Spotted Wilt Research Articles

Interactive Effects of Planting Date and Cultivar on Tomato Spotted Wilt of Peanut.

Field experiments were conducted at Gainesville and Marianna, FL in 2004 and 2005 in which severity of spotted wilt, caused by Tomato spotted wilt virus, and pod yield were compared in six peanut (Arachis hypogaea) cultivars. The six cultivars included the moderately field resistant cultivars ANorden, C-99R, and Georgia Green; the highly field resistant cultivars AP-3 and DP-1; and the susceptible cultivar SunOleic 97R. There were four trials at each location, with four planting dates that ranged from late March to early June. Tomato spotted wilt severity in moderately resistant and susceptible cultivars was lower at Gainesville than at Marianna in both years in moderately resistant and susceptible cultivars. Trends in incidence for the two locations were less evident for AP-3 and DP-1. At Gainesville, there were few differences in tomato spotted wilt severity, and severity ratings were similar for Georgia Green and SunOleic 97R in two of four trials in 2004 and across all trials in 2005. At Marianna, severity ratings were lower for Georgia Green than for SunOleic 97R in six of the eight trials, and severity of tomato spotted wilt was lower for AP-3, C-99R, and DP-1 than for Georgia Green in all eight trials. In 2004, there was a trend toward decreasing severity ratings for Georgia Green and SunOleic 97R with later planting dates, but not for AP-3 or DP-1 at Marianna. Split-plot field experiments were also conducted at Tifton, GA in 2005 through 2007 in which incidence of tomato spotted wilt and pod yield were compared for peanut cultivars AP-3 and Georgia Green across planting dates ranging from late April through late May. Incidence of tomato spotted wilt was lower for AP-3 than for Georgia Green within each planting date of all years, and planting date effects were smaller in AP-3, if observed at all, than in Georgia Green. In most planting dates of all three trials, yields were higher for AP-3 than for Georgia Green. The relationships between yield and planting date were not consistent. These results indicate that the level of field resistance in AP-3 and DP-1 cultivars is sufficient to allow planting in late April without greatly increasing the risk of losses to tomato spotted wilt.

Susceptibility of Thrips palmi Karny Collected from Occurrence Areas of Cucumber Spotted Wilt in Kanagawa Prefecture

Susceptibility of <i>Thrips palmi</i> Karny Collected from Occurrence Areas of Cucumber Spotted Wilt in Kanagawa Prefecture

Field Evaluation of Virginia-Type Peanut Cultivars for Resistance to Tomato Spotted Wilt Virus, Late Leaf Spot, and Stem Rot

Abstract Susceptibility to viral and fungal diseases is a major factor limiting profit in the production of virginia-type peanuts (Arachis hypogaea L.) in the South Carolina coastal plain. Field tests were conducted over a three-year period (2006–08) to evaluate the disease resistance of 47 experimental virginia-type breeding lines and eight cultivars. Relative to commercially available standards, cultivar Bailey (recently released by N. C. State Univ.), three sister lines (N03088T, N03089T, and N03090T), and N03091T were found to have consistently less susceptibility to tomato spotted wilt tospovirus; late leaf spot, Cercosporidium personatum (Berk. and Curt.) Deighton; and stem rot, Sclerotium rolfsii Sacc. The level of field resistance measured for these three diseases was comparable to that of a resistant runner-type cultivar, Georgia-03L. Yield was highly correlated with multiple disease resistance, and yield performance of some resistant lines exceeded the best commercial standard cultivars under reduced fungicide programs. Potential negative attributes of Bailey, its sister lines, and N03091T were a greater susceptibility to leafhopper injury, Empoasca fabae (Harris), and a relatively larger plant size at maturity, without well defined rows to facilitate digging. Other lines that demonstrated reduced susceptibility to both tomato spotted wilt and stem rot were N03005J and N02009. Although only evaluated in the last test year, five Univ. of Florida lines (FLMR7, FLMR9, FLMR12, FLMR14, and FLMR15) and Georgia-08V (recently released by the Univ. of Georgia) also showed some reduction in stem rot susceptibility relative to the standard (cultivar NC-V 11). Equally important, many experimental lines were identified with significantly greater disease susceptibility than current commercial cultivars. Under South Carolina production conditions, these lines would be poor candidates for advancement. Deployment of the multiple disease resistance found in these experimental cultivars offers several potential benefits beyond direct yield improvement: reduction of fungicide input costs for both foliar and soil disease control, prolonging the utility of currently available fungicides, and reduction of weather related harvest risk by allowing earlier initial planting dates.

