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Rodrigo Krugner - One of the best experts on this subject based on the ideXlab platform.
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xylella fastidiosa and glassy winged Sharpshooter population dynamics in the southern san joaquin valley of california
Plant Disease, 2020Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Lindsey P. Burbank, David R Haviland, Drake C. StengerAbstract:Xylella fastidiosa is a vector-transmitted bacterial plant pathogen that affects a wide array of perennial crops, including grapevines (Pierce's disease). In the southern San Joaquin Valley of California, epidemics of Pierce's disease of grapevine were associated with the Glassy-Winged Sharpshooter, Homalodisca vitripennis. During the growing season, rates of X. fastidiosa spread in vineyards are affected by changes in pathogen distribution within chronically infected grapevines and by vector population dynamics. Grapevines chronically infected with X. fastidiosa rarely tested positive for the pathogen prior to July, suggesting vector acquisition of X. fastidiosa from grapevines increases as the season progresses. This hypothesis was supported by an increase in number of X. fastidiosa-positive Glassy-Winged Sharpshooters collected from vineyards during July through September. Analysis of insecticide records indicated that vineyards in the study area were typically treated with a systemic neonicotinoid in spring of each year. As a result, abundance of Glassy-Winged Sharpshooters was typically low in late spring and early summer, with abundance of Glassy-Winged Sharpshooter adults increasing in late June and early July of each year. Collectively, the results suggest that late summer is a crucial time for X. fastidiosa secondary spread in vineyards in the southern San Joaquin Valley, because Glassy-Winged Sharpshooter abundance, number of Glassy-Winged Sharpshooters testing positive for X. fastidiosa, and grapevines with detectable pathogen populations were all greatest during this period.
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Targeted Mutations in Xylella fastidiosa Affect Acquisition and Retention by the Glassy-Winged Sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae).
Journal of economic entomology, 2020Co-Authors: Venkatesan G. Sengoda, Rodrigo Krugner, Elaine A. Backus, Xiangyang Shi, Hong LinAbstract:Xylella fastidiosa (Wells) is a xylem-limited bacterium that causes Pierce's disease of grapevines. The bacterium is transmitted by insect vectors such as the Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis (Germar). Experiments were conducted to compare the role of selected X. fastidiosa genes on 1) bacterial acquisition and retention in GWSS foreguts, and 2) transmission to grapevines by GWSS. Bacterial genotypes used were: mutants Xf-ΔpilG, Xf-ΔpilH, Xf-ΔgacA, and Xf-ΔpopP; plus wild type (WT) as control. Results showed that Xf-ΔpilG had enhanced colonization rate and larger numbers in GWSS compared with WT. Yet, Xf-ΔpilG exhibited the same transmission efficiency as WT. The Xf-ΔpilH exhibited poor acquisition and retention. Although initial adhesion, multiplication, and retention of Xf-ΔpilH in GWSS were almost eliminated compared with WT, the mutation did not reduce transmission success in grapevines. Overall, Xf-ΔgacA showed colonization rates and numbers in foreguts similar to WT. The Xf-ΔgacA mutation did not affect initial adhesion, multiplication, and long-term retention compared with WT, and was not significantly diminished in transmission efficiency. In contrast, numbers of Xf-ΔpopP were variable over time, displaying greatest fluctuation from highest to lowest levels. Thus, Xf-ΔpopP had a strong, negative effect on initial adhesion, but adhered and slowly multiplied in the foregut. Again, transmission was not diminished compared to WT. Despite reductions in acquisition and retention by GWSS, transmission efficiency of genotypes to grapevines was not affected. Therefore, in order to stop the spread of X. fastidiosa by GWSS using gene-level targets, complete disruption of bacterial colonization mechanisms is required.
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Mating Disruption by Vibrational Signals: Applications for Management of the Glassy-Winged Sharpshooter
Biotremology: Studying Vibrational Behavior, 2019Co-Authors: Shira D. Gordon, Rodrigo KrugnerAbstract:The Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis, is a generalist insect and a major pest of grapevines. GWSS is a vector of the bacterium Xylella fastidiosa, causal agent of Pierce’s disease that can lead to grapevine death within few years after infection. This chapter discusses the problem and current GWSS control methods. Then, the focus changes to efforts in developing a novel control method that uses synthetic vibrational signals to disrupt mating and, thus, population growth. A step-by-step method for creating effective playback signals is described and discussed. The method was termed “D.I.E.,” which stands for Describe, Identify, and Execute. The first step is to describe the basic biology of the insect pest with emphasis on communication behaviors. From there, one can begin identifying which candidate signals disrupt communication. Finally, execution tests are conducted to determine which signals effectively disrupt mating in laboratory, and more importantly, in the field. While there are still steps needed for large-scale implementation in the field, the basic biological questions related to whether synthetic vibrational signals can disrupt mating are answered affirmatively. The next direction will be to develop a mechanism of signal transmission across large areas. In addition, season long field trials are needed, taking into consideration natural insect movements into and out of treated areas.
