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Ashok Kumar Chanda - One of the best experts on this subject based on the ideXlab platform.
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effects of Inoculum Density and cultivar susceptibility on rhizoctonia damping off and crown and root rot in sugar beet
Plant Disease, 2021Co-Authors: Jason R Brantner, Ashok Kumar ChandaAbstract:Damping-off and crown and root rot of sugar beet caused by Rhizoctonia solani anastomosis group 2-2 (AG 2-2) are important soilborne diseases in Minnesota and North Dakota. Management involves an integrated approach, including crop rotation, use of resistant cultivars, and timely fungicide application. Our objectives were to evaluate the role of Inoculum Density and cultivar susceptibility on the onset and development of Rhizoctonia diseases and on yield and quality in sugar beet. Three cultivars varying in susceptibility were sown in field plots inoculated with 0, 20, 40, or 60 kg/ha of R. solani AG 2-2 IIIB infested barley during 2013 and 2015. In both years, there was a significant linear effect of Inoculum Density with decreasing area under the stand establishment curve (AUSEC), root yield, and sucrose quality as Inoculum Density increased. Cultivar susceptibility significantly affected AUSEC as well as sucrose quality in both years and root yield in 2013. In both years, there was an Inoculum Density by cultivar interaction on disease ratings, with the partially resistant cultivar resulting in lower ratings than the moderate and susceptible cultivars, especially as Inoculum Density increased. These results have implications for cultivar selection and for use and timing of postemergence fungicide application based on field history of Inoculum pressure.
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effects of Inoculum Density and cultivar susceptibility on rhizoctonia damping off and crown and root rot in sugar beet
Plant Disease, 2020Co-Authors: Jason R Brantner, Ashok Kumar ChandaAbstract:Damping-off and crown and root rot of sugar beet caused by Rhizoctonia solani AG 2-2 are important soilborne diseases in Minnesota and North Dakota. Management involves an integrated approach including crop rotation, use of resistant cultivars, and timely fungicide application. Our objectives were to evaluate the role of Inoculum Density and cultivar susceptibility on onset and development of Rhizoctonia diseases and on yield and quality in sugar beet. Three cultivars varying in susceptibility were sown in field plots inoculated with 0, 20, 40, or 60 kg ha-1 R. solani AG 2-2 IIIB infested barley during 2013 and 2015. In both years, there was a significant linear effect of Inoculum Density with decreasing area under the stand establishment curve (AUSEC), root yield, and sucrose quality as Inoculum Density increased. Cultivar susceptibility significantly affected AUSEC, and sucrose quality in both years and root yield in 2013. In both years, there was an Inoculum Density by cultivar interaction on disease ratings, with the partially resistant cultivar resulting in lower ratings than moderate and susceptible cultivars, especially as Inoculum Density increased. Results have implications for cultivar selection and use and timing of postemergence fungicide application based on field history of Inoculum pressure.
C R Wilson - One of the best experts on this subject based on the ideXlab platform.
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effect of Inoculum Density of sclerotium cepivorum on the ability of trichoderma koningii to suppress white rot of onion
Plant Disease, 2004Co-Authors: D A Metcalf, J.j.c. Dennis, C R WilsonAbstract:ABSTRACT Amendment of soil with Trichoderma koningii strain Tr5 grown on autoclaved white millet grain provided between 63 and 79% control of white rot of onion when added to soil containing 10, 25, 50, or 100 sclerotia of Sclerotium cepivorum per kilogram of soil at the time of onion seed sowing. There was no significant difference in the proportion of S. cepivorum infections suppressed among the different sclerotial Density treatments. Rhizosphere colonization by T. koningii Tr5 was assessed by incubating onion roots sampled from plants growing in soil with the appropriate Density of sclerotia, on a Trichoderma selective medium (Rose bengall-Allisan-streptomycin-Previcur agar) developed for the purpose of the study. Trichoderma spp. isolated were typed by comparison of culture morphology as well as polygalacturonase (PG) (EC 3.2.1.15) and pectinesterase (PE) (EC 3.1.1.11) isozyme profiles to the series of one PG and two PE isozymes known to be produced by T. koningii Tr5. The method was used successfull...
