Reciprocal rewards stabilize cooperation in the mycorrhizal symbiosis

Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.     

Direct determination of paclobutrazol residues in pear samples by liquid chromatography-electrospray tandem mass spectrometry

A rapid and sensitive liquid chromatography/electrospray ionization/tandem mass spectrometry (LC-ESI-MS-MS) method has been developed for the determination of the plant growth regulator paclobutrazol in pear samples. Extraction was performed with methanol by using a high-speed blender Ultra-Turrax, and 10 microL of pear extract was directly injected in the LC-ESI-MS-MS system without any previous sample treatment. The highest sensitivity of the method was achieved under MS-MS conditions obtaining a limit of detection of 0.7 microg/kg and a quantification limit of 5 microg/kg, with a run time of only 5.5 min. Recoveries for paclobutrazol from spiked pear samples at 0.005, 0.05, and 0.5 mg/kg were around 82-102% with relative standard deviations between 2 and 7%. The method was applied to real treated and untreated samples of pears, using quality control samples as a evaluation of the method reliability. Two MS-MS transitions were selected, one for quantification (294 > 70) and the other for confirmation of the analyte (296 > 70). All the experiments were performed in compliance with good laboratory practices.     

Immunoassay to quantify the major peach allergen Pru p 3 in foodstuffs. Differential allergen release and stability under physiological conditions

Pru p 3 is a lipid transfer protein (LTP) that has been identified as the major peach (Prunus persica) allergen. However, little is known about the amount present in both raw and processed foodstuffs. Moreover, the in vivo release upon consumption of peach-containing foods remains unclear. We have developed a sensitive monoclonal antibody-based ELISA for Pru p 3. The method has been applied to measure the allergen levels in foodstuffs and the allergen release under different physiological conditions. A significant variability in all raw peaches and peach-containing foods tested has been detected. The allergen was extracted more efficiently at a low pH, and it was highly resistant to pepsin. This ELISA will be very useful in controlling the allergen concentration in diagnostics, in evaluating threshold levels in provocation tests, and in detecting hidden allergens in processed foods and cosmetics.     

Methodological approach to the study of the formation and physicochemical properties of phosphate-metal-humic complexes in solution

The aim of this work is to study the suitability of the complementary use of ultrafiltration (UF) and the interaction with an anion-exchange resin (AR) to characterize of phosphate-metal-humic complexes in solution. The results indicate that a methodological approach consisting of the validation and calibration of the AR method by the UF method and the further use of the AR method is suitable for characterizing phosphate-metal complexes. Such an approach has proven to be useful for calculating the phosphate maximum binding capacity of iron-humic complexes and stability constants. It might also be used to obtain valuable purified phosphate-metal-humic complexes for further structural characterization.     

Seedling growth of two pioneer tropical tree species in Competition: The role of arbuscular mycorrhizae

The effects of arbuscular mycorrhizae (AM) fungi on growth and survival of two pioneer tropical plant species were studied in a greenhouse experiment for 6 months. One, an early pioneer species (Heliocarpus appendiculatus Turcz., Tiliaceae) and the second, a late pioneer species (Stemmadenia donnell-smithii (Rose) Woodson, Apocynaceae). Three growing conditions were used as competition factors—no competition, with intraspecific and interspecific competitions—along with two different conditions of AM—with and without mycorrhizal inoculum. Mycorrhizal colonization of H. appendiculatus roots was seven-fold more than in S. donnell-smithii. With AM infection, H. appendiculatus did not increase in growth, but showed greater survival in the absence of competition. S. donnell-smithii grew better in the presence of AM fungi and the effect of competition was diminished. S. donnell-smithii with AM fungi infection showed better survival and increase in biomass, making it a better competitor than H. appendiculatus.     

A retrospective sero-epidemiological survey of bovine brucellosis on commercial and communal farming systems in Namibia from 2004 to 2018

Cattle production is the major livestock production activity and the mainstay of Namibia’s economy. Sustained beef exports are contingent on a sound sanitary environment where diseases such as brucellosis are under control. In this retrospective study, 49,718 bovine brucellosis testing results from 2004 to 2018 were analyzed to determine the proportion of sero-positive cattle and herds, and the spatial distribution of positive reactors from commercial and communal areas. In total, 244 positive reactors were identified based on the Rose Bengal Test (RBT) and the Complement Fixation Test (CFT) in series, giving an overall proportion of infected animals of 0.49% (244/49,718; 95% CI, 0.43–0.56%) and an overall proportion of infected herds of 9.26% (78/842; 95% CI, 7.49–11.41%). There was a higher proportion of sero-positive communal herds (33.09%) and cattle (10.27%) than commercial herds (4.67%) and cattle (0.24%; p < 0.05). Annually, the proportion of positive reactors was 0–1.37% in the commercial area and 0–52.38% in the communal areas, with a clear decline in positive reactors in the communal areas. Within the commercial sector, the proportion of positive reactor dairy, beef, and export cattle was 0.19% (51/27,067; 95% CI, 0.14–0.25%), 0.30% (48/16,098; 95% CI, 0.22–0.40%), and 0.33% (16/4811; 95% CI, 0.20–0.54%), respectively. Abortions were found to be the major reason for Brucella testing in the communal areas. About 12.65% (96/759) of abortion-linked sera tested positive in the communal areas, but none were positive in beef or dairy cattle. Widespread vaccination of cattle and robust planned surveillance is recommended to reduce the incidence of the disease, its associated production losses and public health risk.

