1,720,984 research outputs found
Recommended from our members
Effects of flooding on survival of Sclerotinia and Verticillium in potato field soils of western Washington
Full text linkSoilborne potato pathogens respond differently to soil flooding. Studies on survival of the sclerotia and microsclerotia of two potato pathogens, Sclerotinia and Verticillium, under greenhouse and field conditions, demonstrated that flooding as a disease management strategy is promising for Sclerotinia but not for Verticillium. Under greenhouse conditions, exposing sclerotia of S. sclerotiorum to constant flooding for three weeks resulted in reduction in germination, ranging from 15 to 88%, although the sclerotia remained intact. At three months, the sclerotia disintegrated but 0 to 18% of the sclerotial fragments retained their viability. No sclerotia were recovered after six months and they completely decomposed. Germination of sclerotia was higher in water only, dried field soil and soil near field capacity treatments, and the sclerotia remained intact after six months. Flooding sclerotia for six weeks at different soil temperatures (4°, 11°, and 20 °C) showed partial disintegration of sclerotia at 11 °C and only 2% germination. At 20 °C, there was complete or near complete decomposition of sclerotia and zero germination. There was apparent reduction of germination at 4 °C although to a lesser extent and at slower rate; germination after six weeks at 4 °C was 30 to 42% while at 18 weeks, there was 0 to 6% germination. In contrast, V. dahliae appeared to be more resistant to flooding when initial inoculum density was >7 CFU/g of soil. V. dahliae was recovered from the soil even after six months flooding. This result was also reflected in field microplot experiment where V. dahliae and total population estimates of Verticillium species were higher in flooded compared to fallowed microplots after 12 months. One year after planting potatoes into microplots either previously flooded or fallowed, progress of early dying symptoms as measured by AUDPC, final percent foliar wilt, recovery of V. dahliae from sampled potato stems, and potato tuber yield were not significantly different between flooded and fallowed microplots. Flooding to eliminate S. sclerotiorum is a potential method of controlling the primary inoculum of white mold in potato fields of western Washington but not for fields with high incidence of Verticillium wilt
Recommended from our members
Effects of temporary flooding rotations on Rhizoctonia solani AG-3 and on soil bacterial communities in western Washington
Full text linkTemporary flooding rotations (TFR) are sometimes employed in the Skagit Valley of western Washington to enhance shorebird habitat and control soilborne potato pathogens, including Rhizoctonia solani. In growth chamber experiments, viability of R. solani AG-3 isolate #13-8 on naturally-infected potato tuber discs diminished by average 23, 40, and 9% over 38 weeks for constant and intermittent flooding, and dry soil treatments, respectively. Viability in inoculated soil-sand mix decreased by average 25% for constant flooding at 10°C, although 100% viability persisted for all treatments at 16°C. Mycoparasitism of R. solani was observed at 10° and 16°C for constant and intermittent flooding, and dry soil treatments only. Survival and pathogenicity of isolate #13-8 in bermed field microplots was assessed with four month Fall/Winter TFR treatments and subsequent potato cropping. Direct baiting indicated that soilborne R. solani increased 44% on average for constant flooding; qPCR primers designed specifically for isolate #13-8 ITS sequence indicated average 17% increase. Fall/Winter TFR had no impact on disease severity; hence it is unlikely that Fall/Winter TFR offers meaningful control of soilborne R. solani in the region. Pre-TFR and post-TFR soil nutrients and properties ie., P, NaHCO-P, K, SO4, Mn, Mg, Ca, Zn, Cu, B, EC, pH, and pH buffer index, responded similarly to Spring/Summer 2013/2014 and Fall/Winter 2013 field flooding events in barrel microplots. For Spring/Summer constant flooding, iron increased 46% average, but nitrate, organic matter, and cation exchange capacity decreased 85, 24, and 27%, respectively. Fall/Winter constant flooding resulted in 33, 4, and 5% increased sodium, organic matter, and cation exchange capacity, respectively. Soil bacterial communities were characterized pre- and post-TFR using Illumina MiSeq . Spring/Summer constant flooding resulted in average increase of Acidobacteria by 14% and Verrucomicrobia by 46%, while Fall/Winter constant flooding resulted in 20% average increase of Bacteroidetes. There was little effect, overall, on bacterial phyla and order composition when post-TFR was compared to pre-TFR communities implying that indigenous soil bacteria have resilient adaptive capabilities. This is the first report of enhanced susceptibility of R. solani to mycoparasitism under saturated soil conditions and the first molecular characterization of bacterial communities in an agricultural soil of western Washington
Recommended from our members
Proactive approaches to managing Potato virus Y in western Washington
Full text linkPotato virus Y (PVY) is one of the oldest known plant viruses, and can cause significant crop and monetary losses. This project investigated: (i) the timing of PVY inoculation and the effects on detection method sensitivity and symptom expression of infected plants; (ii) the potential sources of PVY inoculum in western Washington by investigating five specialty potato cultivars (Austrian Crescent, Banana, Cal White, Purple Majesty, Rosefin Apple) inoculated with PVYO, PVYNTN, and PVYN-Wi, surveying weed species for PVY infection throughout the year, and surveying certified and non-certified seed potatoes for PVY infection purchased from local garden stores; and (iii) the reasons why Washington seed potato growers choose not to adopt the innovation of Hawaii winter grow-out testing with follow-up laboratory testing. PVY symptoms and detection differed by physiological growth stage. Plants inoculated at emergence had the most severe symptoms when compared to other physiological growth stages, while plants inoculated at emergence revealed low to no variability in PVY detection sensitivity between TAS-ELISA and Immunostrips. Cultivar symptoms varied by PVY strain infection. For all cultivars, mosaic was most common on plants infected with PVYO or PVYNTN. Mottle was most common on plants infected with PVYN-Wi. Leaf drop was uncommon, except on Austrian Crescent when infected with PVYO. Veinal necrosis was most common on plants infected with PVYO or PVYNTN. Because of leaf lesions on control plants, this symptom should not be considered viral. Plants infected with PVYN-Wi had the lowest yield of asymptomatic tubers. In Skagit and Whatcom plots, no weedy plant sample tested positive for PVY by TAS-ELISA. However, 54% of organic non-certified seed purchased from local garden stores produced plants positive for PVYO, PVYNTN, and PVYN-Wi. No plants from conventional certified seed were positive for PVY, but 18% of the organic seed tested positive. The primary reasons for nonadoption related to perceptions of the winter grow-out innovation: it is not relatively advantageous, not compatible with current PVY management practices mandated by the WSDA Seed Potato Certification Program, overly complex, not easy to implement on a small-scale, and impacts are difficult to observe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Pea Cyst Nematode
Full text linkBright yellow patches (hot spots) in pea fields signal the presence of these microscopic worms that parasitize roots of pea, Pisum sativum; faba bean, Vicia faba; and vetches Vicia spp. Even green areas of infected fields may harbor low levels of nematodes, cysts, and infected roots. Color photos show damage and disease cycle. Detection methods and prevention by site selection and crop rotation are discussed. 8 pages
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
