scholarly journals Influence of Temperature, Relative Humidity, Ascospore Concentration, and Length of Drying of Colonized Dry Bean Flowers on White Mold Development

Plant Disease ◽  
2006 ◽  
Vol 90 (7) ◽  
pp. 946-950 ◽  
Author(s):  
R. Harikrishnan ◽  
L. E. del Río
Keyword(s):  
Relative Humidity ◽  
Linear Increase ◽  
White Mold ◽  
Post Inoculation ◽  
Disease Development ◽  
Dry Bean ◽  
Influence Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Inoculum Type

Growth chamber studies were conducted using rehydrated dry bean (Phaseolus vulgaris) flowers (RDBF) to assess the influence of temperature (18 and 22°C), relative humidity (RH; 25 and 90%), and ascospore concentrations (102, 103, and 104 ascospores/ml) on white mold incidence in dry bean. Additional studies were carried out to determine the influence of inoculum type (ascospore and mycelium) and to estimate the effect of duration of drying of colonized RDBF on viability of Sclerotinia sclerotiorum and white mold incidence. There was a linear increase in white mold incidence with increase in ascospore concentration but neither temperature nor RH levels significantly affected disease development. In the inoculum type study, both temperature and RH levels significantly affected white mold incidence; however, neither ascospore nor mycelial inocula had a significant effect on white mold incidence. Drying colonized RDBF for up to 96 h did not affect S. sclerotiorum viability; but the amount of white mold incidence depended more on post-inoculation RH and drying duration than on the temperatures tested. Colonized RDBF dried for 96 h took approximately three times longer to achieve 100% white mold incidence compared with colonized RDBF dried for 24 h. These results suggest the potential for greater white mold development with higher ascospore availability and the potential of dry S. sclerotiorum-colonized dry bean flowers as a viable inoculum source.

Anthracnose of Florida Beggarweed (Desmodium tortuosum) Caused byColletotrichum truncatum

Weed Science ◽  
1988 ◽  
Vol 36 (3) ◽  
pp. 329-334 ◽  
Author(s):  
John Gardina ◽  
Robert H. Littrell ◽  
Richard T. Hanlin
Keyword(s):  
Relative Humidity ◽  
Host Specificity ◽  
Plant Species ◽  
Fungal Pathogen ◽  
Disease Development ◽  
Colletotrichum Truncatum ◽  
Optimum Conditions ◽  
Cotyledon Stage ◽  
Chamber Studies ◽  
Growth Chamber Studies

Greenhouse and growth chamber studies were conducted to determine conditions for infection of the fungal pathogenColletotrichum truncatum(Schw.) Andrus and Moore on Florida beggarweed (Desmodium tortuosum(Sw.) DC. # DEDTO and to determine the host specificity of this fungus. Optimum conditions for disease development were 14 to 16 h incubation in 100% relative humidity (RH) at 24 to 29 C. Control of Florida beggarweed with 105to 107C. truncatumspores/ml was greatest in the cotyledon stage and decreased with plant age. Ten of 18Desmodiumspecies tested were susceptible to the Florida beggarweed isolate ofC. truncatumbut 13 other plant species and varieties were resistant and 61 were immune.

Efficacy of three greenhouse screening methods for the identification of physiological resistance to white mold in dry bean

2009 ◽  
Vol 89 (4) ◽  
pp. 755-762 ◽  
Author(s):  
H Terán ◽  
S P Singh
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Sclerotinia Sclerotiorum ◽  
Screening Method ◽  
White Mold ◽  
Screening Methods ◽  
Post Inoculation ◽  
Dry Bean ◽  
Physiological Resistance ◽  
Nueva Granada

