Changes in hydrophilic and lipophilic antioxidant activity and related bioactive compounds during postharvest storage of yellow and purple plum cultivars

Eight plum cultivars (four dark-purple and four yellow) were harvested at the commercial ripening stage, and changes of fruit quality properties were evaluated during cold storage and subsequent shelf-life, with special emphasis on bioactive compounds (phenolics, anthocyanins and carotenoids) and antioxidant activity (TAA). From the eight plum cultivars, four showed the typical climacteric ripening pattern (‘Blackamber’, ‘Larry Ann’, ‘Golden Globe’ and ‘Songold’) while four behaved as suppressed-climacteric types (‘Golden Japan’ ‘Angeleno’, Black Diamond’ and ‘TC Sun’), the latter being described for the first time. At harvest, large variations in phytochemicals and antioxidant activity were found among cultivars in peel and pulp tissues, although phytochemical concentration and antioxidant activity were higher in the peel than in the flesh (2–40-fold depending on the bioactive compound). During storage, increases in total phenolics for all cultivars (peel and pulp), in total anthocyanin content in the peel of the dark-purple plums, and total carotenoids in the peel and pulp of the yellow cultivars were observed. This behaviour of the bioactive compounds was reflected in TAA changes, since hydrophilic-TAA (H-TAA) was correlated with both phenolics and anthocyanins, while lipophilic-TAA (L-TAA) was correlated with carotenoids. L-TAA comprised about 30–50% of the TAA in plum tissues. Carotenoids and phenolics (and among them the anthocyanins) could be the main lipophilic and hydrophilic compounds contributing to L-TAA and H-TAA, respectively. No significant loss of bioactive compounds and TAA occurred during prolonged plum storage. Moreover, for a better evaluation of the antioxidant potential of plums, the contribution to carotenoids should not be overlooked.     

Enhanced resistance to bacterial infection byErwinia carotovora subsp.atroseptica in transgenic potato plants expressing the attacin or the cecropin SB-37 genes

Blackleg and soft rot diseases, caused by the bacteriumErwinia carotovora, are among the diseases that cause important losses in culture and storage of potato. In this paper, we introduced bacterial resistance into potato, via genes encoding for proteins with antibacterial activity. For this purpose, potato clones were transformed either with the gene encoding the acidic attacin protein fromHyalophora cecropia, or with the gene encoding the cecropin analog peptide SB37. These clones were evaluated for soft rot and blackleg resistance, after inoculation with the bacterial strainErwinia carotovora subsp.atroseptica T7. Results reported in this paper indicate that a considerable percentage of the potato clones (15–22%) showed increased resistance to bacterial infection, revealed by reduced severity of blackleg or soft rot symptoms. Expression of the transgenes was demonstrated in some of the clones by Northern blot analysis. This is the first report indicating that expression of the gene encoding for an attacin protein and for the cecropin SB-37 peptide in transgenic potato confers increased resistance to bacterial infection.     

Is the decline of birds and amphibians in a steppe lake of northern Patagonia a consequence of limnological changes following fish introduction?

• 1. Laguna Blanca, in Laguna Blanca National Park, is a lake in Patagonia which has been designated as a Ramsar site since 1971 because of bird diversity and abundance and importance for nesting, particularly for the black neck swan, Cygnus melanocoryphus. It is also valued for its populations of endemic amphibians, Atelognathus patagonicus and Atelognathus praebasalticus.
• 2. Avian and amphibian populations have decreased dramatically in recent years. Percichthys colhuapiensis, Percichthys trucha (Pisces, Percichthyidae), Salmo trutta and Oncorhynchus mykiss (Pisces, Salmonidae) were introduced into Laguna Blanca in 1965. Since 1986, no Atelognathus frogs have been found. The abundance of swans and coots, which are strongly associated with macrophytes for nesting and feeding, has diminished drastically, whereas piscivorous birds have increased.
• 3. The fishless condition of some neighbouring small lakes with abundant pond weeds, aquatic birds and endemic amphibians, was assessed in order to compare the physical and chemical characteristics and the quantitative composition of the benthos among lakes. Fish presence at Laguna Blanca and its absence at El Burro, Antiñir and Jabón lakes, were confirmed. Compared with previous results, it seems that the abundance of Amphipoda (Hyalella), Copepoda and Cladocera at Laguna Blanca has decreased, while Acari has increased and Notostraca has disappeared. Water transparency has diminished in Laguna Blanca and now is lower than that of fishless lakes.
• 4. P. colhuapiensis were captured only in Laguna Blanca, with the highest captures in the littoral zone. The population shows rapid individual growth in the early years and an absence of fish older than 6 years. The preponderance of benthos and the presence of macrophytes in the gut contents of adult P. colhuapiensis appear to indicate that they are important consumers of these resources.
• 5. This paper concludes that fish introduction in Laguna Blanca led to a complex trophic cascade effect (fish predation on tadpoles, fish competition for avian food, bottom disturbance, zooplankton reduction) producing deleterious effects on the amphibian and bird populations.

