Movement patterns of an avian generalist predator indicate functional heterogeneity in agricultural landscape

Landscape Ecology - Biodiversity is closely related to landscape heterogeneity, but both are difficult to evaluate directly. Apex predators, such as raptors, are potential surrogate indicators of...     

Cherry picking by pseudomonads: After a century of research on canker,genomics provides insights into the evolution of pathogenicity towards stone fruits

Bacterial canker disease is a major limiting factor in the growing of cherry and other Prunus species worldwide. At least five distinct clades within the bacterial species complex Pseudomonas syringae are known to be causal agents of the disease. The different pathogens commonly coexist in the field. Reducing canker is a challenging prospect as the efficacy of chemical controls and host resistance may vary against each of the diverse clades involved. Genomic analysis has revealed that the pathogens use a variable repertoire of virulence factors to cause the disease. Significantly, strains of P. syringae pv. syringae possess more genes for toxin biosynthesis and fewer encoding type III effector proteins. There is also a shared pool of key effector genes present on mobile elements such as plasmids and prophages that may have roles in virulence. By contrast, there is evidence that absence or truncation of certain effector genes, such as hopAB, is characteristic of cherry pathogens. Here we highlight how recent research, underpinned by the earlier epidemiological studies, is allowing significant progress in our understanding of the canker pathogens. This fundamental knowledge, combined with emerging insights into host genetics, provides the groundwork for development of precise control measures and informed approaches to breed for disease resistance.     

A new standard area diagram set for assessment of severity of soybean rust improves accuracy of estimates and optimizes resource use

Soybean rust (SBR), caused by Phakopsora pachyrhizi, is the most important yield-damaging fungal disease of soybean due to severe reduction in healthy leaf area and acceleration of leaf fall. In experimental research, SBR severity is estimated visually aided/trained by a standard area diagram (SAD) developed and validated during the mid-2000s (Old SAD). In this study, we propose a new SAD set for SBR with six true-colour diagrams following linear increments (c. 15% increments) amended with four additional diagrams at low (<10%) severities, totalling 10 diagrams (0.2%, 1%, 3%, 5%, 10%, 25%, 40%, 55%, 70%, and 84%). For evaluation, 37 raters were split into two groups. Each assessed severity in a 50-image sample (0.25%–84%), first unaided and then using either the Old SAD or the New SAD. Accuracy, precision, and reliability of estimates improved significantly relative to unaided estimates only when aided by the New SAD (accuracy >0.95). Low precision (<0.78) and a trend of underestimation with an increase in severity were the main issues with the Old SAD, which did not differ from unaided estimates. Simulation to evaluate the impact of the errors by different methods on hypothesis tests, showed that the new SAD was more powerful for detecting the smallest difference in mean control (e.g., 70% vs. 65% disease reduction) than the Old SAD; the latter required a 2-fold increase in sample size to achieve the same power. There is a need to improve some SADs, taking advantage of new knowledge and technology to increase accuracy of the estimates, and to optimize both resource use efficiency and management decisions.     

Crude garlic extract significantly inhibits replication of grapevine viruses

Efforts to control viral diseases of grapevine include the production of certified material and development of virus-resistant transgenic grapevines. However, effective antiviral agents, once the viruses have infected the plants, are still lacking. This study shows that a crude garlic extract has significant antiviral activity against grapevine viruses. Replication of grapevine leafroll-associated virus 2 (GLRaV-2) was obviously inhibited in grapevine cv. Cabernet Sauvignon calli treated with diluted (1:100) garlic extract. The relative RNA levels of GLRaV-2 and grapevine fleck virus (GFkV) in cv. Summer Black grapevine in in vitro-grown plantlets 10 days after treatment with diluted (1:100) garlic extract were about 22% and 20%, respectively, of that in controls. The viral RNA accumulation of GLRaV-2, GFkV, grapevine virus A (GVA), grapevine fanleaf virus (GFLV) and grapevine rupestris stem pitting-associated virus (GRSPaV) in field-grown grapevine cv. Centennial Seedless plants sprayed with diluted (1:100) garlic extract were about 31–40%, 26–38%, 18–31%, 17–42% and 15–18%, respectively, of that in controls. Moreover, the garlic extract treatment led to a significant decrease in viral RNA accumulation of GLRaV-3, GLRaV-2, GVA, GFkV, GFLV, GRSPaV and grapevine Pinot Gris virus in pot-grown grapevine cv. Shine Muscat plants, and viral disease symptoms in these plants were obviously attenuated. In addition, this extract significantly induced expression of pathogenesis-related protein genes and stimulated activity of antioxidant enzymes in grapevines. Taken together, these results indicate that the crude garlic extract acts as a significant inhibitor against a broad range of grapevine viruses.     

Milk vetch dwarf virus infection in the Solanaceae and Caricaceae families in Southeast Asia

Milk vetch dwarf virus (MDV) is an important member of the genus Nanovirus and is transmitted by the aphid Aphis craccivora. MDV has multiple single-stranded DNA genome components, each approximately 1 kb, and two or three alpha-satellite molecules. It mainly infects plants of the legume family Fabaceae. Recently, papaya (Carica papaya) collected in Yesan, South Korea, displaying symptoms of leaf yellowing and dwarfism, was identified as a new host for MDV. To examine the geographical distribution of MDV, papaya samples with symptoms were harvested in South Korea, Vietnam, and Taiwan in August 2018, along with tomato and pepper samples grown in adjacent fields in Vietnam. The results revealed the presence of MDV not only in papaya but also in pepper and tomato. This MDV infection in members of the Solanaceae family was confirmed by Southern blot hybridization performed using a PCR product of segment S as a probe. Based on sequence analysis of three MDV components (M, S, and C3), we verified the presence of three different isolates of MDV in these three countries and homology between sequences of isolates from papaya and from members of the Solanaceae from Vietnam. Taken together, our results clearly demonstrate MDV infection in Vietnam and Taiwan for the first time and confirm that MDV can infect economically important pepper and tomato.     

