scholarly journals 026 The Effect of Temperature on the Development of Fusarium Stem Rot in Greenhouse Peppers in South Florida

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 392D-392
Author(s):  
E.M. Lamb ◽  
R.M Sonoda ◽  
E.F. Oxman ◽  
E.N. Rosskopf
Keyword(s):  
Lesion Size ◽  
South Florida ◽  
Stem Rot ◽  
Effect Of Temperature ◽  
Lesion Length ◽  
Controlled Environment ◽  
Disease Development ◽  
Greenhouse Production ◽  
Disease Symptoms ◽  
Environment Chamber

Hydroponic greenhouse production of sweet peppers is a well-established and growing industry in South Florida. Plants are in the greenhouse from about October until June, and the long season makes disease problems particularly costly to producers. A stem rot caused by Fusarium solani (anamorph of Nectria haematococca) and previously unreported in South Florida was found on greenhouse peppers in March 1999. Black lesions occurred at nodes where the plant was pruned or fruit was harvested. Tissues above the lesion appeared normal until the lesion girdled the stem, at which point the tissues above the lesion wilted and died. Greenhouse surveys over a 4-month period suggested that environmental factors played a role in number of infected plants and lesion size. A controlled environment chamber test was conducted to evaluate the effect of temperature and cultivar on disease development and severity. Three greenhouse pepper cultivars; Cubico, Triple 4, and Kelvin, were stem inoculated with F. solani at the 3- to 4-week stage. Noninoculated plants were included as a control. Fifteen plants of each cultivar plus control plants were incubated at ≈35, 32, and 29 °C for 2 weeks. The test was run twice. All inoculated plants developed lesions while no control plants developed disease symptoms. Lesion length and diameter were measured for all plants and wilting associated with disease development was noted. Temperature had a significant effect on disease severity with larger lesions and more frequent wilting occurring at higher temperatures. Cultivar did not affect the development of the disease.

Effect of Temperature on Response of Tomatoes to Several Dinitroaniline Herbicides and Phosphorus

Weed Science ◽  
1976 ◽  
Vol 24 (1) ◽  
pp. 115-119 ◽  
Author(s):  
H. P. Wilson ◽  
F. B. Stewart ◽  
T. E. Hines
Keyword(s):  
High Temperatures ◽  
Phosphorus Content ◽  
Dry Weight ◽  
Field Studies ◽  
Effect Of Temperature ◽  
Controlled Environment ◽  
Effects Of Temperature ◽  
Environment Chamber ◽  
Chamber Studies ◽  
Dinitroaniline Herbicides

Effects of temperature on response of transplanted tomatoes (Lycopersicon esculentumMill. ‘Campbell 17′) to trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], and isopropalin (2,6-dinitro-N,N-dipropylcumidine) were investigated in field studies. Trifluralin and nitralin caused greater reductions in growth and yields of tomatoes transplanted early in April than to tomatoes transplanted around May 1. Responses to profluralin were similar but total yields of early transplanted tomatoes were not reduced although initial yields were below those of tomatoes treated with isopropalin. In controlled environment chamber studies, percent phosphorus of plant tops was reduced by trifluralin at low temperatures but was not influenced by trifluralin at high temperatures. Tomoto responses to phosphorus as reflected by plant fresh weight, dry weight and phosphorus content (mg/plant) were reduced by trifluralin at low and high temperatures.

scholarly journals Hyperlocal Variation in Soil Iron and Rhizosphere Microbiome Determines Disease Development in Amenity Turfgrass

2020 ◽  
Author(s):  
Ming-Yi Chou ◽  
Smita Shrestha ◽  
Renee Rioux ◽  
Paul Koch
Keyword(s):  
Soil Properties ◽  
Bulk Soil ◽  
Controlled Environment ◽  
Rrna Gene ◽  
Disease Development ◽  
Dollar Spot ◽  
Rhizosphere Microbiome ◽  
Environment Chamber ◽  
Plant Pathosystems ◽  
Important Disease