White mold (WM) caused by Sclerotinia sclerotiorum (Lib.) de Bary is the most devastating disease of common bean (dry and snap or garden bean) (Phaseolus vulgaris L.) in North America. The use of a reliable screening method (SM) in common bean is crucial to improve physiological resistance to WM. The objective of this study was to compare the efficacy of three SM to identify physiological resistance in dry bean genotypes with different evolutionary origins and levels of resistance. Screening methods tested were: (i) the modified straw test or cut–stem (CSM); (ii) infected bean flower (IFL); and (iii) infected oat seed (IOS). A 195, ICA Bunsi, Othello, and VCW 54 dry bean were tested with the three SM. The experimental design was a split plot in randomized complete blocks with three replications in 2007 and 2008. Two independent inoculations 1 wk apart for each SM were made. The WM reaction was scored at 16, 23, and 33 d post-inoculation (DPI) using a 1 to 9 scale. There were highly significant differences between SM and its interaction with years. The CSM and IFL were the most consistent and highly correlated (r > 0.70, P < 0.01). Interspecific breeding line VCW 54 consistently had the highest WM resistance across years, SM, and evaluation dates, followed by A 195. White mold scores increased with delayed evaluations. Thus, CSM or IFL with disease assessed 33 DPI should be used for identifying common bean genotypes with high levels of physiological resistance to WM.Key words: Common bean, growth habit, race Mesoamerica, race Nueva Granada, Phaseolus vulgaris, Sclerotinia sclerotiorum

scholarly journals Factors Affecting Concentrations of Airborne Conidia of Oidium sp. Among Poinsettias in a Greenhouse

Plant Disease ◽  
2000 ◽  
Vol 84 (10) ◽  
pp. 1089-1095 ◽  
Author(s):  
J. M. Byrne ◽  
M. K. Hausbeck ◽  
B. D. Shaw
Keyword(s):  
Relative Humidity ◽  
Rapid Decrease ◽  
Disease Development ◽  
Factors Affecting ◽  
Influence Of Temperature ◽  
Large Numbers ◽  
Airborne Conidia ◽  
Influence Of Temperature On ◽  
Atmospheric Concentrations

Atmospheric concentrations of Oidium sp. conidia in two research greenhouses containing infected poinsettias were monitored to investigate the role of environment in prompting conidial release and dissemination. Hourly concentrations of conidia of Oidium sp. were estimated using a Burkard volumetric spore sampler. The influence of temperature on disease development was studied by placing healthy poinsettias in each greenhouse for 7-day periods, removing them, and recording the days to the appearance of the first colony. When averaged over 5 December to 1 June, atmospheric conidial concentrations in greenhouse (GH) 2 were greatest during 1000 to 1800 hours with a peak (325 conidia/m3/h) occurring at 1200 hours. In GH 11, peak concentrations occurred at 1300 hours (65 conidia/m3/h) and 1600 hours (75 conidia/m3/h). Large numbers of conidia were sampled (≥100/m3) within 1-h periods, indicating conidial release events (CREs). Fluctuations in relative humidity (RH) (either positive or negative) prompted CREs. In both greenhouses, the highest number of CREs (up to 23) occurred following RH fluctuations of 5 to 15%. Watering resulted in an immediate increase (≤25%) followed by a rapid decrease in RH (≤32%) beginning 1 to 2 h later. In GH 2 and GH 11, 89 and 48%, respectively, of the CREs occurred within 3 h following greenhouse watering. When greenhouse temperatures exceeded 25°C for 21 days in May (GH 2) and 19 days in March (GH 11), atmospheric conidial concentrations were reduced 80 and 75% from the previous months, respectively.

scholarly journals Inoculation Method, Temperature, and Relative Humidity Affect Leaf and Neck Anthracnose, a New Onion Disease in Michigan

2018 ◽  
Vol 19 (1) ◽  
pp. 64-68
Author(s):  
Lina M. Rodriguez-Salamanca ◽  
Rachel P. Naegele ◽  
Lina M. Quesada-Ocampo ◽  
Mary K. Hausbeck
Keyword(s):  
Relative Humidity ◽  
Disease Severity ◽  
Colletotrichum Coccodes ◽  
Conidial Suspension ◽  
New Disease ◽  
Inoculation Method ◽  
Millet Seed ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies

Leaf and neck anthracnose caused by Colletotrichum coccodes is a new disease of onion in Michigan. To test the effect of inoculation method, Prince onion seedlings were grown in the greenhouse and inoculated with either a conidial suspension of C. coccodes (alone or with an abrasive agent) or infested millet seed (dry or wet, 2 or 5 g). Foliar disease severity was greater when a conidial suspension (>39%) was used compared with infested millet seed (≤24.3%). Growth chamber studies were conducted using Infinity onion seedlings that were inoculated with a conidial suspension spray to determine the effects of temperature (15, 20, 25, or 30°C) and duration (0, 12, 24, 48, or 72 h) of high (95 ± 5%) relative humidity (RH) on disease severity (percentage of leaf area with C. coccodes lesions). Significant differences and interactions among temperature and RH were observed. The combination of high temperature (≥25°C) and extended (≥24 h) high RH resulted in >20% disease severity 28 days postinoculation. Results suggest that onion leaf and neck anthracnose symptoms are likely to be more severe when the environmental conditions are ≥25°C with ≥24 h of high RH.

