Effects of irrigation regimes on the yield and water use of strawberry

Summary Strawberry plants (Fragaria x annanasa D. cv Chandler) were grown in field plots and in drainage lysimeters under controlled soil moisture regimes. Four irrigation treatments were established by watering the plants when soil water potential reached -0.01, -0.03,-0.05 and -0.07 MPa. The maximum yield was attained at -0.01 MPa soil water potential. Differences in yield were caused by both changes in the number of fruits per plant and in the fresh weight per fruit. Yield reductions were associated with reductions in total assimilation rate resulting from the decreased assimilatory surface area in plants irrigated at lower soil water potentials. The crop water production function calculated on a fruit fresh weight basis resulted in a yield response factor (K _y) of 1.01.     

Purification and Characterization of a Novel Alginate Lyase from a Marine Streptomyces Species Isolated from Seaweed

Alginate, a natural polysaccharide derived from brown seaweed, is finding multiple applications in biomedicine via its transformation through chemical, physical, and, increasingly, enzymatic processes. In this study a novel alginate lyase, AlyDS44, was purified and characterized from a marine actinobacterium, Streptomyces luridiscabiei, which was isolated from decomposing seaweed. The purified enzyme had a specific activity of 108.6 U/mg, with a molecular weight of 28.6 kDa, and was composed of 260 amino acid residues. AlyDS44 is a bifunctional alginate lyase, active on both polyguluronate and polymannuronate, though it preferentially degrades polyguluronate. The optimal pH of this enzyme is 8.5 and the optimal temperature is 45 °C. It is a salt-tolerant alginate lyase with an optimal activity at 0.6 M NaCl. Metal ions Mn²⁺, Co²⁺, and Fe²⁺ increased the alginate degrading activity, but it was inhibited in the presence of Zn²⁺ and Cu²⁺. The highly conserved regions of its amino acid sequences indicated that AlyDS44 belongs to the polysaccharide lyase family 7. The main breakdown products of the enzyme on alginate were disaccharides, trisaccharides, and tetrasaccharides, which demonstrated that this enzyme acted as an endo-type alginate lyase. AlyDS44 is a novel enzyme, with the potential for efficient production of alginate oligosaccharides with low degrees of polymerization.     

Genetic variability following selection for scrapie resistance in six autochthonous sheep breeds in the province of Bolzano (northern Italy)

Scrapie is an ovine transmissible spongiform encephalopathy, and its susceptibility is associated with polymorphisms in the prion protein gene (PRNP). Genetic selection is currently the most effective mean for eradication of the susceptible VRQ allele in favour of resistant ARR allele. Maintenance of genetic diversity should be one of the major objectives in breeding programmes, especially in endangered breeds, and genetic information are an excellent alternative to pedigree data where these information are missing. The aim of our study was to determine changes of genetic variability in six native sheep breeds from autonomous province of Bolzano, northern Italy, following simulation of scrapie selection scenarios. A total of 684 rams were investigated for PRNP polymorphisms and for 10 microsatellite loci to estimate genetic variability. Across all loci, a total of 163 alleles were detected with a mean of 10.4 alleles per locus. Average observed (Ho) and unbiased expected (uHe) heterozygosity overall loci were 0.74 and 0.78, respectively, showing a statistically significant deviation from Hardy–Weinberg equilibrium (HWE) in all breeds. This heterozygosity deficit was confirmed by a positive fixation index (Fis), determining a moderate inbreeding in each breed. Simulating a soft selection, where only rams having at least a VRQ allele should be excluded from reproduction, Ho, uHe and Fis values remained almost unchanged, indicating that genetic variability should not be affected by the removal of these individuals. With a mild selection scenario, considering only rams with at least one ARR allele, we observed a decrease in the mean alleles per breed (8.9) and the maintenance of heterozygosity deficiency, except for two breeds, where it was any longer significant. These results showed that selection strategies allowing use of heterozygous as well homozygous ARR rams might be the right compromise to improve resistance to scrapie and to do not dramatically affect genetic variability of these breeds.     

Assessment of synthetic chemicals for disruption of Rhynchophorus ferrugineus response to attractant-baited traps in an urban environment

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae), is one of the most severe pests of ornamental palm species in urban areas of Mediterranean countries. Aiming to discover inhibitory semiochemicals for RPW population management in urban environments, we conducted electroantennographic (EAG) screenings of 17 commercially available synthetic compounds, representing three groups of plant volatiles (isoprenoids, phenyl propanoid derivatives and fatty acid derivatives) known for their repellent effects toward insects. These tests were followed by trap-based screenings of EAG-active menthone, α-pinene and methyl salicylate, singly and in combination, under urban conditions. In EAG bioassays, RPW antennae of both sexes showed positive dose-dependent responses to 13 of the 17 synthetic chemicals with significant differences among them. In field trapping experiments, conducted in the city of Palermo, Italy, from weeks 31 to 38 in 2010 and 2011, α-pinene, tested singly or in combination with methyl salicylate (2010) or menthone (2011), reduced trap catches by about 30% to 40%. Methyl salicylate and menthone alone were inactive. In conclusion, RPW is significantly affected by α-pinene. This isoprenoid is a promising disruptant for semiochemical-based management of this pest. In addition, identification of a large number of EAG-active chemicals could serve as a database for future design of active repellents or attractants of RPW adults.     

Arbuscular mycorrhizal colonization of vascular plants from the Yungas forests, Argentina

In Argentina, the Yungas forests are among the ecosystems most affected by human activity, with loss of biodiversity. To assess the mycorrhizal status in these ecosystems, the roots of 41 native plant species belonging to 25 families were collected throughout the year from two sites of the Yungas forests. Roots were washed and stained to study the presence of arbuscular mycorrhizas (AM). Morphological types of arbuscular mycorrhizas (Arum and Paris-type) and colonization patterns were identified and photographed. All plants presented AM colonization. The AM colonization patterns varied from single intracellular aseptate hyphae, coils, appresoria, to vesicles and/or arbuscules. Among the species studied, the Paris-type colonization showed to be dominant. Results confirmed that AM hosts are predominant in the Yungas of South American forests.     

Effects Of Thinning In a Water-Limited Holm Oak Forest

ABSTRACT

A natural holm oak forest was selectively thinned to test thinning as a tool to reduce tree mortality, increase productivity, and reverse the recent regression of the dominant species (Quercus ilex) induced by climate change. Thinning increased aboveground productivity and reduced stem mortality in this Mediterranean forest during four years just after thinning, contributing to the maintenance of forest functioning under changing climatic conditions. Q. ilex was the only species positively affected by the thinning: stem growth increased for all stem sizes, and mortality was significantly lower in thinned plots. On the contrary, mortality rates of Phillyrea latifolia and Arbutus unedo were not significantly lower. Stem growth increased for P. latifolia only in the smallest stem-size class. Our results highlight the suitability of selective thinning for improving the forest productivity and ensuring the conservation of Mediterranean coppices. Other benefits of selective thinning, such as a decrease in the risk of fire dispersion and an increase in the water supply for human populations, are also discussed.     

Biflavonoids from Podocalyx loranthoides

Analysis of the ethyl acetate extract of the aerials parts of Podocalyx loranthoides led to the isolation of I 7, II 4'-dimethylamentoflavone (1) and II 4'-methylamentoflavone (2). Compound (1) gave a moderate effect against Leishmania mexicana promastigotes.