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Mating vibrational signal transmission through and between plants of an agricultural pest, the Glassy-Winged Sharpshooter
The Journal of the Acoustical Society of America, 2018Co-Authors: Shira D. Gordon, Benjamin Tiller, James F. C. Windmill, Peter M. Narins, Rodrigo KrugnerAbstract:The agricultural pest, Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis, relies primarily on successful vibrational communication across its home plant. Males and females engage in a vibrational duet to identify correct species, attractiveness of mate, and location on the plant. The signal produced by these animals has a dominant frequency component between 80 and 120 Hz, with harmonics spaced approximately 100 Hz apart. However, our analysis revealed that not all harmonics are present in every recorded signal. Therefore, we sought to understand how the GWSS vibrational communication signal changes over distance on the plant. We have confirmed that first, with increasing distance fewer high frequency harmonics are present. Second, at distances of only 50 cm, there is a difference in the latency of signal arrival based on the frequency, with higher frequencies arriving sooner. Finally, the animal appears to generate no airborne signal component, yet, the low frequencies are clearly detectable in ...
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Effects of Energy Reserves and Diet on Glassy-Winged Sharpshooter Egg Maturation.
Journal of economic entomology, 2017Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Christopher M. Wallis, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter is an invasive insect capable of transmitting the plant pathogen Xylella fastidiosa. As rates of pathogen spread are a function of vector abundance, identification of factors contributing to Glassy-Winged Sharpshooter egg production will aid in predicting population growth. Here, effects of stored energy reserves and adult diet on Glassy-Winged Sharpshooter egg maturation were evaluated. To estimate energy reserves available to adult females at the beginning of feeding assays, residuals from a regression of wet weight on size were used. Analysis of a subset of females sacrificed at the beginning of feeding assays, demonstrated that females with a positive residual wet weight had higher lipid content and carried more eggs than females with a negative residual wet weight. To evaluate effects of diet and energy reserves on egg maturation, energy reserves available to females entering feeding assays on cowpea and grapevine were estimated. For females held on cowpea, residual wet weight and quantity of excreta produced over a 6-d feeding period affected egg production. In contrast, for females held on grapevine, only residual wet weight affected egg production. Comparison of cowpea and grapevine xylem sap determined that eight amino acids were more concentrated in xylem sap from cowpea than from grapevine. Collectively, the results suggest that Glassy-Winged Sharpshooter population growth within crop monocultures will not depend solely on the nutritional quality of the specific crop for producing mature eggs but also on the quantity of energy reserves accumulated by females prior to entering that crop habitat.
Mark S. Sisterson - One of the best experts on this subject based on the ideXlab platform.
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xylella fastidiosa and glassy winged Sharpshooter population dynamics in the southern san joaquin valley of california
Plant Disease, 2020Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Lindsey P. Burbank, David R Haviland, Drake C. StengerAbstract:Xylella fastidiosa is a vector-transmitted bacterial plant pathogen that affects a wide array of perennial crops, including grapevines (Pierce's disease). In the southern San Joaquin Valley of California, epidemics of Pierce's disease of grapevine were associated with the Glassy-Winged Sharpshooter, Homalodisca vitripennis. During the growing season, rates of X. fastidiosa spread in vineyards are affected by changes in pathogen distribution within chronically infected grapevines and by vector population dynamics. Grapevines chronically infected with X. fastidiosa rarely tested positive for the pathogen prior to July, suggesting vector acquisition of X. fastidiosa from grapevines increases as the season progresses. This hypothesis was supported by an increase in number of X. fastidiosa-positive Glassy-Winged Sharpshooters collected from vineyards during July through September. Analysis of insecticide records indicated that vineyards in the study area were typically treated with a systemic neonicotinoid in spring of each year. As a result, abundance of Glassy-Winged Sharpshooters was typically low in late spring and early summer, with abundance of Glassy-Winged Sharpshooter adults increasing in late June and early July of each year. Collectively, the results suggest that late summer is a crucial time for X. fastidiosa secondary spread in vineyards in the southern San Joaquin Valley, because Glassy-Winged Sharpshooter abundance, number of Glassy-Winged Sharpshooters testing positive for X. fastidiosa, and grapevines with detectable pathogen populations were all greatest during this period.
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Infection of Blueberry Cultivar 'Emerald' with a California Pierce's Disease Strain of Xylella fastidiosa and Acquisition by Glassy-Winged Sharpshooter.
