Identification of discriminant factors after treatment of resistant and susceptible banana leaves with Fusarium oxysporum f. sp. cubense culture filtrates

Among the most important crops in developing countries are banana and plantain. However, the production is threatened by increasingly virulent forms of Fusarium wilt, and therefore, intensive breeding programmes are being carried out worldwide. As conventional field studies of banana resistance to this disease are time‐consuming and destructive, an easy‐to‐do procedure was previously developed to differentiate field‐grown resistant and susceptible banana cultivars at leaf level. Such a procedure involved the in vitro treatment of fungal culture filtrates on to field‐grown adult leaves and the measurement of lesion areas 48 h later. The present report includes measurements of other indicators such as biochemical compounds. The cultivar ‘Gross Michel’ (susceptible) and cv. ‘FHIA‐01’ (resistant) leaves were treated with Fusarium oxysporum f. sp. cubense race 1 culture filtrates. Evaluations were performed 48 h after leaf treatment. Compared with culture medium‐treated leaves (control treatment), fungal metabolites produced leaf lesions, decreased freephenolic contents and increased protein levels in both cultivars. In ‘FHIA‐01’, the culture filtrate increased contents of cell wall‐linked phenolics and the pool of aldehydes (except malondialdehyde). Fungal metabolites did not cause variations in peroxidase activity, chlorophyll pigment contents or malondialdehyde level in any cultivar. The use of Fisher's linear discriminant analysis to differentiate resistant and susceptible banana cultivars in breeding programmes is also a novel aspect of this report. Such an estimation was performed from a data matrix that included the effects of the fungal metabolites (leaf lesion area and levels of free and cell wall‐linked phenolics, aldehydes, except malondialdehyde, and proteins) on banana leaves of seven cultivars (four susceptible and three resistant).     

Quantitative characterization of flavonoid compounds in Rooibos tea (Aspalathus linearis) by LC-UV/DAD

Rooibos tea originates from the leaves and stems of the indigenous South African plant Aspalathus linearis. It has gained much attention for clinical purposes in the case of nervous tension, allergies (dermatitis), and various indigestive problems. Recently, antioxidative activity was also attributed to the tea on the basis of its flavonoid content. Therefore, an HPLC method using a C(18) reversed phase column was developed for the assay of 10 flavonoids in aqueous and methanolic infusions. Main compounds determined were the dihydrochalcone aspalthin, rutin, and orientin, and their content was in the range of 1.0 to 1.3 mg/g. The identity of detected flavonoids was confirmed by comparing their retention times and UV and MS spectra with those of corresponding standards. In addition, the MS analysis showed evidence of the presence of other compounds such as nothofagin, dihydroisoorientin, and dihydroorientin.     

Uruguayan essential oil. 12. Composition of Nova and Satsuma mandarin oils

The composition of the laboratory-prepared essential oils from Uruguayan Nova and Satsuma mandarins has been studied. The volatile fraction was analyzed by HRGC and HRGC/MS (quadrupole); 79 and 73 components were identified in Nova and Satsuma mandarin oils, respectively. The linear retention indices were calculated for almost all identified components on two different stationary phases. The enantiomeric distribution of beta-pinene, sabinene, limonene, linalool, and alpha-terpineol was studied by multidimensional gaschromatography (MDGC). Polymethoxylated flavones, present in the nonvolatile residue, were analyzed by normal-phase HPLC.     

Direct antioxidant activity of purified glucoerucin, the dietary secondary metabolite contained in rocket (Eruca sativa Mill.) seeds and sprouts