Influence of Paraquat on Yield and Tomato Spotted Wilt Virus for Georgia-02C and Georgia-03L Peanut

Abstract Paraquat is a common herbicide used in peanut production; however, visible injury and reduced yield have been observed in some instances. Most research regarding paraquat injury on peanut has taken place on cultivars that are no longer available and were more susceptible to tomato spotted wilt virus (TSWV) than current cultivars. Field experiments were conducted over three growing seasons to determine the effect of paraquat on yield and TSWV incidence in two moderately TSWV-resistant cultivars (Georgia-02C and Georgia-03L). Paraquat and paraquat plus bentazon were evaluated against a non-treated control at four application timings [7, 14, 21, and 28 d after ground cracking (DAGC)]. There were no yield differences among herbicide treatments or application timings for Georgia-02C peanut, but there was a treatment interaction with Georgia-03L for yield. The majority of interaction comparisons showed no yield differences, but the non-treated control had higher yields than the herbicide treatments when significance did occur. Yields were similar for the 7 DAGC timing in all comparisons. In all instances when differences occurred for both cultivars, TSWV was higher in non-treated plots than where herbicides were applied. This data supports the use of paraquat in Georgia-02C and Georgia-03L peanut since there is minimal chance of yield reduction and may also reduce TSWV incidence; however, additional studies are required.

'AP-4', a Medium Maturity, Large Seeded Peanut Variety with Resistance to Tomato Spotted Wilt

SS-AGR-324, a 3-page illustrated fact sheet by Barry L. Tillman and Daniel W. Gorbet, describes this peanut variety was released by UF/IFAS in 2007 based on its competitive pod yield and excellent seed grade — total sound mature kernel percentage (TSMK), providing the results of tests in three locations over three years. Published by the UF Department of Agronomy, August 2009.

Impact of Early Spring Weather Factors on the Risk of Tomato Spotted Wilt in Peanut.

Peanut growers in the southeastern United States have suffered significant economic losses due to spotted wilt caused by Tomato spotted wilt virus (TSWV). The virus is transmitted by western flower thrips, Frankliniella occidentalis, and tobacco thrips, F. fusca, and was first reported in the southeast in 1986. The severity of this disease is extremely variable in individual peanut fields, perhaps due to the sensitivity of the vector population to changing weather patterns. The objective of this study was to investigate the impact of early spring weather on spotted wilt risk in peanut. On-farm surveys of spotted wilt severity were conducted in Georgia peanut fields in 1998, 1999, 2002, 2004, and 2005. The percent spotted wilt intensity (%) for cv. Georgia Green was recorded and categorized into three intensity levels: low, moderate, and high. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network for the period between March 1 and April 30. Statistical analysis was conducted to identify weather variables that had significant impact on spotted wilt intensity. The results indicated a high probability of spotted wilt if the number of rain days during March was greater than or equal to 10 days and planting was before 11 May or after 5 June. The total evapotranspiration in April (>127 mm) and the average daily minimum temperature in March (>6.8°C) similarly increased the risk of spotted wilt. Knowing in advance the level of spotted wilt risk expected in a peanut field could assist growers with evaluating management options and significantly improve the impact of their decisions against spotted wilt risk in peanut.

Requirements for ER‐Arrest and Sequential Exit to the Golgi of Tomato Spotted Wilt Virus Glycoproteins

The envelope glycoproteins Gn and Gc are major determinants in the assembly of Tomato spotted wilt virus (TSWV) particles at the Golgi complex. In this article, the ER-arrest of singly expressed Gc and the transport of both glycoproteins to the Golgi upon coexpression have been analyzed.While preliminary results suggest that the arrest of Gc at the ER (endoplasmic reticulum) did not appear to result from improper folding, transient expression of chimeric Gc, in which the transmembrane domain (TMD) and/or cytoplasmic tail (CT) were swapped for those from Gn, showed that the TMD of Gn was sufficient to allow ER exit and transport to the Golgi. Expression of both glycoproteins in the presence of overexpressed Sar1p specific guanosine nucleotide exchange factor Sec12p, resulted in ER-retention demonstrating that the viral glycoproteins are transported to the Golgi in a COPII (coat protein II)-dependent manner. Inhibition of ER Golgi transport by brefeldin A (BFA) had a similar effect on the localization of Gn. However, inhibition of ER (endoplasmic reticulum) to Golgi transport of coexpressed Gc and Gn by overexpression of Sec12p or by BFA revealed distinct localization patterns, i.e. diffuse ER localization versus concentration at specific spots.