ABSTRACTDollar spot, caused by the fungal pathogen Clarireedia spp., is an economically important disease of amenity turfgrass in temperate climates worldwide. This disease often occurs in a highly variable manner, even on a local scale with relatively uniform environmental conditions. The objective of this study was to investigate mechanisms behind this local variation, focusing on contributions of the soil and rhizosphere microbiome. Turfgrass, rhizosphere, and bulk soil samples were taken from within a 256 m2 area of healthy turfgrass, transported to a controlled environment chamber, and inoculated with C. jacksonii. Bacterial communities were profiled targeting the 16s rRNA gene, and 16 different soil chemical properties were assessed. Despite their initial uniform appearance, the samples differentiated into highly susceptible and moderately susceptible groups following inoculation in the controlled environment chamber. The highly susceptible samples harbored a unique rhizosphere microbiome with lower relative abundance of antibiotic-producing bacterial taxa and higher predicted abundance of genes associated with xenobiotic biodegradation pathways. In addition, stepwise regression revealed that bulk soil iron content was the only significant soil characteristic that positively regressed with decreased dollar spot susceptibility during the peak disease development stage. These findings suggest that localized variation in soil iron induces the plant to select for a particular rhizosphere microbiome that alters the disease outcome. More broadly, further research in this area may indicate how plot-scale variability in soil properties can drive variable plant disease development through alterations in the rhizosphere microbiome.IMPORTANCEDollar spot is the most economically important disease of amenity turfgrass, and more fungicides are applied targeting dollar spot than any other turfgrass disease. Dollar spot symptoms are small (3-5 cm), circular patches that develop in a highly variable manner within plot-scale even under seemingly uniform conditions. The mechanism behind this variable development is unknown. This study observed that differences in dollar spot development over a 256 m2 area were associated with differences in bulk soil iron concentration and correlated with a particular rhizosphere microbiome. These findings provide important clues for understanding the mechanisms behind the highly variable development of dollar spot, which may offer important clues for innovative control strategies. Additionally, these results also suggest that small changes in soil properties can alter plant activity and hence the plant-associated microbial community which has important implications for a broad array of important agricultural and horticultural plant pathosystems.

scholarly journals First Report of Pythium paroecandrum on Lupinus havardii

Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 880-880
Author(s):  
S. P. Fernández-Pavía ◽  
M. Valenzuela-Vazquez
Keyword(s):  
Irrigation System ◽  
Growing Season ◽  
Stem Rot ◽  
Greenhouse Production ◽  
Koch’S Postulates ◽  
Disease Symptoms ◽  
First Report ◽  
Big Bend ◽  
Genus Pythium ◽  
Koch's Postulates

Lupinus havardii Wats. (Big Bend Bluebonnet), a plant native to Texas, has been tested extensively for greenhouse production as a cutflower crop (1). Disease symptoms were observed on L. havardii plants grown in Las Cruces, NM, during two consecutive years. Plants were grown in Metro Mix 200 and watered by an automatic irrigation system every 3 days. During the growing season, which extended from September through February, 6% of mature plants (10-week-old plants) became chlorotic, wilted, and died. The first symptoms were observed during December 1998, when greenhouse temperatures were from 10 to 13°C. During the rest of the growing season, from February to July, only one plant became diseased, during May 1999, and the plant died within 1 week after greenhouse temperatures reached 20 to 25°C. Diseased plants were examined, and root, crown, and stem rot were found. Pythium paroecandrum Drechs. (2) was isolated routinely from infected tissues. Koch's postulates were fulfilled after plants were inoculated with oospores and mycelia of P. paroecandrum. Inoculum was applied next to the crown of 6-week-old plants in the form of water-agar plugs and a suspension that contained P. paroecandrum oospores and mycelia. Plants were maintained at 20 to 25°C. After 10 days, symptoms were similar to those previously observed, and the pathogen was reisolated from necrotic lesions observed on stems and crowns. Disease developed slower on 6-week-old plants (inoculated) than on 10-week-old plants (naturally infected). This is the first report of P. paroecandrum on L. havardii. References: (1) W. A. Mackay and T. D. Davis. HortScience 33:348, 1998. (2) A. J. Van der Plaats-Niterink. Monograph of the genus Pythium. Studies Mycol. 21:1, 1981.