Plant disease, 2019Co-Authors: Lindsey P. Burbank, Mark S. Sisterson, Michael L. O’learyAbstract:Bacterial leaf scorch disease caused by Xylella fastidiosa occurs in southern highbush blueberry varieties in the southeastern United States. Susceptibility to X. fastidiosa varies by blueberry cultivar, and these interactions are often strain-specific. Xylella fastidiosa subsp. fastidiosa is the causal agent of Pierce's disease in grapevines, and it has been problematic in the San Joaquin Valley of California since the introduction of the Glassy-Winged Sharpshooter (Homalodisca vitripennis). The Glassy-Winged Sharpshooter is known to feed on blueberry, a crop that is expanding in the San Joaquin Valley. Currently, little is known about the potential for the spread of X. fastidiosa between grape and blueberry in this region. The ability of a Pierce's disease strain of X. fastidiosa from the San Joaquin Valley to cause disease in southern highbush blueberry and the potential for the Glassy-Winged Sharpshooter to transmit X. fastidiosa between blueberry and grapevine were investigated. Experimental inoculations showed that the X. fastidiosa subsp. fastidiosa strain Bakersfield-1 can cause disease in blueberry cv. Emerald, and that the Glassy-Winged Sharpshooter can acquire X. fastidiosa from artificially inoculated blueberry plants under laboratory conditions. Understanding the possibility for X. fastidiosa strains from the San Joaquin Valley to infect multiple crops grown in proximity is important for area-wide pest and disease management.
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Effects of Nymphal Diet and Adult Feeding on Allocation of Resources to Glassy-Winged Sharpshooter Egg Production.
Environmental entomology, 2018Co-Authors: Mark S. Sisterson, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter is an invasive insect capable of transmitting the bacterial pathogen Xylella fastidiosa. Pre-oviposition periods of laboratory-reared Glassy-Winged Sharpshooters are variable. Here, two questions were addressed: does nymphal diet affect pre-oviposition period and how do allocation patterns of resources differ for females that produce eggs versus females that do not? Nymphs were reared on one of three host plant species: cowpea, sunflower, or sorghum. Half of the females were sacrificed at emergence. The remaining adult females were held on cowpea, a host plant species known to support egg maturation via adult feeding. Females were sacrificed on the day of first oviposition or after 9 wk if no eggs were deposited. Females reared as nymphs on sorghum had longer development times and were smaller (head capsule width and hind tibia length) than females reared as nymphs on cowpea and sunflower. However, nymphal diet did not affect percentage of dry weight that was lipid at emergence. Further, nymphal diet did not affect time to deposition of the first egg mass or total number of eggs matured at the time of first oviposition. Egg production reduced the allocation of resources to insect bodies, with body lipid content decreasing with increasing egg production. In general, females increased wet weight 1.4-fold during the first week after adult emergence, with wet weights plateauing over the remaining 9 wk that adults were monitored. Thus, it seems reasonable to hypothesize that resources required for egg production were acquired via adult feeding during the first week after adult emergence.
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Effects of Energy Reserves and Diet on Glassy-Winged Sharpshooter Egg Maturation.
Journal of economic entomology, 2017Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Christopher M. Wallis, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter is an invasive insect capable of transmitting the plant pathogen Xylella fastidiosa. As rates of pathogen spread are a function of vector abundance, identification of factors contributing to Glassy-Winged Sharpshooter egg production will aid in predicting population growth. Here, effects of stored energy reserves and adult diet on Glassy-Winged Sharpshooter egg maturation were evaluated. To estimate energy reserves available to adult females at the beginning of feeding assays, residuals from a regression of wet weight on size were used. Analysis of a subset of females sacrificed at the beginning of feeding assays, demonstrated that females with a positive residual wet weight had higher lipid content and carried more eggs than females with a negative residual wet weight. To evaluate effects of diet and energy reserves on egg maturation, energy reserves available to females entering feeding assays on cowpea and grapevine were estimated. For females held on cowpea, residual wet weight and quantity of excreta produced over a 6-d feeding period affected egg production. In contrast, for females held on grapevine, only residual wet weight affected egg production. Comparison of cowpea and grapevine xylem sap determined that eight amino acids were more concentrated in xylem sap from cowpea than from grapevine. Collectively, the results suggest that Glassy-Winged Sharpshooter population growth within crop monocultures will not depend solely on the nutritional quality of the specific crop for producing mature eggs but also on the quantity of energy reserves accumulated by females prior to entering that crop habitat.
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Effects of Xylem-Sap Composition on Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Egg Maturation on High- and Low-Quality Host Plants.