‘Florida-07’, a Medium Maturity, Large Seeded, High Oleic Peanut Variety with Resistance to Tomato Spotted Wilt

SS-AGR-313, a 3-page fact sheet by B.L. Tillman and D.W. Gorbet, describes this variety of peanut released in 2006 because of its outstanding pod-yield potential, competitive grades, high oleic oil chemistry. Includes a table detailing the performance of runner market-type peanut varieties in Florida locations in the past four years. Published by the UF Department of Agronomy, November 2008. Reviewed May 2012.

Occurrence ofThrips tabacilarvae on TSWV host weeds in the surroundings of sweet pepper greenhouses

The relationship between virus, host plant and vector species is of primary importance for understanding the development of Tomato Spotted Wilt Virus (TSWV) epidemics. One of the vectors, Thrips tabaci , occurs in Hungarian greenhouses and their surroundings all year round. From June 2005 to May 2007 we conducted studies on weed hosts growing in the vicinity of sweet pepper greenhouses in order to know on which TSWV host weeds the larvae develop in different seasons. Of the 16 TSWV host weeds collected Stellaria media proved to be the most frequent weed species with the greatest abundance and it occurred the whole year round at all five investigated locations. Together with Galinsoga parviflora , which had the highest number of T. tabaci larvae in autumn, S. media is very probably the main source of TSWV for epidemics in greenhouses.

Tomato spotted wilt virus nucleocapsid protein interacts with both viral glycoproteins Gn and Gc in planta

Recently, the Tomato Spotted Wilt Virus (TSWV) Gn and Gc glycoproteins were shown to induce the formation of (pseudo-) circular and pleomorphic membrane structures upon transient expression in plant cells. Furthermore, when singly expressed, Gc retains in the ER, while Gn is able to further migrate to the Golgi. Upon co-expression, Gn rescues Gc and co-migrates to the Golgi complex. Here, we have studied the behavior of the glycoproteins in the presence of the viral nucleocapsid (N) protein and in vivo analyzed the occurrence of protein–protein interactions by fluorescence life time imaging microscopy (FLIM). The analysis demonstrated that N co-localizes and interacts with both glycoproteins, with a preference for Gn. Additionally, it is shown that N causes a dramatic change in the distribution of Gc within the ER, from reticular to punctate spots. The observations are discussed in the context of the virus particle formation during the infection process.

Variation Among Virginia Market-Type Peanut Genotypes in Susceptibility to Tomato Spotted Wilt Virus Vectored by Thrips (Thysanoptera: Thripidae)

Abstract Tomato spotted wilt virus (TSWV), a thrips-vectored tospovirus, is an important pathogen of peanut (Arachis hypogaea L.). Development of tolerant cultivars has proven to be one of the most promising methods to manage the disease. Twenty-four genotypes of virginia market-type peanut were monitored in field tests for thrips damage, and TSWV incidence and severity during 2004 and 2005 in North Carolina. The cultivar Gregory had a higher density of adult thrips in foliage than any other genotype, while breeding lines N01057 and N03054E had the lowest density. No significant correlation was detected between thrips density or injury and TSWV incidence. Line N03036EJ had the greatest TSWV incidence, but did not differ from cultivars Gregory or Perry in incidence. Line N00033 had the least TSWV incidence and differed from the cultivars Gregory and Perry. The occurrence of late-season chlorosis or peanut yellowing death (PYD) was highly correlated with TSWV infection (P &amp;lt; 0.0001). Breeding line N02051ol had the greatest incidence of PYD, but did not differ statistically from Gregory or Perry. Lines N03023EF and N01083 had the least PYD incidence. Plants infected with TSWV not expressing foliar symptoms were found in far greater abundance than plants that were infected and symptomatic. Line N03036EJ had the greatest proportion of infected but asymptomatic plants; line N03054E had the least. Susceptible lines are more likely to become infected, rather than just more likely to show spotted wilt symptoms.

Registration of Peanut Germplasm Line TifGP‐1 with Resistance to the Root‐Knot Nematode and Tomato Spotted Wilt Virus

Registration of Peanut Germplasm Line TifGP‐1 with Resistance to the Root‐Knot Nematode and Tomato Spotted Wilt Virus

The Role of Weeds in the Spread of Tomato Spotted Wilt Virus by Thrips tabaci (Thysanoptera: Thripidae) in Tobacco Crops

