Translocation of phosphonate from frigoplants to fruits in strawberries

We analysed the phosphonate contents in commercially available strawberry frigoplants and in the fruits grown on these plants. The results show that phosphonates can be translocated from frigoplants to fruits. Thus, strawberry growers may be confronted with phosphonate residues even if they have not applied phosphonates themselves

Testing resistance of apple cultivars to Marssonina coronaria

The apple pathogen Marssonina coronaria (teleomorph: Diplocarpon mali) has recently become a significant problem in Central European organic apple production, causing dark spots on both the leaves and fruit, and early leaf fall. Field observations and resistance testing under controlled conditions indicate that there are differences in resistance to M.coronaria between cultivars. We screened 39 apple cultivars, selected from a large collection of genetic resources, for their susceptibility or resistance to M.coronaria. 1 year old saplings were artificially inoculated under semi-controlled conditions. The development of disease symptoms was observed and assessed several times over more than two months. Symptoms varied largely between cultivars, from small spots on which acervuli immediately developed to large round brown necrotic spots, often with one acervulus in the centre. Leaf fall often started in the middle of the shoot and in parallel on the lower, older leaves. Even though important differences in susceptibility were observed, no cultivar with complete resistance was identified. The observations suggest that resistance to the disease is complex, and involves a number of mechanisms

Identification and quantification of ‘Candidatus Phytoplasma pyri’ in declining trees of a Swiss cider pear orchard after incision treatment at the stem base

Candidatus Orchards of 30 to >100 years old fruit trees used for cider production are endangered by an accumulation of abiotic and biotic stress factors. Among biotic stress factors, diseases such as pear decline (PD) caused by the bacterial pathogen ' Phytoplasma ' contributes to a weakening and reduced life time of affected trees. Since direct treatment of this disease is not possible, approaches have gained attention, which might lead to an increased resilience against this pathogen, such as incisions of the cambium at the graft union at the stem base. Six 35 years old pear trees () of a Swiss cider production orchard, all affected by mild decline were chosen for this study. Four out of them were treated with 2-4 incisions per tree in February 2016. Symptoms were visually assessed during summer and autumn 2016 and 2017, respectively, and ' P ' measured in branch samples with a newly developed duplex TaqMan qPCR assay. No effect could be determined within these two subsequent growing seasons after treatment. Both, visual assessment of symptoms and qPCR measurement of the pathogen in branches did not show any difference between treated and untreated trees. The sequencing of two marker genes of the pathogen detected in this orchard confirmed its identity as ' ' and revealed that it belongs to the major genotype present in Europe

Development of a botanical plant protection product from Larix by-products to protect grapevine from Plasmopara viticola

Extracts from European Larch (Larix decidua) were shown to be efficient to control grapevine downy mildew (Plasmopara viticola) under controlled and field conditions. Larixyl acetate and larixol were identified as the active compounds

An Attribute-Based Approach to Classifying Community-Based Tourism Networks

This conceptual paper proposes the adoption of a collaborative network approach as a prospective means of improving success in implementing community-based tourism (CBT) initiatives. Drawing upon relevant literature, the researchers identify the key attributes that characterise a network-based approach. By proposing alternatives for each attribute, the research provides CBT practitioners with options for making informed decisions about how to build collaboration connecting individual CBT initiatives in multiple locations. The researchers discuss the implications of different approaches for power relations between stakeholders. The proposed framework provides a means of classifying existing CBT networks and analyses the types of network and the circumstances which lead to better outcomes for community development. Further empirical research is required to test the validity of the key network attributes and to develop a comprehensive classification system of CBT networks.School of Hotel and Tourism Managemen

Population density and group size effects on reproductive behavior in a simultaneous hermaphrodite

<p>Abstract</p> <p>Background</p> <p>Despite growing evidence that population dynamic processes can have substantial effects on mating system evolution, little is known about their effect on mating rates in simultaneous hermaphrodites. According to theory, mating rate is expected to increase with mate availability because mating activity is primarily controlled by the male sexual function. A different scenario appears plausible in the hermaphroditic opisthobranch <it>Chelidonura sandrana</it>. Here, field mating rates are close to the female fitness optimum, suggesting that mating activity remains unresponsive to variation in mate availability.</p> <p>Results</p> <p>Applying an experimental design that aims at independent experimental manipulation of density and social group size, we find substantial increases in mate encounter rate with both factors, but no statistically detectable effects on mating rate in <it>C. sandrana</it>. Instead, mating rate remained close to the earlier determined female fitness optimum.</p> <p>Conclusions</p> <p>We demonstrate that mating rate in <it>C. sandrana </it>is largely unresponsive to variation in mate availability and is maintained close to the female fitness optimum. These findings challenge the prevailing notion of male driven mating rates in simultaneous hermaphrodites and call for complementary investigations of mating rate effects on fitness through the male sexual function.</p

Sex-Specific Growth and Reproductive Dynamics of Red Drum in the Northern Gulf of Mexico

The Red Drum Sciaenops ocellatus stock is heavily targeted in the Gulf of Mexico (GOM) by recreational fishers and supports a small commercial fishery in Mississippi. Despite their popularity, little recent work has been done to describe their life history. In this work, we describe sex‐specific growth and reproductive dynamics of Red Drum collected from the northern GOM from September 2016 through October 2017. We evaluated seven candidate growth models and found that the three‐parameter von Bertalanffy growth function (VBGF) was the best candidate length‐at‐age model. No significant difference in growth between sexes was observed with the three‐parameter VBGF, despite the female‐specific curve having a larger mean asymptotic length than the male‐specific curve. All seven candidate growth models predicted similar mean length‐at‐age estimates, and four of them exhibited significant differences in sex‐specific mean length at age, with females reaching a larger length at age than males after age 5. There was no significant difference between the sex‐specific weight‐at‐length relationships. Red Drum are batch spawners that spawn in northern GOM coastal waters during August and September. We estimated 3.7 d between spawns and 10.5 spawning events per female in 2017. Nearly 20% of fish collected during the spawning season were sexually mature but reproductively inactive, indicating the possibility of skipped spawning. The age at 50% maturity was around 3 years (length at 50% maturity = 670 mm TL) in both sexes, but fish were not spawning capable until age 4.5 (703 mm TL) in males and age 5.8 (840 mm TL) in females. Furthermore, elevated gonadosomatic indices were not observed until around age 5–6. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of Red Drum stocks in the northern GOM

A review of the phytochemical support for the shifting defence hypothesis

Several theories have been developed to explain why invasive species are very successful and develop into pest species in their new area. The shifting defence hypothesis (SDH) argues that invasive plant species quickly evolve towards new defence levels in the invaded area because they lack their specialist herbivores but are still under attack by local (new) generalist herbivores. The SDH predicts that plants should increase their cheap, toxic defence compounds and lower their expensive digestibility reducing compounds. As a net result resources are saved that can be allocated to growth and reproduction giving these plants a competitive edge over the local plant species. We conducted a literature study to test whether toxic defence compounds in general are increased in the invaded area and if digestibility reducing compounds are lowered. We specifically studied the levels of pyrrolizidine alkaloids, a toxin which is known for its beneficial and detrimental impact against specialists and generalists, respectively. Digestibility reducers did not show a clear trend which might be due to the small number of studies and traits measured. The meta analysis showed that toxic compounds in general and pyrrolizidine alkaloid levels specifically, increased significantly in the invaded area, supporting the predictions of the SDH that a fast evolution takes place in the allocation towards defence