Environmental entomology, 2017Co-Authors: Mark S. Sisterson, Christopher M. Wallis, Drake C. StengerAbstract:Glassy-Winged Sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the Glassy-Winged Sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in egg production, effects of xylem-sap chemistry on Glassy-Winged Sharpshooter egg maturation was compared for females confined to cowpea and sunflower. Females confined to cowpea consumed more xylem-sap than females held on sunflower. In response, females held on cowpea produced more eggs, had heavier bodies, and greater lipid content than females held on sunflower. Analysis of cowpea and sunflower xylem-sap found that 17 of 19 amino acids were more concentrated in cowpea xylem-sap than in sunflower xylem-sap. Thus, decreased consumption of sunflower xylem-sap was likely owing to perceived lower quality, with decreased egg production owing to a combination of decreased feeding and lower return per unit volume of xylem-sap consumed. Examination of pairwise correlation coefficients among amino acids indicated that concentrations of several amino acids within a plant species were correlated. Principal component analyses identified latent variables describing amino acid composition of xylem-sap. For females held on cowpea, egg maturation was affected by test date, volume of excreta produced, and principal components describing amino acid composition of xylem-sap. Principal component analyses aided in identifying amino acids that were positively or negatively associated with egg production, although determining causality with respect to key nutritional requirements for Glassy-Winged Sharpshooter egg production will require additional testing.
Drake C. Stenger - One of the best experts on this subject based on the ideXlab platform.
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xylella fastidiosa and glassy winged Sharpshooter population dynamics in the southern san joaquin valley of california
Plant Disease, 2020Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Lindsey P. Burbank, David R Haviland, Drake C. StengerAbstract:Xylella fastidiosa is a vector-transmitted bacterial plant pathogen that affects a wide array of perennial crops, including grapevines (Pierce's disease). In the southern San Joaquin Valley of California, epidemics of Pierce's disease of grapevine were associated with the Glassy-Winged Sharpshooter, Homalodisca vitripennis. During the growing season, rates of X. fastidiosa spread in vineyards are affected by changes in pathogen distribution within chronically infected grapevines and by vector population dynamics. Grapevines chronically infected with X. fastidiosa rarely tested positive for the pathogen prior to July, suggesting vector acquisition of X. fastidiosa from grapevines increases as the season progresses. This hypothesis was supported by an increase in number of X. fastidiosa-positive Glassy-Winged Sharpshooters collected from vineyards during July through September. Analysis of insecticide records indicated that vineyards in the study area were typically treated with a systemic neonicotinoid in spring of each year. As a result, abundance of Glassy-Winged Sharpshooters was typically low in late spring and early summer, with abundance of Glassy-Winged Sharpshooter adults increasing in late June and early July of each year. Collectively, the results suggest that late summer is a crucial time for X. fastidiosa secondary spread in vineyards in the southern San Joaquin Valley, because Glassy-Winged Sharpshooter abundance, number of Glassy-Winged Sharpshooters testing positive for X. fastidiosa, and grapevines with detectable pathogen populations were all greatest during this period.
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Effects of Nymphal Diet and Adult Feeding on Allocation of Resources to Glassy-Winged Sharpshooter Egg Production.
Environmental entomology, 2018Co-Authors: Mark S. Sisterson, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter is an invasive insect capable of transmitting the bacterial pathogen Xylella fastidiosa. Pre-oviposition periods of laboratory-reared Glassy-Winged Sharpshooters are variable. Here, two questions were addressed: does nymphal diet affect pre-oviposition period and how do allocation patterns of resources differ for females that produce eggs versus females that do not? Nymphs were reared on one of three host plant species: cowpea, sunflower, or sorghum. Half of the females were sacrificed at emergence. The remaining adult females were held on cowpea, a host plant species known to support egg maturation via adult feeding. Females were sacrificed on the day of first oviposition or after 9 wk if no eggs were deposited. Females reared as nymphs on sorghum had longer development times and were smaller (head capsule width and hind tibia length) than females reared as nymphs on cowpea and sunflower. However, nymphal diet did not affect percentage of dry weight that was lipid at emergence. Further, nymphal diet did not affect time to deposition of the first egg mass or total number of eggs matured at the time of first oviposition. Egg production reduced the allocation of resources to insect bodies, with body lipid content decreasing with increasing egg production. In general, females increased wet weight 1.4-fold during the first week after adult emergence, with wet weights plateauing over the remaining 9 wk that adults were monitored. Thus, it seems reasonable to hypothesize that resources required for egg production were acquired via adult feeding during the first week after adult emergence.
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Effects of Energy Reserves and Diet on Glassy-Winged Sharpshooter Egg Maturation.