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effect of Inoculum Density of sclerotium cepivorum on the ability of trichoderma koningii to suppress white rot of onion
Plant Disease, 2004Co-Authors: D A Metcalf, J.j.c. Dennis, C R WilsonAbstract:Amendment of soil with Trichoderma koningii strain Tr5 grown on autoclaved white millet grain provided between 63 and 79% control of white rot of onion when added to soil containing 10, 25, 50, or 100 sclerotia of Sclerotium cepivorum per kilogram of soil at the time of onion seed sowing. There was no significant difference in the proportion of S. cepivorum infections suppressed among the different sclerotial Density treatments. Rhizosphere colonization by T. koningii Tr5 was assessed by incubating onion roots sampled from plants growing in soil with the appropriate Density of sclerotia, on a Trichoderma selective medium (Rose bengall-Allisan-streptomycin-Previcur agar) developed for the purpose of the study. Trichoderma spp. isolated were typed by comparison of culture morphology as well as polygalacturonase (PG) (EC 3.2.1.15) and pectinesterase (PE) (EC 3.1.1.11) isozyme profiles to the series of one PG and two PE isozymes known to be produced by T. koningii Tr5. The method was used successfully to assess rhizosphere colonization. Three rates of a millet grain formulation colonized by T. koningii Tr5 were added to soil (1,590, 3,180, and 4,770 kg/ha). At the lowest of these rates, 97% of roots were found to be colonized by isolates which could not be distinguished from T. koningii Tr5, whereas 8% of the roots from nontreated controls were colonized by such isolates. An objective of the study was to determine whether the ability of T. koningii Tr5 to suppress S. cepivorum infections was influenced by increased concentrations of both S. cepivorum sclerotia and T. koningii Tr5-colonized millet grain, and it was found that no further improvements in the percentage of disease suppression were recorded as a result of adding T. koningii Tr5-colonized millet to the soil at more than 1,590 kg/ha at any of the sclerotium concentrations tested.
Krishna V. Subbarao - One of the best experts on this subject based on the ideXlab platform.
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dynamics of lettuce drop incidence and sclerotinia minor Inoculum under varied crop rotations
Plant Disease, 2006Co-Authors: Jianjun Hao, Krishna V. SubbaraoAbstract:Field experiments were conducted to determine the population dynamics of Sclerotinia minor and incidence of lettuce drop at two sites during 1995 to 1998. Rotation treatments at the Spence site, which had a low Density of Inoculum ( 7 sclerotia per 100 cm3 of soil) that was distributed uniformly, included: continuous lettuce (LLLL), alternate crops of broccoli and lettuce (BLBL), continuous broccoli or lettuce (BBLL), and fallow-lettuce-fallow-lettuce (FLFL). Under continuous lettuce cropping (LLLL) at the Hartnell site, a progressively aggregated spatial pattern of Inoculum distribution developed, despite the initial uniform distribution of high Inoculum Density. In the fallow treatment (FLFL), the spatial pattern tended to be aggregated following a lettuce crop and less aggregated or random when left fallow. In contrast to these two treatments, treatments involving rotations with broccoli (BLBL and BBLL) exhibited consistently random spatial patterns of Inoculum regardless of the crop in the field. The marginal increases in the number of sclerotia contributed by the few diseased lettuce plants were offset by the significant reductions in the number of sclerotia by the broccoli residue. Spatial patterns of disease incidence reflected the pattern of Inoculum distribution in the soil at the Hartnell site. Higher Inoculum Density coupled with an aggregated distribution was associated with an aggregation in disease incidence. At Spence, this correlation was poor in most seasons because of progressive decline in the lettuce drop incidence and lack of treatment differences. In greenhouse experiments, the competence volume for S. minor sclerotia was quantified, which was calculated to be 25 3 for 100% infection and 200 cm3 for 50% infection. Thus, in 100 cm3 of soil, a minimum of four to five sclerotia are needed for 100% of infection, explaining the high correlation between Inoculum Density and disease incidence.