Rocket (Eruca sativa Mill. or Eruca vesicaria L.) is widely distributed all over the world and is usually consumed fresh (leafs or sprouts) for its typical spicy taste. Nevertheless, it is mentioned in traditional pharmacopoeia and ancient literature for several therapeutic properties, and it does contain a number of health promoting agents including carotenoids, vitamin C, fibers, flavonoids, and glucosinolates (GLs). The latter phytochemicals have recently gained attention as being the precursors of isothiocyanates (ITCs), which are released by myrosinase hydrolysis during cutting, chewing, or processing of the vegetable. ITCs are recognized as potent inducers of phase II enzymes (e.g., glutathione transferases, NAD(P)H:quinone reductase, epoxide hydrolase, etc.), which are important in the detoxification of electrophiles and protection against oxidative stress. The major GL found in rocket seeds is glucoerucin, GER (108 +/- 5 micromol g(-)(1) d.w.) that represents 95% of total GLs. The content is largely conserved in sprouts (79% of total GLs), and GER is still present to some extent in adult leaves. Unlike other GLs (e.g., glucoraphanin, the bio-precursor of sulforaphane), GER possesses good direct as well as indirect antioxidant activity. GER (and its metabolite erucin, ERN) effectively decomposes hydrogen peroxide and alkyl hydroperoxides with second-order rate constants of k(2) = 6.9 +/- 0.1 x 10(-)(2) M(-)(1) s(-)(1) and 4.5 +/- 0.2 x 10(-)(3) M(-)(1) s(-) , respectively, in water at 37 degrees C, thereby acting as a peroxide-scavenging preventive antioxidant. Interestingly, upon removal of H(2)O(2) or hydroperoxides, ERN is converted into sulforaphane, the most effective inducer of phase II enzymes among ITCs. On the other hand, ERN (and conceivably GER), like other ITCs, does not possess any chain-breaking antioxidant activity, being unable to protect styrene from its thermally (37 degrees C) initiated autoxidation in the presence of AMVN. The mechanism and relevance of the antioxidant activity of GER and ERN are discussed.     

Optimization of solid-state enzymatic hydrolysis of chestnut using mixtures of alpha-amylase and glucoamylase

Solid-state hydrolysis of starch present in chestnut was assayed in a single step with a mixture of a thermostable alpha-amylase and glucoamylase at three temperatures: 17 and 30 degrees C, for simultaneous hydrolysis and ethanol fermentation, and 70 degrees C, the optimal temperature for these enzymes. Total hydrolysis was only reached at the highest temperature, leading to a more concentrated hydrolysate than in submerged hydrolysis. Mass transfer limitations and starch retrogradation appear as the main causes for the incomplete hydrolysis of chestnut starch in solid-state operation at 17 and 30 degrees C. Even accepting that this limitation causes a 15% reduction of the yield of the hydrolysis with respect to the submerged process or the solid process at high temperature, solid-state hydrolysis at low temperatures seems to be adequate for simultaneous solid-state hydrolysis and fermentation processes.     

Electron microscopy: tight junctions in synapses of the chick ciliary ganglion

Examination of the synaptic membranes in calyciform endings of the chick ciliary ganglion has shown tight junctions selectively located on axon hillocks of postsynaptic neurons. Observations of similar membrane fusion in other junctions that involve electrotonic transmission suggest the possibility of identifying electrotonic junctions by electron microscopy.     

Interactive effects of area and connectivity on the diversity of tachinid parasitoids in highly fragmented landscapes

Although many empirical and theoretical studies have elucidated the effects of habitat fragmentation on the third trophic level, little attention has been paid to the impacts of this driver on more generalist groups of non-hymenopteran parasitoids. Here, we used the highly-diverse group of tachinid flies as an alternative model to test the effects of landscape fragmentation on insect parasitoids. Our aims were: (i) to evaluate the relative importance of habitat area and connectivity losses and their potential interaction on tachinid diversity, (ii) to test whether the effects of habitat fragmentation changes seasonally, and (iii) to further assess the effect of habitat diversity on tachinid diversity and whether different parasitoid-host associations modify the species richness response to fragmentation. In 2012 a pan-trap sampling was conducted in 18 semi-natural grasslands embedded in intensive agricultural landscapes along statistically orthogonal gradients of habitat area, connectivity and habitat diversity. We found an interaction between habitat area and connectivity indicating that tachinid abundance and species richness were more negatively affected by habitat loss in landscapes with low rather than with relatively large habitat connectivity. Although tachinid communities exhibited large within-year species turnover, we found that the effects of landscape fragmentation did not change seasonally. We found that habitat diversity and host association did not affect tachinid species diversity. Our results have important implications for biodiversity conservation as any attempts to mitigate the negative effects of habitat loss need to take the general level of habitat connectivity in the landscape into account.     