scholarly journals Silicon Alleviates the Disease Severity of Sclerotinia Stem Rot in Rapeseed

2021 ◽  
Vol 12 ◽  
Author(s):  
Yuxia Feng ◽  
Yuxin Hu ◽  
Pengpeng Fang ◽  
Xiangjun Zuo ◽  
Jinxiong Wang ◽  
...  
Keyword(s):  
Disease Severity ◽  
Seed Quality ◽  
Agronomic Traits ◽  
Induced Defense ◽  
Disease Incidence ◽  
Defense Responses ◽  
Lesion Size ◽  
Stem Rot ◽  
Lesion Length ◽  
Sclerotinia Stem Rot

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a devastating disease in rapeseed. The objective of this study was to investigate the role and the mechanism of silicon (Si) in alleviating the disease severity of S. sclerotiorum in rapeseed. In the absorption assays, the rapeseed that absorbed 10 mM of K2SiO3 exhibited an 86% decrease in lesion size on infected leaves as compared with controls. In the spray assay, the lesion length on rapeseed stems was reduced by 30.5–32.9% with the use of 100 mM of a foliar Si fertilizer as compared with controls. In the pot assay, the lesion length on rapeseed stems was reduced by 34.9–38.3% when using the Si fertilizer as basal fertilizer. In the field assay, both the disease incidence and disease index of sclerotinia stem rot were significantly reduced with the usage of a solid Si fertilizer, Si foliar fertilizer, and the application of both, without negative affection on the main agronomic traits and seed quality of rapeseed. The transcriptome sequencing, quantitative reverse transcription PCR (qRT-PCR), and biochemical assays between K2SO4- and K2SiO3- treated rapeseed leaves revealed that Si promoted the biosynthesis of defense-related substances and enhanced the antioxidation and detoxification abilities of rapeseed after infection. Thus, this study concluded that Si can alleviate the disease severity of S. sclerotiorum in rapeseeds, partially due to the induced defense responses.

scholarly journals Hyperlocal Variation in Soil Iron and the Rhizosphere Bacterial Community Determines Dollar Spot Development in Amenity Turfgrass

2021 ◽  
Vol 87 (10) ◽  
Author(s):  
Ming-Yi Chou ◽  
Smita Shrestha ◽  
Renee Rioux ◽  
Paul Koch
Keyword(s):  
Soil Properties ◽  
Iron Concentration ◽  
Bulk Soil ◽  
Controlled Environment ◽  
Rrna Gene ◽  
Disease Development ◽  
Dollar Spot ◽  
Rhizosphere Microbiome ◽  
Environment Chamber ◽  
Plant Pathosystems

ABSTRACT Dollar spot, caused by the fungal pathogen Clarireedia spp., is an economically important foliar disease of amenity turfgrass in temperate climates worldwide. This disease often occurs in a highly variable manner, even on a local scale with relatively uniform environmental conditions. The objective of this study was to investigate mechanisms behind this local variation, focusing on contributions of the soil and rhizosphere microbiome. Turfgrass, rhizosphere, and bulk soil samples were collected from within a 256-m2 area of healthy turfgrass, transported to a controlled environment chamber, and inoculated with Clarireedia jacksonii. Bacterial communities were profiled by targeting the 16S rRNA gene, and 16 different soil chemical properties were assessed. Despite their initial uniform appearance, the samples differentiated into highly susceptible and moderately susceptible groups following inoculation in the controlled environment chamber. The highly susceptible samples harbored a unique rhizosphere microbiome with suggestively lower relative abundance of putative antibiotic-producing bacterial taxa and higher predicted abundance of genes associated with xenobiotic biodegradation pathways. In addition, stepwise regression revealed that bulk soil iron content was the only significant soil characteristic that positively regressed with decreased dollar spot susceptibility during the peak disease development stage. These findings suggest that localized variation in soil iron induces the plant to select for a particular rhizosphere microbiome that alters the disease outcome. More broadly, further research in this area may indicate how plot-scale variability in soil properties can drive variable plant disease development through alterations in the rhizosphere microbiome. IMPORTANCE Dollar spot is the most economically important disease of amenity turfgrass, and more fungicides are applied targeting dollar spot than any other turfgrass disease. Dollar spot symptoms are small (3 to 5 cm), circular patches that develop in a highly variable manner within plot scale even under seemingly uniform conditions. The mechanism behind this variable development is unknown. This study observed that differences in dollar spot development over a 256-m2 area were associated with differences in bulk soil iron concentration and correlated with a particular rhizosphere microbiome. These findings provide interesting avenues for future research to further characterize the mechanisms behind the highly variable development of dollar spot, which may inform innovative control strategies. Additionally, these results suggest that small changes in soil properties can alter plant activity and hence the plant-associated microbial community, which has important implications for a broad array of agricultural and horticultural plant pathosystems.