Environmental Effects on MSMA Phytotoxicity to Wild-Type and Arsenical Herbicide-Resistant Common Cocklebur (Xanthium strumarium)

1996 ◽  
Vol 10 (4) ◽  
pp. 809-814 ◽  
Author(s):  
Chandrashekhar I. Nimbal ◽  
David R. Shaw ◽  
Gene D. Wills ◽  
Stephen O. Duke
Keyword(s):  
Relative Humidity ◽  
Xanthium Strumarium ◽  
Wild Type ◽  
Fresh Weight ◽  
Low Light ◽  
Herbicide Resistant ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Weed Resistance

Effects of temperature, relative humidity, and light on MSMA phytotoxicity to wild-type and arsenical herbicide-resistant biotypes of common cocklebur grown from seed collected in Mississippi were evaluated. In growth chamber studies, 20-d-old plants were sprayed with 0.5 kg ai/ha of MSMA, and after 7 d, fresh weight and chlorophyll content were measured to estimate phytotoxicity. All three environmental factors influenced the level of weed resistance. In studies with day/night temperatures of 30/25 C and 500 μmol/m2/s PPFD light with a 14-h photoperiod, phytotoxicity of MSMA at 40% relative humidity was minimal, but was significantly greater at 60 and 90% relative humidities. The resistant (R) biotype was affected less than the susceptible (S) biotype at the higher relative humidities. The level of resistance estimated by fresh weight reduction was greatest at 30/25 C, but was most pronounced at 35/30 C using chlorophyll measurements. Resistance was lowest at 25/20 C by either measurement. MSMA phytotoxicity occurred at light intensities of 75, 500, and 750 μmol/m2/s PPFD; however, biotypic response was greatest at 500, followed by 750 μmol/m2/s PPFD. Resistance of the (R) biotype to MSMA was not significant at 75 μmol/m2/s, suggesting that differentiation between the biotypes for MSMA sensitivity would be difficult under low light.

Mineral Nutrition and the Parasite-Host Relationship of Witchweed

Weed Science ◽  
1971 ◽  
Vol 19 (5) ◽  
pp. 528-533 ◽  
Author(s):  
G. H. Egley
Keyword(s):  
Relative Humidity ◽  
Mineral Nutrition ◽  
Mineral Nutrients ◽  
High Relative Humidity ◽  
Nutrient Level ◽  
Sorghum Vulgare ◽  
Nutrient Levels ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Relationship Of

The influence of mineral nutrition on the parasite-host relationship of witchweed (Striga luteaLour.) and sorghum (Sorghum vulgarePers. ‘Texas Bighead’) was investigated in greenhouse and growth chamber studies. Sorghum was grown in Eustis loamy sand, either infested or not infested with witchweed, and treated with one of three levels of mineral nutrients. Witchweed reduced host-shoot yields by about 70% at the low nutrient levels and by about 45% at the highest nutrient level. Witchweed produced seed at all nutrient levels, whereas the host produced seed at the highest level only. Increased nutrition also increased witchweed yields. Regardless of nutrient level, an early attack by witchweed was more destructive to the host than a late attack. Growth of witchweed in soil also was studied after the parasite was detached from the host or the host shoot was removed. When only the host shoot was removed, (a) witchweed growth was inhibited; (b) feeding of sucrose to witchweed did not restore parasite growth; (c) mineral nutrients were toxic to the parasite; and (d) high relative humidity around witchweed protected it from the nutrient toxicity. High relative humidity enhanced survival of the detached parasite but markedly inhibited growth of witchweed in the intact parasite-host relationship.

scholarly journals Effect of Wetness Duration and Temperature on the Development of Anthracnose on Selected Almond Tissues and Comparison of Cultivar Susceptibility