Copyright © 2006 John Wiley & Sons, Ltd.     

Mycorrhiza induced resistance in potato plantlets challenged by Phytophthora infestans

Biological control of soil-borne pathogens by arbuscular mycorrhizal (AM) fungi has been repeatedly demonstrated. However, their role in the control of above-ground hemibiotrophic pathogens is less conclusive. Here, we investigated in vitro the impact of an AM fungus on Phytophthora infestans in potato plants. The leaf infection index was decreased in mycorrhizal potato plants. Real-Time Quantitative PCR revealed the induction of two pathogenesis related genes (PR1 and PR2) in the leaves of mycorrhizal plants shortly after infection with P. infestans. These results suggested a systemic resistance in mycorrhizal plants, related to the priming of the two PR genes in potato.     

Vergleichende Untersuchungen an Haaren von Pudu pudu und europäischen Cerviden

The awn and the fur hair of Pudu were investigated. Values of the length are between 14 and 56 mm for the awn hair, and 9 to 36 mm for the fur hair. Hair thickness--especially at the thickest point--ranges from 140 to 236 microns for the awn hair and from 19 to 106 microns for the fur hair. The values of the cuticle scales are between 12 and 18 microns for the length and between 41 and 66 microns for the width. The shape of the scales is rectangular in the basal three quarters (R) and becomes crenated (R/Z) in the apical quarter. The medulla is continuous with large hollow vesicles. The similarity to the hair of european red deer is surprising.     

Chemical control of Delia platura in Phaseolus vulgaris with seed and soil treatments in Chile

A field trial with beans (Phaseolus vulgaris L.) was performed in the Santiago area, to evaluate the insecticidal effect of aldrin, carbofuran, chlorpyriphos, diazinon and lindane, applied to the seed or to the seed furrow, against the bean fly, Delia platura Meigen (Diptera, Anthomyiidae). Plant emergence was reduced with carbofuran and diazinon as a seed treatment, and chlorpyriphos in the furrow, in relation to the checks. All insecticidal treatments reduced the damage to the plants, demonstrating the value of using insecticides for controlling this pest.     

Breeding apomictic bahiagrass (Paspalum notatum Flügge) with improved turf traits

The development of a turf‐type bahiagrass could have a remarkable impact on the billion‐dollar turf industry in the south‐eastern United States. The goals of this study were to (i) select bahiagrass genotypes with improved turf attributes and (ii) determine the reproductive mode and seed fertility of selected genotypes. The population included mutants, wild types, hybrids and standard cultivars evaluated at two locations for two years. Morphological variation was observed and clonal repeatability (H²) ranged from 0.27 to 0.90. Flowering was extremely reduced in some mutants, which also exhibited dark green colour, finer texture and reduced canopy height. Cytoembryological observations revealed that diploids reproduced sexually and tetraploids by obligate or facultative apomixis. Genotypes with superior seed fertility were identified, while others were comparable to the standard cultivars. While mutant plants exhibited great morphological variation, the random mutations did not affect their reproductive mode, validating the use of mutagenesis in apomictic species. The high H² indicated that selection for improved turf attributes could be successfully performed with the advantage of clonal seed propagation.     