TOLERANCE OF EARLY-MATURING SOYBEAN CULTIVARS TO METRIBUZIN

1986 ◽  
Vol 66 (1) ◽  
pp. 125-130 ◽  
Author(s):  
G. H. FRIESEN ◽  
D. A. WALL
Keyword(s):  
Sandy Loam ◽  
Controlled Environment ◽  
Clay Loam ◽  
Clay Loam Soil ◽  
Soybean Cultivars ◽  
Early Maturing ◽  
Glycine Max L ◽  
Loam Soil ◽  
Environment Chamber ◽  
Chamber Studies

McCall, Maple Presto, Maple Amber and OT80-3 soybean (Glycine max (L.) Merr.) cultivars were evaluated under field conditions for their response to metribuzin. Maple Amber was found to be less tolerant than the other cultivars. In controlled environment chamber studies, injury to this cultivar was more severe on a sandy loam soil than on a clay loam soil. Fall applications of metribuzin, alone or tank-mixed with trifluralin, were tolerant to Maple Amber soybeans and such applications may offer a practical alternative to spring treatments for broad spectrum weed control in the less tolerant soybean cultivars grown in Manitoba.Key words: Metribuzin, trifluralin, preplant incorporation, fall treatments, soybean cultivars

Humidity Effects on Porous Silica Thin Films

1995 ◽  
Vol 411 ◽  
Author(s):  
J. R. Kokan ◽  
R. A. Gerhardt
Keyword(s):  
Thin Films ◽  
Ac Conductivity ◽  
Sol Gel ◽  
Porous Silica ◽  
Controlled Environment ◽  
Alkali Ions ◽  
Humidity Effects ◽  
Silica Thin Films ◽  
Environment Chamber ◽  
Humidity Sensitivity

ABSTRACTImpedance Spectroscopy is being used to study the humidity sensitivity of porous silica thin films. The films are processed via a colloidal sol-gel method which leaves some remnant potassium and sodium. Previous work on bulk porous silica samples processed by the same method showed that the dielectric properties and ac conductivity were very sensitive to changes in humidity. The aim of this work was to determine if the same dependencies could be found in the thin films. The capacitance, dielectric loss, and ac conductivity of the films were measured in a controlled environment chamber from 20–80% RH for frequencies ranging from 10Hz–10MHz. In addition to characterizing films with varying amounts of residual alkali ions obtained through leaching, we have also measured films that were surface doped with controlled amounts of KCl, LiCl, or NaCl. Relative humidity dependencies in the films are not as dramatic as in the bulk samples. The reasons for this behavior are not yet clear, but may be associated with the porosity, thickness, and surface area of the films.