Journal of economic entomology, 2017Co-Authors: Mark S. Sisterson, Rodrigo Krugner, Christopher M. Wallis, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter is an invasive insect capable of transmitting the plant pathogen Xylella fastidiosa. As rates of pathogen spread are a function of vector abundance, identification of factors contributing to Glassy-Winged Sharpshooter egg production will aid in predicting population growth. Here, effects of stored energy reserves and adult diet on Glassy-Winged Sharpshooter egg maturation were evaluated. To estimate energy reserves available to adult females at the beginning of feeding assays, residuals from a regression of wet weight on size were used. Analysis of a subset of females sacrificed at the beginning of feeding assays, demonstrated that females with a positive residual wet weight had higher lipid content and carried more eggs than females with a negative residual wet weight. To evaluate effects of diet and energy reserves on egg maturation, energy reserves available to females entering feeding assays on cowpea and grapevine were estimated. For females held on cowpea, residual wet weight and quantity of excreta produced over a 6-d feeding period affected egg production. In contrast, for females held on grapevine, only residual wet weight affected egg production. Comparison of cowpea and grapevine xylem sap determined that eight amino acids were more concentrated in xylem sap from cowpea than from grapevine. Collectively, the results suggest that Glassy-Winged Sharpshooter population growth within crop monocultures will not depend solely on the nutritional quality of the specific crop for producing mature eggs but also on the quantity of energy reserves accumulated by females prior to entering that crop habitat.
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Effects of Xylem-Sap Composition on Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Egg Maturation on High- and Low-Quality Host Plants.
Environmental entomology, 2017Co-Authors: Mark S. Sisterson, Christopher M. Wallis, Drake C. StengerAbstract:Glassy-Winged Sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the Glassy-Winged Sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in egg production, effects of xylem-sap chemistry on Glassy-Winged Sharpshooter egg maturation was compared for females confined to cowpea and sunflower. Females confined to cowpea consumed more xylem-sap than females held on sunflower. In response, females held on cowpea produced more eggs, had heavier bodies, and greater lipid content than females held on sunflower. Analysis of cowpea and sunflower xylem-sap found that 17 of 19 amino acids were more concentrated in cowpea xylem-sap than in sunflower xylem-sap. Thus, decreased consumption of sunflower xylem-sap was likely owing to perceived lower quality, with decreased egg production owing to a combination of decreased feeding and lower return per unit volume of xylem-sap consumed. Examination of pairwise correlation coefficients among amino acids indicated that concentrations of several amino acids within a plant species were correlated. Principal component analyses identified latent variables describing amino acid composition of xylem-sap. For females held on cowpea, egg maturation was affected by test date, volume of excreta produced, and principal components describing amino acid composition of xylem-sap. Principal component analyses aided in identifying amino acids that were positively or negatively associated with egg production, although determining causality with respect to key nutritional requirements for Glassy-Winged Sharpshooter egg production will require additional testing.
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Effects of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Feeding, Size, and Lipid Content on Egg Maturation.
Journal of economic entomology, 2015Co-Authors: Mark S. Sisterson, Christopher M. Wallis, Drake C. StengerAbstract:The Glassy-Winged Sharpshooter (Homalodisca vitripennis) is synovigenic and must feed as an adult to produce eggs. Egg maturation rates depend on the host plant species provided to the adult female for feeding and are variable for females provided with the same host plant species. Here, the contribution of female size and lipid content to variation in egg maturation rates among females held on the same host plant species was assessed. To assess effects of female size and lipid content on egg maturation, feeding assays followed by measurements of egg load, female size, and lipid content were conducted. To accomplish this, females were field collected and held on cowpea until producing approximately 0, 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colorimetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding (12 ml of excreta) but decelerated with additional feeding (>12 ml of excreta). In contrast, low levels of feeding (12 ml of excreta) resulted in little egg production, with rates of egg production accelerating with additional feeding (>12 ml of excreta). Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. In agreement, probability that a female carried eggs increased with body lipid content in the 0-, 12-, and 25-ml feeding treatments. Across treatments, larger females carried more eggs than smaller females. Collectively, results suggest that variation in Glassy-Winged Sharpshooter egg maturation rates partially may be explained by availability of lipid reserves at the start of a feeding bout and female size.
Elaine A. Backus - One of the best experts on this subject based on the ideXlab platform.
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Targeted Mutations in Xylella fastidiosa Affect Acquisition and Retention by the Glassy-Winged Sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae).