Bacterial community structure and detection of putative plant growth-promoting rhizobacteria associated with plants grown in Chilean agro-ecosystems and undisturbed ecosystems

Soil microorganisms with phytase- and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activities are widely studied as plant growth-promoting rhizobacteria (PGPR). Here, we explored the bacterial community structure and occurrence of putative PGPR in plants grown in agro-ecosystems and undisturbed ecosystems from northern, central, and southern Chile. Total rhizobacterial community structure was evaluated by denaturing gradient gel electrophoresis, and dominant bands present in diverse ecosystems were sequenced. Significant differences in total bacterial communities were shown with some bacterial orders (Enterobacteriales, Actinomycetales, and Rhizobiales) being highly similar to both ecosystems. Twenty-nine putative PGPR, showing phytate- and ACC-degrading activities and production of auxin, were selected from across the sites. Based on 16S rRNA gene sequencing, the putative PGPR were characterized as Enterobacteriales (Enterobacter, Serratia, Pantoea, Rahnella, Leclercia), Pseudomonas, and Bacillus, consistent with previously reported PGPR and endophytic bacteria. Beta-propeller phytase genes with similarity to Bacillus were also identified. PGPR from agro-ecosystems appeared to show higher auxin production compared to those from undisturbed ecosystems. This study demonstrates that putative PGPR are widely distributed across Chilean soils. Further understanding of their contribution to the growth and adaptation of plant hosts to local soil conditions may provide opportunity for development of new PGPR in Chilean agriculture.     

Selenobacteria selected from the rhizosphere as a potential tool for Se biofortification of wheat crops

Cereal production in southern Chile is based on ash-derived volcanic Andisols, which present suboptimal levels of available selenium (Se). Strategies are needed to improve Se content in cereal crops and concomitantly improve the nutritional quality of grain. Here, we investigated the occurrence of Se-tolerant bacteria (STB) in Andisols and evaluated Se tolerance and accumulation in STB. The inoculation of wheat with STB and the contributions of these bacteria to Se content in plants were also evaluated under greenhouse conditions. The results showed that Se amendment of Andisols stimulated some bacterial groups (Paenibacillaceae and Brucellaceae) but inhibited others (Clostridia, Burkholderiales, Chitinophagaceae and Oxalobacteraceae), as revealed by denaturing gradient gel electrophoresis. Furthermore, we found four STB isolates that displayed 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase activity) and that carried the acdS gene as revealed by PCR. The selected STB were characterised as Stenotrophomonas, Bacillus, Enterobacter and Pseudomonas according to partial sequencing of the 16S rRNA gene. After 24 h of culture in nutrient broth, the selected STB showed the ability to grow in high Se concentrations (5 and 10 mM) and to accumulate elemental Se in micro- and nanospherical deposits, transforming 50–80 % of the Se initially added. Greenhouse experiments with wheat showed that Se associated with STB (micro- and nanospheres of elemental Se and other intracellular forms) can be translocated into leaves of wheat plantlets.     

Genetic structure of highland papayas (<Emphasis Type="Italic">Vasconcellea pubescens</Emphasis> (Lenné et C. Koch) Badillo) cultivated along a geographic gradient in Chile as revealed by Inter Simple Sequence Repeats (ISSR)

In Chile Vasconcellea pubescens is cropped to produce canned fruit, juice, jam and processed sweets. Additionally this species produces latex with a high level of papain, an important and valuable proteolytic enzyme with industrial applications. In this investigation seven ISSR primers were used to study the level and organization of genetic diversity in 333 samples of V. pubescens. Out of the 114 bands recorded, 63 proved to be polymorphic (P = 55.3%). At the species level, the genetic diversity was rather low (h = 0.01 ± 6,80188E-05, Shannon’s Index I = 0.16 ± 0,000148). The major portion of the genetic diversity was found within groups (65%). The genetic differentiation between the different groups was significant, as the AMOVA analysis suggested (Φ_pt = 0.35). When analysing the Northern area alone, the differentiation increased to Φ_pt = 0.40. When only the Southern area was analysed, Φ_pt decreased to 0.18, indicating greater genetic similarity among the samples. The results generated from Structure and Bayesian Analysis of Population Structure distinguished 8 genetically different groups, five of them located in the north and three in the south. The results are discussed in the light of the growers’ practices.