Usefulness of molecular-based methods for estimating effective population size in livestock assessed using data from the endangered black-coated Asturcón pony

Empirical evidence of the usefulness of different molecular-based methods to estimate the effective population size (N(e)) for conservation purposes in endangered livestock populations is reported. The black-coated Asturcón pony pedigree (1,981 individuals) was available. Additionally, a total of 267 Asturcón individuals born in 1998, 2002, and 2008 were typed for 15 microsatellites. These yearly cohorts (cohort(1998, 2002, 2008)) included almost all individuals kept for reproduction at the end of the corresponding foaling season. The genealogical realized N(e) was estimated for each cohort by using the individual increase in inbreeding. Molecular N(e) was computed by using 1) linkage disequilibrium [N(e)(()(D)())], 2) a temporal method based on F-statistics [N(e)(()(T)())], 3) an unbiased temporal method [N(e)(()(JR)())], and 4) a Bayesian temporal method [N(e)(()(B)())]. Estimates of increased from cohort(1998) (18.8 ± 5.1) to cohort(2008) (24.9 ± 5.2), illustrating the history of the population and its breeding policy of avoiding matings between close relatives. The estimates of N(e)(()(D)()) were highly biased upward, with the maximum N(e)(()(D)()) value obtained for cohort(2002) (137.0). The estimates of N(e)(()(T)()), N(e)(()(JR)()), and N(e)(()(B)()) showed similar performance. However, N(e)(()(JR)()) estimates were very consistent across cohorts, varying from 14.9 to 15.5 after correcting for the effect of overlapping generations. When the drift signal was not strong (pair cohort(1998)-cohort(2002)), estimates of N(e)(()(T)()) and N(e)(()(B)()) were not realistic. Estimates of N(e)(()(B)()) tended to be biased downward (being 9.0 or below for the sampling pairs including cohort(2008)). Results of N(e)(()(D)()) are more likely to be estimates of the effective number of breeders producing the sample, rather than the effective size for a generation. The temporal methods were strongly affected by a weak drift signal, particularly when samplings were not spaced a sufficient number of generations or a sufficient time apart. The use of molecular-based estimates of N(e) is not straightforward, and their use in livestock conservation programs should be carried out with caution. Sampling strategies (including sampling sizes, sampling periods, and the age structure of the sampled individuals) must be carefully planned to ensure that robust estimates of N(e) are obtained.     

Using digital repeat photography and eddy covariance data to model grassland phenology and photosynthetic CO2 uptake

The continuous and automated monitoring of canopy phenology is of increasing scientific interest for the multiple implications of vegetation dynamics on ecosystem carbon and energy fluxes. For this purpose we evaluated the applicability of digital camera imagery for monitoring and modeling phenology and physiology of a subalpine grassland over the 2009 and 2010 growing seasons.We tested the relationships between color indices (i.e. the algebraic combinations of RGB brightness levels) tracking canopy greenness extracted from repeated digital images against field measurements of green and total biomass, leaf area index (LAI), greenness visual estimation, vegetation indices computed from continuous spectroradiometric measurements and CO₂ fluxes observed with the eddy covariance technique. A strong relationship was found between canopy greenness and (i) structural parameters (i.e., LAI) and (ii) canopy photosynthesis (i.e. Gross Primary Production; GPP). Color indices were also well correlated with vegetation indices typically used for monitoring landscape phenology from satellite, suggesting that digital repeat photography provides high-quality ground data for evaluation of satellite phenology products.We demonstrate that by using canopy greenness we can refine phenological models (Growing Season Index, GSI) by describing canopy development and considering the role of ecological factors (e.g., snow, temperature and photoperiod) controlling grassland phenology. Moreover, we show that canopy greenness combined with radiation use efficiency (RUE) obtained from spectral indices related to photochemistry (i.e., scaled Photochemical Reflectance Index) or meteorology (i.e., MOD17 RUE) can be used to predict daily GPP.Building on previous work that has demonstrated that seasonal variation in the structure and function of plant canopies can be quantified using digital camera imagery, we have highlighted the potential use of these data for the development and parameterization of phenological and RUE models, and thus point toward an extension of the proposed methodologies to the dataset collected within PhenoCam Network.