Journal of economic entomology, 2020Co-Authors: Venkatesan G. Sengoda, Rodrigo Krugner, Elaine A. Backus, Xiangyang Shi, Hong LinAbstract:Xylella fastidiosa (Wells) is a xylem-limited bacterium that causes Pierce's disease of grapevines. The bacterium is transmitted by insect vectors such as the Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis (Germar). Experiments were conducted to compare the role of selected X. fastidiosa genes on 1) bacterial acquisition and retention in GWSS foreguts, and 2) transmission to grapevines by GWSS. Bacterial genotypes used were: mutants Xf-ΔpilG, Xf-ΔpilH, Xf-ΔgacA, and Xf-ΔpopP; plus wild type (WT) as control. Results showed that Xf-ΔpilG had enhanced colonization rate and larger numbers in GWSS compared with WT. Yet, Xf-ΔpilG exhibited the same transmission efficiency as WT. The Xf-ΔpilH exhibited poor acquisition and retention. Although initial adhesion, multiplication, and retention of Xf-ΔpilH in GWSS were almost eliminated compared with WT, the mutation did not reduce transmission success in grapevines. Overall, Xf-ΔgacA showed colonization rates and numbers in foreguts similar to WT. The Xf-ΔgacA mutation did not affect initial adhesion, multiplication, and long-term retention compared with WT, and was not significantly diminished in transmission efficiency. In contrast, numbers of Xf-ΔpopP were variable over time, displaying greatest fluctuation from highest to lowest levels. Thus, Xf-ΔpopP had a strong, negative effect on initial adhesion, but adhered and slowly multiplied in the foregut. Again, transmission was not diminished compared to WT. Despite reductions in acquisition and retention by GWSS, transmission efficiency of genotypes to grapevines was not affected. Therefore, in order to stop the spread of X. fastidiosa by GWSS using gene-level targets, complete disruption of bacterial colonization mechanisms is required.
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Anterior Foregut Microbiota of the Glassy-Winged Sharpshooter Explored Using Deep 16S rRNA Gene Sequencing from Individual Insects
2016Co-Authors: Elizabeth E. Rogers, Elaine A. BackusAbstract:The Glassy-Winged Sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of Sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the Sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-si
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Anterior foregut microbiota of the Glassy-Winged Sharpshooter explored using deep 16S rRNA gene sequencing from individual insects.
PloS one, 2014Co-Authors: Elizabeth E. Rogers, Elaine A. BackusAbstract:The Glassy-Winged Sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of Sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the Sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony), were characterized for bacteria in dissected Sharpshooter cibaria and precibaria by amplification and sequencing of a portion of the 16S rRNA gene using Illumina MiSeq technology. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; sequencing of the Wolbachia ftsZ gene placed this strain in supergroup B, one of two Wolbachia supergroups most commonly associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia) and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas). Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. Many of these species likely interact with X. fastidiosa in the cibarium and precibarium.
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Salivary enzymes are injected into xylem by the Glassy-Winged Sharpshooter, a vector of Xylella fastidiosa.
Journal of insect physiology, 2012Co-Authors: Elaine A. Backus, Kim B. Andrews, Holly J. Shugart, L. Carl Greve, John M. Labavitch, Hasan AlhaddadAbstract:A few phytophagous hemipteran species such as the Glassy-Winged Sharpshooter, Homalodisca vitripennis, (Germar), subsist entirely on xylem fluid. Although poorly understood, aspects of the insect’s salivary physiology may facilitate both xylem-feeding and transmission of plant pathogens. Xylella fastidiosa is a xylem-limited bacterium that causes Pierce’s disease of grape and other scorch diseases in many important crops. X. fastidiosa colonizes the anterior foregut (precibarium and cibarium) of H. vitripennis and other xylem-feeding vectors. Bacteria form a dense biofilm anchored in part by an exopolysaccharide (EPS) matrix that is reported to have a b-1,4-glucan backbone. Recently published evidence supports the following, salivation-egestion hypothesis for the inoculation of X. fastidiosa during vector feeding. The insect secretes saliva into the plant and then rapidly takes up a mixture of saliva and plant constituents. During turbulent fluid movements in the precibarium, the bacteria may become mechanically and enzymatically dislodged; the mixture is then egested back out through the stylets into plant cells, possibly including xylem vessels. The present study found that proteins extracted from dissected H. vitripennis salivary glands contain several enzyme activities capable of hydrolyzing glycosidic linkages in polysaccharides such as those found in EPS and plant cell walls, based on current information about the structures of those polysaccharides. One of these enzymes, a b-1,4-endoglucanase (EGase) was enriched in the salivary gland protein extract by subjecting the extract to a few, simple purification steps. The EGase-enriched extract was then used to generate a polyclonal antiserum that was used for immunohistochemical imaging of enzymes in Sharpshooter salivary sheaths in grape. Results showed that enzymecontaining gelling saliva is injected into xylem vessels during Sharpshooter feeding, in one case being carried by the transpiration stream away from the injection site. Thus, the present study provides support for the salivation-egestion hypothesis. Published by Elsevier Ltd.
