EFFECTS OF CULTIVAR RESISTANCE, LEAF WETNESS DURATION AND TEMPERATURE ON RATE OF DEVELOPMENT OF POTATO EARLY BLIGHT

1985 ◽  
Vol 65 (1) ◽  
pp. 179-184 ◽  
Author(s):  
J. D. HOLLEY ◽  
R. HALL ◽  
G. HOFSTRA
Keyword(s):  
Infection Rate ◽  
Early Blight ◽  
Alternaria Solani ◽  
Field Conditions ◽  
Leaf Wetness ◽  
Regression Equations ◽  
Cultivar Resistance ◽  
Leaf Wetness Duration ◽  
Apparent Infection Rate ◽  
Highly Correlated

Regression models were developed from field observations over three seasons in Ontario, to relate apparent infection rate (Y) of early blight, caused by Alternaria solani Sorauer, on three potato cultivars, Kennebec, Chieftain, and Norchip, to leaf wetness duration (W) and air temperature (T). Among regression equations of the form Y = a + bW + cT + dWT or Y = a + bW, cultivar-specific equations accounted for more variability in Y than equations derived from all cultivars. In all-cultivar equations and cultivar-specific equations, W accounted for 85%–89% of the variability in Y. Therefore, cultivar resistance and the average daily duration of leaf wetness were identified as important factors determining apparent infection rate under field conditions. Temperature, either singly or in combination with leaf wetness, accounted for less than 10% of the variability in Y and was negatively correlated with Y and W. The product of temperature and wetness was highly correlated with Y but, under field conditions, an increase in temperature tended to decrease the duration of leaf wetness, and therefore the value of Y as well. It is suggested that cultivar resistance and duration of leaf wetness will be important factors to be considered in the prediction of apparent infection rate and in the development of a practical weather-timed spray program for early blight of potato.Key words: Alternaria solani, Solanum tuberosum, disease control, weather-timed spray

scholarly journals Bremia lactucae Infection Efficiency in Lettuce is Modulated by Temperature and Leaf Wetness Duration Under Quebec Field Conditions

Plant Disease ◽  
2015 ◽  
Vol 99 (7) ◽  
pp. 1010-1019 ◽  
Author(s):  
M. L. Fall ◽  
H. Van der Heyden ◽  
C. Beaulieu ◽  
O. Carisse
Keyword(s):  
Downy Mildew ◽  
Field Experiments ◽  
Field Conditions ◽  
Risk Indicators ◽  
Growth Chamber ◽  
Leaf Wetness ◽  
Risk Indicator ◽  
Bremia Lactucae ◽  
Infection Efficiency ◽  
Leaf Wetness Duration

More than 80% of Canadian lettuce production is located in the province of Quebec. Yet most of our knowledge on the epidemiology of lettuce downy mildew (Bremia lactucae) is derived from controlled-condition experiments or field experiments conducted in subtropical climates and, thus, cannot readily be applied to Quebec lettuce production. The influence of temperature and leaf wetness duration on the infection efficiency (IE) of B. lactucae was studied for 4 years (2003, 2004, 2012, and 2013) under field and growth-chamber conditions. IE was defined as the ratio of the number of lesions/leaf to the airborne conidia concentration (ACC). B. lactucae ACC was measured with rotating-arm samplers three times/week. In addition, 72 lettuce trap plants/sampling day were exposed to the potential airborne B. lactucae inoculum and disease intensity was assessed after 7 days of incubation in greenhouse. Under growth-chamber conditions, an ACC of 1 conidium/m3 was sufficient to cause 1 lesion/leaf, and IE ranged from 0.25 to 1.00. Under field conditions, an ACC of 10 to 14 conidia/m3 was required to cause 1 lesion/leaf, and IE ranged from 0.02 to 0.10, except in 2004, when IE ranged from 0.03 to 1.00. IE increased with increasing leaf wetness duration but decreased with increasing temperature. Also, considering an observed average temperature range from 10 to 20°C in the area of Quebec, 2 h of leaf wetness was sufficient for infection by B. lactucae. Therefore, under Quebec lettuce production conditions, a leaf wetness period of 2 h and an ACC of 10 to 14 conidia/m3 can be used as risk indicators to facilitate disease management decisions. Also, under typical Quebec weather conditions, measuring both morning and evening leaf wetness events could be used to improve the reliability of leaf wetness duration as a downy mildew risk indicator. Further research is needed to validate these risk indicators for integration into management strategies.