Host range of Puccinia xanthii and postpenetration development on Xanthium occidentale

1993 ◽  
Vol 71 (7) ◽  
pp. 959-965 ◽  
Author(s):  
Louise Morin ◽  
Bruce A. Auld ◽  
John F. Brown
Keyword(s):  
Key Words ◽  
Host Range ◽  
Weed Control ◽  
Biological Weed Control ◽  
Controlled Environment ◽  
Globe Artichoke ◽  
Disease Symptoms ◽  
Severity Of The Disease ◽  
Stem Lesions ◽  
Slow Growing

In glasshouse studies, small necrotic foliar flecks developed on globe artichoke, calendula, slender thistle, and winged slender thistle following inoculation with basidiospores of the microcyclic rust Puccinia xanthii. Fourteen inoculated cultivars of sunflower developed various types of symptoms: small necrotic and chlorotic flecks, underdeveloped telia, and small swollen petiole and stem lesions. Xanthium spinosum developed very slow-growing telia. In controlled environment studies, the four Xanthium spp. comprising the Noogoora burr (cocklebur) complex in Australia were highly susceptible to infection by P. xanthii. Maximum disease severity was observed after rust telia and X. occidentale plants were exposed to a dew period of 24 h. Less disease symptoms were observed in plants exposed to shorter (3, 6, 12 h) or longer (36 h) dew periods. Plants inoculated with several loads of inoculum (exposure to four inoculum plates) were less diseased than plants inoculated with fewer inoculum loads. Infected plants began to develop disease symptoms 5 days after inoculation, when grown at 25 °C. Infected plants developed very few small chlorotic flecks and no disease symptoms when grown at 10 and 40 °C, respectively. The flecks produced on plants kept at 10 °C developed into telia when plants were transferred to a glasshouse (25 °C). Repetitive inoculations of plants for 1 month increased the overall severity of the disease and this resulted in a reduction in plant height. Key words: Xanthium, host range, Puccinia xanthii, biological weed control.

scholarly journals Resistance to Ceratocystis Wilt (Ceratocystis fimbriata) in Parents and Progenies of Eucalyptus grandis x E. urophylla

2010 ◽  
Vol 59 (1-6) ◽  
pp. 99-106 ◽  
Author(s):  
Carla Cristina Gonçalves Rosado ◽  
Lúcio Mauro Da Silva Guimarães ◽  
Miranda Titon ◽  
Douglas Lau ◽  
Leonardo Rosse ◽  
...  
Keyword(s):  
Genetic Gain ◽  
Eucalyptus Grandis ◽  
Lesion Size ◽  
Interspecific Crosses ◽  
Lesion Length ◽  
Ceratocystis Fimbriata ◽  
Resistance Level ◽  
Ceratocystis Wilt ◽  
High Heritability ◽  
High Degree

AbstractCeratocystis wilt, caused by Ceratocystis fimbriata, is one of the most damaging diseases in eucalyptus plantations worldwide. Although there are resistant genotypes, the genetic basis of resistance is still poorly understood. In this paper we studied the resistance level by a stem inoculation experiment of genotypes of Eucalyptus grandis and E. urophylla and estimated the heritability and gains of selection in families derived from controlled interspecific crosses. In both species, highly resistant as well as highly susceptible genotypes to Ceratocystis wilt were found. Out of 21 parents assessed, twelve were resistant and nine susceptible. Estimates of individual narrow (50%) and broad (59%) sense heritability suggested a high degree of genetic control and low allelic dominance of the trait. There was great genetic variation among and within families, a fact that contributes to high heritability and genetic gain. A genetic gain in lesion size of up to -74.4% was obtained from selection of the 50 best clones in the evaluated families, i.e., the mean lesion length in the progeny population can be reduced by 74,4%.

scholarly journals First Report of Stem Rot of Dracaena Caused by Aspergillus niger in Iran

2008 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Mehrdad Abbasi ◽  
Faezeh Aliabadi
Keyword(s):  
Aspergillus Niger ◽  
Stem Rot ◽  
Local Market ◽  
Disease Symptoms ◽  
First Report ◽  
Dracaena Sanderiana

Specimen plants of Dracaena sanderiana showing stem rot symptoms were collected from a local market in Tehran. Aspergillus niger was isolated from all diseased plants. Healthy greenhouse plants were inoculated and developed disease symptoms. The authors were able to isolate A. niger from all inoculated plants. This is believed to be the first report of A. nigercausing stem rot of D. sanderiana in Iran. Accepted for publication 26 November 2007. Published 12 February 2008.

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