     

Production performance of sheep and goat breeds at a farm in a semi-arid region of Namibia

Tropical Animal Health and Production - This study retrospectively investigated the effect of breed and season on the lambing/kidding dynamics, growth performance, neonatal viability, and weaning...     

Feeding of yeast(Candida spp.) improves in vitro ruminal fermentation of fibrous substrates

In vitro gas production technique(IVGPT) was used with the objective of determining the inclusion effect of live cells of two strains of Candida yeast on in vitro ruminal fermentation of two fibrous substrates. In order to achieve this, two experiments were performed: A) using oat straw(Avena sativa) as substrate; B) using alfalfa hay(Medicabo sativa) as substrate, comparing the effect of two different strains of Candida genre, both isolated from the rumen, on the mentioned substrates. Levica 25(Candida tropicalis) yeast belongs to the culture collection of the Institute of Animal Science, Cuba, and Levazoot 15(Candida norvegensis) yeast is part of the collection of the Faculty of Zootechnology and Ecology of the Autonomous University of Chihuahua, Mexico. Both strains demonstrated their potential in activating the ruminal fermentation. They stimulated(P<0.0001) the ruminal fermentation of the substrates under study. However, the Levazoot strain stimulated the dry matter(DM) fermentation of alfalfa in 21.43%, more than Levica 25. It is concluded that there is an influence of yeast strain and diet on the rumen environment and, therefore, it is important to select the appropriate strain in every production condition.     

Use of biomass of the marine microalga Isochrysis galbana in the nutrition of goldfish (Carassius auratus) larvae as source of protein and vitamins

The effect of the replacement of fish protein hidrolizate and vitamin premix by freeze‐dried biomass of the marine microalga Isochrysis galbana in the feed for goldfish (Carassius auratus) larvae was tested. Larvae (3.4±0.7 mg) were fed with three experimental microparticulated diets that differ from each other in the percentage of replacement of fish protein hidrolizate (25% or 100%) or vitamin premix by I. galbana biomass. The control diet and the diet containing microalgae biomass as a substitute of 25% of fish protein hidrolizate (MP₂₅) presented the highest survival, being almost 100%, with no significant differences between them. Survival in diets in which 100% of fish protein hidrolizate (MP₁₀₀) or vitamin premix (MV) had been substituted by microalgal biomass was 78% and 66% respectively. Growth, measured as weight, was lower than with the control diet in all treatments in which microalgal biomass was included, with lowest results being obtained with the MP₁₀₀ diet. Differences between treatments and control were lower when growth was measured as length. The harvesting and processing microalgae biomass is crucial to maintain the nutritive value and could be the cause for the obtained results.     

Development of a specific pathogen free population of the Chinese fleshy prawn, Fenneropenaeus chinensis: Part II. Secondary quarantine

The Oceanic Institute (OI), in collaboration with researchers from the University of Arizona (UAZ), established a population of specific pathogen free (SPF) Fenneropenaeus chinensis through Secondary Quarantine (SQ) in Kona, Hawaii. Shrimp were 0.38 g (S.D. ± 0.13 g) when they entered the nursery/growout module of the SQ facility. Juveniles from five maternal families were stocked in separate 230-L nursery tanks, as was a sixth family comprised of shrimp from two of the seven original spawns. After tagging, representative shrimp from all six families were stocked in a 50-m² concrete raceway that was enclosed in a biosecure greenhouse. After 155 days in the growout module, mean shrimp weight was 23.4 g (S.D. ± 7.25 g) and females (29.1 ± 4.61 g) were 74% larger than males (16.7 ± 2.44 g). A Sprung Structure™ was erected to enclose the biosecure maturation and hatchery module of the SQ facility. Broodstock were subjected to an acclimation process where they were kept in seawater at 22 °C, followed by a reduction in water temperature of 1 °C/day until the temperature reached 17 °C. At this time, unilateral eyestalk ablation was performed on female broodstock and water temperature was further reduced at the same rate until it reached 12 °C. After 2 weeks, water temperature was raised to 17 °C at a rate of 1 °C/day to induce ovarian development. Production of an F₁ generation of Fe. chinensis was successfully accomplished using artificial insemination, and representative shrimp from this generation have tested negative for all specifically listed pathogens using histology and PCR/RT-PCR. Of particular interest with Fe. chinensis is their cold tolerance. This species may represent a valuable resource for shrimp farmers in temperate and sub-tropical climates to grow a second “winter” crop, thereby increasing production and profitability for the shrimp farmer.