight. However, the combined results from gel electrophoresis, LC-MS, and MALDI-ToF MS showed that the extracted protein material was composed of aggregated peptides. The largest aggregates were observed in the enzymatic residues originating from meals heat-treated at high humidity. Extracted aggregates were fully degraded upon subsequent proteolytic treatment.     

Dual role of the pigmentation gene B in affecting carotenoid and vitamin E content in squash (Cucurbita pepo) mesocarp

The yellow and orange colorations of the mesocarp of pumpkins and squash of Cucurbita pepo are due to the presence of carotenoid pigments that also greatly contribute to their nutritional value. Carotenoids, as well as tocopherols (vitamin E), are isoprenoid compounds formed by branches of a common biosynthetic pathway. Photodiode array HPLC analysis was used to simultaneously determine the content and composition of fruit-flesh carotenoids and tocopherols in five pairs of near-isogenic lines differing in the allelic state of genes previously identified as having profound effects on fruit color. The dominant B allele promoted carotenoid accumulation up to 5-fold and prevented tocopherol accumulation in all genetic backgrounds. The dominant L-2 allele doubled carotenoid content and, in combination with the dominant B allele, increased carotenoid content by 10-15-fold as compared to the recessive l-2 allele. The genes D and L-1 had no significant effects on mesocarp tocopherols or carotenoids content. These results indicate that the B gene, which affects both carotenoids and tocopherols, may play a regulatory role in the flux of the isoprenoid pathway products.     

Feeding guilds in Collembola based on digestive enzymes

The digestion ability of 20 species of Collembola sampled from nutrient-poor moist peat meadows was determined. The activity of three carbohydrases was measured, i.e. trehalase, cellulase and chitinase. Species were classified in feeding guilds based on the presence or absence of enzymatic activity. The majority of the samples analysed showed trehalase and cellulase activity, and indicate that Collembola commonly have the ability to digest cell walls of plants and algae, and the contents of fungal hyphae. Most of the species examined had chitinase activity, and are able to digest fungal cell walls. Based on the results, four feeding guilds were distinguished, i.e. herbo-fungivorous grazers (nine species), fungivorous grazers (two species), opportunistic herbofungivores (one species) and omnivore (one species). Five species could not be classified due to low number of samples. One more feeding guild was indicated if the levels of enzymatic activity within species were taken into account, i.e. fungivorous browsers. The results show that most species have the ability to digest the food items reported from gut content analyses. Between species, significant difference in specific enzymatic activity was recorded. These findings suggest that, together with information on feeding guilds, under field conditions the various species in the community differed in their food choice. It is hypothesised that a relationship exists between the mouthpart morphology of Collembola species and specific carbohydrase activity.     

Prediction of molar extinction coefficients of proteins and peptides using UV absorption of the constituent amino acids at 214 nm to enable quantitative reverse phase high-performance liquid chromatography-mass spectrometry analysis

The molar extinction coefficients of 20 amino acids and the peptide bond were measured at 214 nm in the presence of acetonitrile and formic acid to enable quantitative comparison of peptides eluting from reversed-phase high-performance liquid chromatography, once identified with mass spectrometry (RP-HPLC-MS). The peptide bond has a molar extinction coefficient of 923 M(-1) cm(-1). Tryptophan has a molar extinction coefficient that is approximately 30 times higher than that of the peptide bond, whereas the molar extinction coefficients of phenylalanine, tyrosine, and histidine are approximately six times higher than that of the peptide bond. Proline, as an individual amino acid, has a negligible molar extinction coefficient. However, when present in the peptide chain (except at the N terminus), it absorbs approximately three times more than a peptide bond. Methionine has a similar molar extinction coefficient as the peptide bond, while all other amino acids have much lower molar extinction coefficients. The predictability of the molar extinction coefficients of proteins and peptides, calculated by the amino acid composition and the number of peptide bonds present, was validated using several proteins and peptides. Most of the measured and calculated molar extinction coefficients were in good agreement, which shows that it is possible to compare peptides analyzed by RP-HPLC-MS in a quantitative way. This method enables a quantitative analysis of all peptides present in hydrolysates once identified with RP-HPLC-MS.     

Effect of heat treatment on the antioxidant activity, color, and free phenolic acid profile of malt

Green malt was kilned at 95 degrees C following two regimens: a standard regimen (SKR) and a rapid regimen (RKR). Both resulting malts were treated further in a tray dryer heated to 120 degrees C, as was green malt previously dried to 65 degrees C (TDR). Each regimen was monitored by determining the color, antioxidant activity (by both ABTS(.+) and FRAP methods), and polyphenolic profile. SKR and RKR malts exhibited decreased L* and increased b* values above approximately 80 degrees C. TDR malts changed significantly less, and color did not develop until 110 degrees C, implying that different chemical reactions lead to color in those malts. Antioxidant activity increased progressively with each regimen, although with TDR malts this became significant only at 110-120 degrees C. The RKR malt ABTS(.+) values were higher than those of the SKR malt. The main phenolics, that is, ferulic, p-coumaric, and vanillic acids, were monitored throughout heating. Ferulic acid levels increased upon heating to 80 degrees C for SKR and to 70 degrees C for RKR, with subsequent decreases. However, the levels for TDR malts did not increase significantly. The increase in free phenolics early in kilning could be due to enzymatic release of bound phenolics and/or easier extractability due to changes in the matrix. The differences between the kilning regimens used suggest that further modification of the regimens could lead to greater release of bound phenolics with consequent beneficial effects on flavor stability in beer and, more generally, on human health.