scholarly journals Assessment of fungicides against early blight of tomato induced by Alternaria solani (Ellis & Martin) under field conditions

2020 ◽  
Vol 8 (6) ◽  
pp. 693-696
Author(s):  
OP Sharma ◽  
Sahil Pruthi ◽  
Geeta Mohan ◽  
Manjeet Kaur ◽  
Manju Kumari
Keyword(s):  
Early Blight ◽  
Alternaria Solani ◽  
Field Conditions

scholarly journals Evaluation of field pea germplasm against rust disease caused by Uromyces viciae fabae De Bary in glass house and field conditions

2018 ◽  
Vol 44 (3) ◽  
pp. 443-449 ◽  
Author(s):  
Deepak Singh ◽  
Ashish Kumar Gupta ◽  
Anil Kumar Singh ◽  
Ajoy Kumar Singh ◽  
Santosh Kumar
Keyword(s):  
Leaf Area ◽  
Infection Rate ◽  
Field Condition ◽  
Field Pea ◽  
Field Conditions ◽  
Breeding Programme ◽  
Rust Disease ◽  
Apparent Infection Rate ◽  
Moderate Resistance

Seventy three germplasm of field pea were tested under glasshouse and field condition against rust disease caused by Uromyces viciae fabae (Pers.) de Bary. Among screened germplasms, 30 susceptible, 40 highly susceptible and 3 belonged to moderately resistance group. The susceptible germplasm showed leaf area with symptoms (LAS) ranged from 30 to 65% with area under disease progressive curve (AUDPC) values from 77.5 to 1290 and apparent infection rate from 0.0134 to 0.1698 and highly susceptible germplasm showed LAS ranged from 60 to 95% with AUDPC values ranged from 1075 to 2179. Apparent infection rate ranged from 0.0616 to 0.6950 while moderately resistance germplasm showed LAS ranged from 20 to 24% with AUDPC values ranged from 350 to 438 and apparent infection rate ranged from 0.1180 to 0.1198 in field as well as glasshouse conditions. The moderate resistance germplasm JPF 99025, KPMR 615 and KPMR 551showed lowest LAS, AUDPC value and apparent infection rate, hence, these germplasms could be used in breeding programme.

Predicting in Vivo Soft Tissue Masses of the Lower Extremity Using Segment Anthropometric Measures and DXA

2005 ◽  
Vol 21 (4) ◽  
pp. 371-382 ◽  
Author(s):  
Jeffrey D. Holmes ◽  
David M. Andrews ◽  
Jennifer L. Durkin ◽  
James J. Dowling
Keyword(s):  
Soft Tissue ◽  
Lower Extremity ◽  
Prediction Equation ◽  
Regression Equations ◽  
Anthropometric Measures ◽  
Soft Tissue Masses ◽  
Highly Correlated ◽  
Relative Errors ◽  
Dxa Scans

The purpose of this study was to derive and validate regression equations for the prediction of fat mass (FM), lean mass (LM), wobbling mass (WM), and bone mineral content (BMC) of the thigh, leg, and leg + foot segments of living people from easily measured segmental anthropometric measures. The segment masses of 68 university-age participants (26 M, 42 F) were obtained from full-body dual photon x-ray absorptiometry (DXA) scans, and were used as the criterion values against which predicted masses were compared. Comprehensive anthropometric measures (6 lengths, 6 circumferences, 8 breadths, 4 skinfolds) were taken bilaterally for the thigh and leg for each person. Stepwise multiple linear regression was used to derive a prediction equation for each mass type and segment. Prediction equations exhibited high adjustedR2values in general (0.673 to 0.925), with higher correlations evident for the LM and WM equations than for FM and BMC. Predicted (equations) and measured (DXA) segment LM and WM were also found to be highly correlated (R2= 0.85 to 0.96), and FM and BMC to a lesser extent (R2= 0.49 to 0.78). Relative errors between predicted and measured masses ranged between 0.7% and –11.3% for all those in the validation sample (n= 16). These results on university-age men and women are encouraging and suggest that in vivo estimates of the soft tissue masses of the lower extremity can be made fairly accurately from simple segmental anthropometric measures.

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