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A new Phytoreovirus infecting the Glassy-Winged Sharpshooter (Homalodisca vitripennis).
Virology, 2009Co-Authors: Drake C. Stenger, Mark S. Sisterson, Rodrigo Krugner, Elaine A. Backus, Wayne B. HunterAbstract:A new virus species of the genus Phytoreovirus was isolated from Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in California and designated here as Homalodisca vitripennis reovirus (HoVRV). Extraction of nucleic acid from GWSS adults collected from three Californian populations revealed an array of double-stranded (ds) RNA species that was soluble in 2 M LiCl and resistant to degradation upon exposure to S1 nuclease and DNase. Analysis of nucleic acid samples from single GWSS adults indicated that HoVRV dsRNA accumulated to high titer in individual insects. Double-shelled isometric virus particles purified from GWSS adults resembled those observed in thin sections of GWSS salivary glands by transmission electron microscopy. Purified HoVRV virions contained 12 dsRNA segments that, based on complete nucleotide sequences, ranged in size from 4475 to 1040 bp. Sequence comparisons indicated that the HoVRV dsRNA segments were most closely related (58.5 to 43.7% nt sequence identity) to the corresponding genome segments of Rice dwarf virus (RDV). Each HoVRV dsRNA segment encoded a single open reading frame (>300 nts) except for segment 11, which appears to be dicistronic. Terminal nucleotide sequences of HoVRV positive-sense RNAs were similar to other phytoreoviruses (GGCG or GGCA at the 5'-end and UGAU or CGAU at the 3'-end) with adjacent imperfect inverted repeats potentially able to base pair. Phylogenetic analyses of the RNA-directed RNA polymerase (encoded by segment 1) and the outer capsid protein (encoded by segment 8) confirmed placement of HoVRV as a species of the genus Phytoreovirus sharing a most recent common ancestor with RDV. Reverse transcription-polymerase chain reaction assays revealed that HoVRV infection of GWSS in California was common and that the virus also occurred in GWSS populations from the Carolinas and Texas.
Thomas A. Miller - One of the best experts on this subject based on the ideXlab platform.
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A paratransgenic strategy to block transmission of Xylella fastidiosa from the Glassy-Winged Sharpshooter Homalodisca vitripennis
BMC Biotechnology, 2018Co-Authors: Arinder K. Arora, Verónica Quintero-hernández, Kendra N Pesko, Thomas A. Miller, Raghu V. DurvasulaAbstract:BackgroundArthropod-borne diseases remain a leading cause of human morbidity and mortality and exact an enormous toll on global agriculture. The practice of insecticide-based control is fraught with issues of excessive cost, human and environmental toxicity, unwanted impact on beneficial insects and selection of resistant insects. Efforts to modulate insects to eliminate pathogen transmission have gained some traction and remain future options for disease control.ResultsHere, we report a paratransgenic strategy that targets transmission of Xylella fastidiosa, a leading bacterial pathogen of agriculture, by the Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis. Earlier, we identified Pantoea agglomerans, a bacterial symbiont of the GWSS as the paratransgenic control agent. We genetically engineered P. agglomerans to express two antimicrobial peptides (AMP)-melittin and scorpine-like molecule (SLM). Melittin and SLM were chosen as the effector molecules based on in vitro studies, which showed that both molecules have anti-Xylella activity at concentrations that did not kill P. agglomerans. Using these AMP-expressing strains of P. agglomerans, we demonstrated disruption of pathogen transmission from insects to grape plants below detectable levels.ConclusionThis is the first report of halting pathogen transmission from paratransgenically modified insects. It is also the first demonstration of paratransgenic control in an agriculturally important insect vector.
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a paratransgenic strategy to block transmission of xylella fastidiosa from the glassy winged Sharpshooter homalodisca vitripennis
BMC Biotechnology, 2018Co-Authors: Arinder K. Arora, Kendra N Pesko, Thomas A. Miller, Veronica Quinterohernandez, Lourival D Possani, Raghu V. DurvasulaAbstract:Arthropod-borne diseases remain a leading cause of human morbidity and mortality and exact an enormous toll on global agriculture. The practice of insecticide-based control is fraught with issues of excessive cost, human and environmental toxicity, unwanted impact on beneficial insects and selection of resistant insects. Efforts to modulate insects to eliminate pathogen transmission have gained some traction and remain future options for disease control. Here, we report a paratransgenic strategy that targets transmission of Xylella fastidiosa, a leading bacterial pathogen of agriculture, by the Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis. Earlier, we identified Pantoea agglomerans, a bacterial symbiont of the GWSS as the paratransgenic control agent. We genetically engineered P. agglomerans to express two antimicrobial peptides (AMP)-melittin and scorpine-like molecule (SLM). Melittin and SLM were chosen as the effector molecules based on in vitro studies, which showed that both molecules have anti-Xylella activity at concentrations that did not kill P. agglomerans. Using these AMP-expressing strains of P. agglomerans, we demonstrated disruption of pathogen transmission from insects to grape plants below detectable levels. This is the first report of halting pathogen transmission from paratransgenically modified insects. It is also the first demonstration of paratransgenic control in an agriculturally important insect vector.