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effects of broccoli rotation on lettuce drop caused by sclerotinia minor and on the population Density of sclerotia in soil
Plant Disease, 2003Co-Authors: Jianjun Hao, Krishna V. Subbarao, S T KoikeAbstract:Field experiments were conducted at Spence Road site and at the Hartnell College East Campus site in Salinas, CA, to determine the effects of crop rotation with broccoli or a fallow period on lettuce drop caused by Sclerotinia minor and the Density of pathogen sclerotia in the soil. Treatments at the Spence Road site with low Inoculum Density ( 7 sclerotia per 100 cm3 of soil) distributed uniformly included: continuous lettuce (LLLL), broccoli-lettuce-broccoli-lettuce (BLBL), broccoli-broccoli-lettuce-lettuce (BBLL), and fallow-lettuce-fallow-lettuce (FLFL). At the Spence Road site, continuous lettuce did not increase lettuce drop incidence for at least 2 years, although an increase in soilborne sclerotia was observed annually but was below the threshold at which a correlation between Inoculum Density and disease incidence is observed. Rotation with broccoli resulted in small reductions in disease incidence only in the first year. The Density of sclerotia was lowest in the LFL treatment, and the highest in the LLL. At the Hartnell site, rotation with broccoli significantly reduced both sclerotia and lettuce drop incidence. The number of broccoli crops rather than the sequence of lettuce rotations with broccoli was critical for reducing the numbers of S. minor sclerotia in soil. Fallowing after a lettuce crop resulted in marginal reductions in sclerotia and lettuce drop incidence. Viability of recovered sclerotia was not significantly different between treatments, although differences between seasons were detected. Results suggest that rotations with broccoli can be a practical lettuce drop management strategy.
Jianjun Hao - One of the best experts on this subject based on the ideXlab platform.
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dynamics of lettuce drop incidence and sclerotinia minor Inoculum under varied crop rotations
Plant Disease, 2006Co-Authors: Jianjun Hao, Krishna V. SubbaraoAbstract:Field experiments were conducted to determine the population dynamics of Sclerotinia minor and incidence of lettuce drop at two sites during 1995 to 1998. Rotation treatments at the Spence site, which had a low Density of Inoculum ( 7 sclerotia per 100 cm3 of soil) that was distributed uniformly, included: continuous lettuce (LLLL), alternate crops of broccoli and lettuce (BLBL), continuous broccoli or lettuce (BBLL), and fallow-lettuce-fallow-lettuce (FLFL). Under continuous lettuce cropping (LLLL) at the Hartnell site, a progressively aggregated spatial pattern of Inoculum distribution developed, despite the initial uniform distribution of high Inoculum Density. In the fallow treatment (FLFL), the spatial pattern tended to be aggregated following a lettuce crop and less aggregated or random when left fallow. In contrast to these two treatments, treatments involving rotations with broccoli (BLBL and BBLL) exhibited consistently random spatial patterns of Inoculum regardless of the crop in the field. The marginal increases in the number of sclerotia contributed by the few diseased lettuce plants were offset by the significant reductions in the number of sclerotia by the broccoli residue. Spatial patterns of disease incidence reflected the pattern of Inoculum distribution in the soil at the Hartnell site. Higher Inoculum Density coupled with an aggregated distribution was associated with an aggregation in disease incidence. At Spence, this correlation was poor in most seasons because of progressive decline in the lettuce drop incidence and lack of treatment differences. In greenhouse experiments, the competence volume for S. minor sclerotia was quantified, which was calculated to be 25 3 for 100% infection and 200 cm3 for 50% infection. Thus, in 100 cm3 of soil, a minimum of four to five sclerotia are needed for 100% of infection, explaining the high correlation between Inoculum Density and disease incidence.