2011 ◽  
Vol 101 (8) ◽  
pp. 1013-1020 ◽  
Author(s):  
J. Diéguez-Uribeondo ◽  
H. Förster ◽  
J. E. Adaskaveg
Keyword(s):  
Analysis Of Covariance ◽  
Effect Of Temperature ◽  
Colletotrichum Acutatum ◽  
Disease Development ◽  
Common Slope ◽  
Significant Difference ◽  
Different Temperatures ◽  
Chamber Studies ◽  
Cultivar Susceptibility ◽  
Growth Chamber Studies

Blossoms, leaves, fruit, and woody tissues of almond can be affected by anthracnose caused by Colletotrichum acutatum. Because the disease occurs throughout rainy spring seasons, the effect of temperature and wetness duration on disease development was evaluated in controlled studies. The lowest inoculum concentration where disease developed on leaves was 104 conidia/ml. Longer wetness durations were needed for leaves than for blossoms and disease increased linearly with increasing wetness durations. Inoculation temperature mainly affected final disease levels. Temperature during incubation affected the rate of disease development, while final disease levels were very similar at 10, 15, or 20°C. An analysis of covariance was performed to compare regressions of the effects of wetness and temperature on disease development for several almond cultivars. For blossom inoculations at 15°C in growth-chamber studies, a common slope model was statistically sufficient to describe all four cultivars. Cultivar Nonpareil (NP) had a significantly (P < 0.05) lower adjusted means at the midpoint than cultivars Carmel (CA), NePlus Ultra (NU), and Wood Colony (WC). For blossom inoculations at 20°C and for leaf inoculations at all temperatures evaluated, an unequal slope model was statistically justified for comparing regression lines. For blossoms, the slopes were significantly different (P < 0.05) for pair-wise comparisons of CA-NU, NU-WC, and NP-WC. For leaves, most of the cultivars responded differently to infection at different temperatures. Two of the pair-wise comparisons demonstrated unequal slopes at all three temperatures evaluated (i.e., NU-NP and NU-WC). Overall, for blossoms and leaves, NP was the least susceptible, NU was the most susceptible, and WC and CA showed an intermediate susceptibility. In field blossom and fruit studies, a common slope model was statistically sufficient to describe all four cultivars. NP had a significantly lower midpoint (i.e., was less susceptible) than CA or WC, whereas no significant difference (P > 0.1) occurred in comparisons between CA and WC.

scholarly journals Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea Mays)

PLoS ONE ◽  
2012 ◽  
Vol 7 (3) ◽  
pp. e33741 ◽  
Author(s):  
Paul Szpak ◽  
Fred J. Longstaffe ◽  
Jean-François Millaire ◽  
Christine D. White
Keyword(s):  
Zea Mays ◽  
Stable Isotope ◽  
Growth Chamber ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Seabird Guano

Biocontrol of seed-borne Alternaria raphani and A. brassicicola

1987 ◽  
Vol 33 (10) ◽  
pp. 850-856 ◽  
Author(s):  
G. Vannacci ◽  
G. E. Harman
Keyword(s):  
Biological Control ◽  
Host Range ◽  
Trichoderma Harzianum ◽  
Pythium Species ◽  
Biological Control Agents ◽  
Fusarium Sp ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Radish Seedlings

Forty-two microorganisms were tested as biological control agents against Alternaria raphani and A. brassicicola. Tests were conducted for in vitro antagonistic ability, for ability to control the pathogens on naturally infected seeds germinated on moistened blotters, and in planting mix in growth chamber studies, and for their ability to reduce pod infection. The organisms tested were obtained from cruciferous seeds or were strains already identified as being effective against soil-borne Pythium species. The blotter test indicated that six organisms increased both the number of healthy seedlings and the number of seedlings produced from A. raphani infected radish seeds. An additional seven strains improved either germination or increased the number of healthy seedlings. Twenty-nine organisms increased the number of healthy cabbage seedlings from A. brassicicola infected seeds, but total germination was not modified by any treatment. Experiments in planting mix showed that five antagonists (Chaetomium globosum, two strains of Trichoderma harzianum, T. koningii, and Fusarium sp.) increased the number of healthy plants in both radish samples tested, while four additional antagonists provided a significant increase in only one of the samples tested. The five antagonists that consistently increased numbers of healthy radish seedlings also decreased pod infection by A. raphani. None were as effective as iprodrone, however. Several effective antagonists were found to be mycoparasitic against Alternaria spp. Some strains of Trichoderma previously found to be effective against Pythium spp. were also effective against Alternaria spp., indicating that these strains have a wide host range.

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