AbstractOviposition of Thrips tabaci, larval development and their potential to acquire Tomato spotted wilt virus (TSWV) from infected Amaranthus retroflexus, Datura stramonium, Lactuca serriola, Solanum nigrum and Sonchus oleraceus plants and the ability of the adults to transmit this virus to these weeds and tobacco (Nicotiana tabacum cv. Basmas) were studied. When a T. tabaci female was given an oviposition period of 4 days, an average of 21 larvae were produced on leaves of D. stramonium, 17.5 on S. nigrum, 16.3 on L. serriola and 14.3 on S. oleraceus. Significantly higher numbers of larvae were found on tobacco (29.5), and lower numbers on A. retroflexus (1.9). In a choice test, when females were placed onto leaves of these weed species and tobacco in a Petri dish, D. stramonium was preferred over tobacco. Equal numbers of larvae emerged on leaves of tobacco, of L. serriola and of S. nigrum. Oviposition was lower on A. retroflexus and S. oleraceus in this test. After the transfer of newborn 24 h old larvae to leaf discs of tobacco or to one of the weeds 87, 84, 82, 71, 64 and 17% became pupa on tobacco, D. stramonium, L. serriola, S. nigrum, A. retroflexus or S. oleraceus respectively. After acquisition of virus by newborn‐24 h old larvae from L. serriola, D. stramonium, S. nigrum and A. retroflexus 69.5, 51.4, 32.6 and 22% of the adults became transmitters. No transmission could be recorded on S. oleraceus due to a high larval mortality. Males appeared to be more efficient transmitters than females. Tobacco was more susceptible to TSWV than petunia and the weed species, while among weeds, S. nigrum was the most and A. retroflexus the least susceptible species.

AFLP and SCAR Markers Linked to Tomato Spotted Wilt Virus Resistance in Tobacco

Tomato spotted wilt virus (TSWV) is a serious disease in tobacco (Nicotiana tabacum L.). The breeding line ‘Polalta’ contains a single dominant gene conferring resistance to TSWV that was introgressed from N. alata Link &amp; Otto. The resistance is tightly associated with an abnormal plant type, however, and traditional backcrossing has been ineffective in producing normal plants with TSWV resistance. A potential strategy to overcome this problem is to use molecular markers to select against alien chromatin in backcross progeny. Amplified fragment length polymorphism (AFLP) technology and bulked segregant analysis were applied to identify markers linked to the resistance gene. The DNA bulks from susceptible and resistant doubled haploid lines derived from a cross between susceptible cultivar K326 and Polalta were analyzed to identify linked markers. An F2 population and the doubled haploids were used to construct a 2.5‐cM map of this locus containing 17 coupling phase and seven repulsion phase markers. By selecting for resistant plants with an improved plant type and marker profile in a BC3 population, four plants were identified that were missing 1 to 14 of the AFLP markers associated with the alien chromatin, demonstrating that rare recombination events can be identified. Four AFLP fragments were successfully converted to sequence characterized amplified region markers suitable for large‐scale screening. This approach may facilitate development of TSWV‐resistant tobacco cultivars.

Role of Insecticides in Reducing Thrips Injury to Plants and Incidence of Tomato Spotted Wilt Virus in Virginia Market-Type Peanut

Role of Insecticides in Reducing Thrips Injury to Plants and Incidence of Tomato Spotted Wilt Virus in Virginia Market-Type Peanut

Role of Insecticides in Reducing Thrips Injury to Plants and Incidence of Tomato Spotted Wilt Virus in Virginia Market-Type Peanut

Tomato spotted wilt virus (family Bunyaviridae, genus Tospovirus, TSWV), transmitted by many thrips species, is a devastating pathogen of peanut, Arachis hypogaea L. TSWV has become a serious problem in the Virginia/Carolina peanut-growing region of the United States. During 2002, TSWV was present in 47% of the North Carolina hectarage and caused a 5% yield reduction in Virginia. Factors influencing levels of TSWV in runner market-type peanut cultivars, which are primarily grown in Alabama, Flordia, Georgia, and Texas, have been integrated into an advisory to help those peanut growers reduce losses. An advisory based on the southeast runner market-type version is currently under development for virginia market-type peanut cultivars that are grown primarily in the Virginia/ Carolina region. A version based on preliminary field experiments was released in 2003. One factor used in both advisories relates to insecticide use to reduce the vector populations and disease incidence. This research elucidated the influence of insecticides on thrips populations, thrips plant injury, incidence of TSWV, and pod yield in virginia market-type peanut. Eight field trials from 2003 to 2005 were conducted at two locations. In-furrow application of aldicarb and phorate resulted in significant levels of thrips control, significant reductions in thrips injury to seedlings, reduced incidence of TSWV, and significant increases in pod yield. Foliar application of acephate after aldicarb or phorate applied in the seed furrow further reduced thrips plant injury and incidence of TSWV and improved yield. These findings will be used to improve the current virginia market-type TSWV advisory.