Temporal disease dynamics and relative importance of sexual and asexual reproduction of grape downy mildew (Plasmopara viticola) in an isolated vineyard in the North Georgia Mountains,USA

The North Georgia Mountains are the southernmost region along the United States East Coast where European wine grapes (Vitis vinifera) are grown commercially. Epidemics of downy mildew, caused by Plasmopara viticola, are frequent and severe, but little is known about the epidemiology and population biology of the pathogen in this region. Disease monitoring in an experimental vineyard from 2015 to 2017 indicated that times of disease onset and progress rates were highly variable across years and cultivars. Oospores were observed microscopically, and simulation with a process-based model indicated presence of conditions favourable for oospore germination in the spring and early summer each year. A total of 409 P. viticola isolates collected over three  years were genotyped with seven microsatellite markers, revealing very high genotypic diversity, which when combined with the observation of oospores is indicative of a sexually reproducing population. Among the 409 isolates, 225 multilocus genotypes (MLGs) were identified, of which 164 were detected only once and 61 were repeated (clonal). Eight MLGs (represented by 28 isolates) were detected across years, suggesting the possibility of asexual overwintering of P. viticola in this region. Across sampling dates, the percentage of isolates belonging to nonrepeated (unique) MLGs ranged from 27.3% to 63.2%. Even towards the end of the annual epidemic, the percentage of isolates in nonrepeated MLGs was still relatively high, around 30%. These MLGs may have originated from oospores germinating late during the growing season, although incomplete sampling at earlier dates and contribution by immigration cannot be fully excluded.     

The effectiveness of consistent roguing in managing banana bunchy top disease in smallholder production in Africa

The removal of infected individuals is a common practice in the management of plant disease outbreaks. It minimizes the contact between healthy individuals and inoculum sources by reducing the infectious window of contaminated individuals. This requires early detection and consistent removal at landscape scale. Roguing of mats with symptoms of banana bunchy top disease (BBTD) in Cavendish banana production systems has been tested in Australia, using trained personnel, but has never been tested in smallholder systems. We studied the effectiveness of long-term consistent roguing in prolonging the productivity of banana orchards under smallholder farming systems in highland banana and plantain dominated production systems in Africa. We assessed the possibility of low-risk seed sourcing from the managed plots. Roguing reduced BBTD incidence to 2% in managed farmer fields and to 10% in experimental field plots, while a nonmanaged field eventually collapsed in the same period. With roguing, new infections decreased monthly compared to an exponential increase in a nonmanaged field. The emergence of new infections in both managed and nonmanaged farms followed a seasonal cycle. BBTD managed plots were a source of low-risk seed for replacing the rogued mats in the same fields, but perhaps not safe for use in nonendemic areas. We conclude that it is possible for smallholder farmers to recover and maintain banana productivity with rigorous roguing, which would entail early identification of symptoms and early removal of diseased mats. Studies are needed on the intensity of roguing under different disease and production conditions.     

Controls on the preservation of biogenic opal in sediments of the eastern tropical pacific

A map of the preservation pattern of siliceous microfossils was constructed from an examination of 125 piston and gravity cores of Quaternary sediments from throughout the eastern tropical Pacific. Preservation is enhanced where high surface water productivity supplies a high input rate of siliceous tests to the sea floor, except in a large area north of 5 degrees N, east of the East Pacific Rise. Here a high input rate of terrigenous silicates may adversely affect preservation of biogenic opal in the sea-floor sediments.     

Human breast cancer: androgen action mediated by estrogen receptor

Growth of the human breast cancer cell line MCF-7 is enhanced by androgens, but only at pharmacological concentrations. Although physiological concentrations of androgens translocate the androgen receptor into the nucleus, no mitogenic effects are observed. By contrast, pharmacological androgens translocate not only the androgen receptor but also the estrogen receptor, and at these high doses significantly increase both DNA and estrogen-dependent protein synthesis. We therefore propose that androgens stimulate MCF-7 cell growth not through the androgen receptor but rather through the estrogen receptor.     

Hormone-sensitive lipase: sequence, expression, and chromosomal localization to 19 cent-q13.3

Hormone-sensitive lipase, a key enzyme in fatty acid mobilization, overall energy homeostasis, and possibly steroidogenesis, is acutely controlled through reversible phosphorylation by catecholamines and insulin. The 757-amino acid sequence predicted from a cloned rat adipocyte complementary DNA showed no homology with any other known lipase or protein. The activity-controlling phosphorylation site was localized to Ser563 in a markedly hydrophilic domain, and a lipid-binding consensus site was tentatively identified. One or several messenger RNA species (3.3, 3.5, or 3.9 kilobases) were expressed in adipose and steroidogenic tissues and heart and skeletal muscle. The human hormone-sensitive lipase gene mapped to chromosome 19 cent-q13.3.