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effects of broccoli rotation on lettuce drop caused by sclerotinia minor and on the population Density of sclerotia in soil
Plant Disease, 2003Co-Authors: Jianjun Hao, Krishna V. Subbarao, S T KoikeAbstract:Field experiments were conducted at Spence Road site and at the Hartnell College East Campus site in Salinas, CA, to determine the effects of crop rotation with broccoli or a fallow period on lettuce drop caused by Sclerotinia minor and the Density of pathogen sclerotia in the soil. Treatments at the Spence Road site with low Inoculum Density ( 7 sclerotia per 100 cm3 of soil) distributed uniformly included: continuous lettuce (LLLL), broccoli-lettuce-broccoli-lettuce (BLBL), broccoli-broccoli-lettuce-lettuce (BBLL), and fallow-lettuce-fallow-lettuce (FLFL). At the Spence Road site, continuous lettuce did not increase lettuce drop incidence for at least 2 years, although an increase in soilborne sclerotia was observed annually but was below the threshold at which a correlation between Inoculum Density and disease incidence is observed. Rotation with broccoli resulted in small reductions in disease incidence only in the first year. The Density of sclerotia was lowest in the LFL treatment, and the highest in the LLL. At the Hartnell site, rotation with broccoli significantly reduced both sclerotia and lettuce drop incidence. The number of broccoli crops rather than the sequence of lettuce rotations with broccoli was critical for reducing the numbers of S. minor sclerotia in soil. Fallowing after a lettuce crop resulted in marginal reductions in sclerotia and lettuce drop incidence. Viability of recovered sclerotia was not significantly different between treatments, although differences between seasons were detected. Results suggest that rotations with broccoli can be a practical lettuce drop management strategy.
M A Blancolopez - One of the best experts on this subject based on the ideXlab platform.
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relationship between the Inoculum Density of verticillium dahliae and the progress of verticillium wilt of olive
Plant Disease, 2007Co-Authors: F J Lopezescudero, M A BlancolopezAbstract:ABSTRACT An experiment was conducted in microplots which were artificially infested with a defoliating isolate of Verticillium dahliae using seven different treatments of Inoculum densities ranging from 0 to 10 microsclerotia per gram of soil (ppg). The experiment was conducted in Andalucia (southern Spain), and the susceptible Spanish olive cv. Picual was used to determine the relationship between pathogen Inoculum Density and the progress of Verticillium wilt of olive (VWO). The Inoculum, produced on a sodium pectate cellophane medium, was found to efficiently infect olive trees. Symptoms first appeared 30 weeks after the trees were transplanted into infested soil. Periods of increasing disease incidence in the following seasons and years were mainly during spring and autumn, particularly in the second year after planting. Olive trees exhibited a high susceptibility to the defoliating pathotype of the pathogen, even at very low Inoculum levels; in fact, diseased plants were encountered throughout the ex...
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influence of Inoculum Density of defoliating and nondefoliating pathotypes of verticillium dahliae on epidemics of verticillium wilt of cotton in southern spain
Phytopathology, 1995Co-Authors: J Bejaranoalcazar, M A Blancolopez, J M Melerovara, Rafael M JimenezdiazAbstract:Linear regression analysis of data transformed according to several mathematical models showed no significant correlation between the Inoculum Density of Verticillium dahliae determined at sowing time in randomly chosen cotton fields and the incidence of plants with vascular discoloration, the incidence of plants with foliar symptoms, or a disease intensity index for Verticillium wilt of cotton calculated at the end of the crop season. Epidemic development of Verticillium wilt in cotton was investigated in field plots naturally infested with different Inoculum densities of the defoliating and nondefoliating pathotypes of V. dahliae in 1986 and 1987. The straight line model adequately described the increase in the incidence of plants showing foliar symptoms and the disease intensity index over the accumulated physiological time from sowing. For similar levels of initial Inoculum, the defoliating pathotype of V dahliae caused an earlier epidemic onset, a higher rate of increase in the incidence of foliar symptoms and the disease intensity index over physiological time, and a higher final amount of both disease measurements than the nondefoliating pathotype. Also, for the two disease measurements, the rate of progress increased with the initial Inoculum Density of the defoliating pathotype up to a threshold of 24 to 44 CFU/g of dry soil in 1986 and 44 to 75 CFU/g of dry soil in 1987. Differences in severity among Verticillium wilt epidemics were described more appropriately by the descriptive parameters of the increase in the disease intensity index over physiological time than by the corresponding parameters of the increase in the incidence of foliar symptoms.