Reaction of Peanut Cultivars to Tomato Spotted Wilt Virus (TSWV) Under Field Conditions and Their Response to Mechanical Inoculation by TSWV Under Greenhouse Conditions

Spotted wilt virus disease caused by Tomato spotted wilt tospovirus (TSWV) has become a limiting factor in peanut (Arachis hypogaea L.) production in the Southwest region of the U.S. Selected peanut cultivars (Okrun, Southwest Runner, Tamrun-98, Tamrun-96, Georgia Green, Tamrun OL-02, Tamrun OL-01, and Georgia Hi Oleic) were evaluated for reaction to TSWV in field plots in 2001, 2002, and 2003. Field plots were located near Pearsall, TX, where TSWV is endemic. In 2001, at 72 days post planting (DPP), incidence of TSWV was significantly (P , 0.05) higher in Southwest runner, Okrun, and Tamrun98 than the other cultivars except Tamrun OL-02 in the test. In 2002, disease incidence of TSWV was low and thus only one reading was taken at 135 DPP where the cultivars Georgia Green and Georgia Hi Oleic exhibited the least incidence of spotted wilt. In 2003, at 58 DPP, Georgia Green, and Georgia Hi Oleic showed the lowest incidence of spotted wilt compared with other cultivars. The response of the eight peanut cultivars to TSWV following mechanical inoculation with TSWV at three plant ages was evaluated under greenhouse conditions. Disease severity index (DSI) and plant growth parameters such as root length, root volume, plant height, and fresh weight were determined. ELISA values (as indicative of the relative presence of TSWV), and relative water content were also determined to show the impact of TSWV infections in inoculated plants. Reductions in most plant growth parameters were observed when plants were inoculated with TSWV at five days post-planting, than twelve and nineteen days post-planting inoculation. Positive values of correlation coefficient (CC) between DSI and root volume or root length in the cultivars Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 indicate resistance or tolerance to mechanical inoculation with TSWV. Negative values of CC between DSI and root length or root volume in the cultivars Tamrun-98, Tamrun OL-02, Southwest Runner, and Okrun provide evidence for their susceptibility to TSWV. Comparison of results obtained from the field with those from greenhouse evaluations suggest that Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 cultivars are useful as potential tools for management of TSWV in peanut for the Southwestern United States.

Root Zone Temperature as Modified by Plastic Mulches Affect the Appearance of First Systemic Symptoms of Tomato Spotted Wilt and Fruit Yield in Tomato

Tomato spotted wilt (TSW) is a serious constraint to tomato production in various regions of the world. The effect of TSW on tomato yield is largely influenced by time of infection. Early infection usually results in severe stunting of the seedling and even death of the plant. Plastic mulches have been found to affect both the incidence of TSW, and plant growth and yield of tomato. The objective of this study was to determine the effect of root zone temperature (RZT) as affected by plastic mulch on the timing of appearance of first TSW symptoms, vegetative top fresh weight (FW) and fruit FW in tomato. Under natural TSW infection as well as in artificially inoculated plants, vegetative top FW and fruit FW were both linearly related with number of days after transplanting (DAT) the plants were free from TSW symptoms. The plants grown on black mulch during the fall showed earlier appearance of TSW symptoms, and had significantly reduced vegetative growth and fruit yields. The mean RZT during the first 42 DAT—the time before the plants reached full canopy closure—significantly affected the timing of first appearance of TSW symptoms, tomato plant growth and fruit yield. Vegetative top FW (optimal RZT = 24.1 °C) and fruit FW (26.9 °C) fitted the quadratic relationships with the mean RZT during the first 42 DAT. In conclusion, utilization of plastic mulches that created conditions of RZT stress, particularly heat stress, resulted in reduced plant growth and yield and may predispose the plants to earlier expression of TSW symptoms compared to plants grown under RZTs more favorable to tomato plant growth.

Interactions of Tillage with Management Practices Designed to Minimize Tomato Spotted Wilt of Peanut (Arachis hypogaea L.)

Abstract Conservation tillage is a cultural practice that reduces tomato spotted wilt of peanut (Arachis hypogaea L.) compared with conventional tillage. Other practices that influence incidence of...

Incidence of Thrips and Tomato Spotted Wilt Tospovirus in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations

Incidence of Thrips and Tomato Spotted Wilt Tospovirus in Flue-Cured Tobacco Protected from Early Season Insect Pest Infestations