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Detection of the bacterium, Xylella fastidiosa, in saliva of Glassy-Winged Sharpshooter, Homalodisca vitripennis
2015Co-Authors: Jose L. Ramirez, Paulo T. Lacava, Thomas A. MillerAbstract:Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), the Glassy-Winged Sharpshooter, is one of the most important vectors of the bacterium, Xylella fastidiosa subsp. piercei (Xanthomonadales: Xanthomonadaceae) that causes Pierce’s Disease in grapevines in California. In the present study we report a new method for studying pathogen transmission or probing behavior of H. vitripennis. When confined, H. vitripennis attempt to probe the surface of sterile containers 48 hours post-acquisition of X. f. piercei. The saliva deposited during attempted feeding probes was found to contain X. f. piercei. We observed no correlation between X. f. piercei titers in the foregut of H. vitripennis that fed on Xylella-infected grapevines and the presence of this bacterium in the deposited saliva. The infection rate after a 48 h post-acquisition feeding on healthy citrus and grapevines was observed to be 77 % for H. vitripennis that fed on grapevines and 81 % for H. vitripennis that fed on citrus, with no difference in the number of positive probing sites from H. vitripennis that fed on either grapevine or citrus. This method is amenable for individual assessment of X. f. piercei-infectivity, with samples less likel
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ANALYSIS OF THE BACTERIAL COMMUNITY INHABITING Glassy-Winged Sharpshooter FOREGUT BY CULTURE-DEPENDENT TECHNIQUES AND DGGE
2015Co-Authors: Paulo T. Lacava, Thomas A. Miller, Jennifer Parker, Francisco Dini-andreote, José Luiz. Ramirez, Welington L. Araújo, João Lucio AzevedoAbstract:The Glassy-Winged Sharpshooter (GWSS) is an important vector of Xylella fastidiosa (Xf), the bacterial pathogen that causes several economically important plant diseases, including citrus variegated chlorosis (CVC), oleander leaf scorch (OLS) and Pierce’s disease (PD) of grapevines. In recent years there has been an increasing interest in the potential use of biological control agents to halt the spread of Xf. One such strategy is the exploration of symbiotic microorganisms to reduce the spread of the pathogen (symbiotic control). In a symbiotic control strategy a bacterium symbiont that occupies the same niche as the pathogen must be identified. The study of the bacterial community of GWSS foreguts by isolation and DGGE revealed the presence of several potential symbiotic candidates such as Bacillus sp., Pseudomonas sp., Methylobacterium sp. and Curtobacterium flaccumfaciens (C. flaccumfaciens). Members of genus Methylobacterium and C. flaccumfaciens are frequently isolated as endophytes from citrus plants with CVC symptoms and without disease symptoms. Recently, an interaction between Methylobacterium, C. flaccumfaciens and Xf was strongly indicated, reinforcing that these bacteria could interact inside the host plant and vector insect. In the future, the genus Methylobacterium and C. flaccumfaciens could be an interesting candidate in a strategy of symbiotic control to Xf
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Fate of a Genetically Modified Bacterium in Foregut of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae)
Journal of economic entomology, 2008Co-Authors: Jose Luis Ramirez, Thomas M. Perring, Thomas A. MillerAbstract:Abstract Symbiotic control is a new strategy being investigated to prevent the spread of insect-transmitted pathogens by reducing vector competence. We are developing this strategy to reduce the spread of Xylella fastidiosa by Homalodisca vitripennis (Germar) [formerly Homalodisca coagulata (Say)] (Hemiptera: Cicadellidae), the Glassy-Winged Sharpshooter. In this study, the fate of a transformed symbiotic bacterium, Alcaligenes xylosoxidans variety denitrificans (S1Axd), in the foregut of Glassy-Winged Sharpshooter when fed on citrus (Citrus spp.) and grape (Vitris spp.) was assessed. TaqMan-based quantitative real-time polymerase chain reaction (PCR) was used to detect and quantify bacterial cells remaining in the foregut at 0, 2, 4, 9, and 12 d after acquisition. S1Axd titer dropped rapidly by 2 d after acquisition, but in spite of this, at end of the 12-d experimental period, 45 and 38% of the Glassy-Winged Sharpshooters retained the transformed bacteria, when fed on grape and citrus, respectively.
