Damage thresholds and population dynamics of Meloidogyne chitwoodi on carrot (Daucus carota) at different seed densities

Yield loss of carrot (Daucus carota) cv. Nerac caused by Meloidogyne chitwoodi and population dynamics of this nematode were studied using a range of 13 nematode densities at three seed densities (2, 4, 18 seeds pot−1) in a climate-controlled glasshouse. Yield and quality data were fitted to Seinhorst’s yield models. Final population densities were fitted to the population dynamic models for sedentary and free-living nematodes. The tolerance limits for yield loss were 0.34, 0.62 and 0.50, while that of quality were 0.012, 0.142 and 0.813 second-stage juveniles (J2) (g dry soil)−1 at increasing seed densities, respectively. The minimum yield (m), increased with seed density: 0.25, 0.30 and 0.50; the minimum quality yield was 0.10, 0.08 and 0.15 J2 (g dry soil)−1 at increasing seed densities, respectively. Both maximum multiplication rates and maximum population densities increased with increasing seed density but were generally low. Carrot cv. Nerac can be considered a bad host for M. chitwoodi.

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Estimation of partial resistance in potato genotypes against Meloidogyne chitwoodi

Nematology ◽

10.1163/138855410x528497 ◽

2011 ◽

Vol 13 (4) ◽

pp. 477-489 ◽

Cited By ~ 11

Author(s):

Thomas Been ◽

Corrie Schomaker ◽

Patrick Norshie

Keyword(s):

Partial Resistance ◽

Damage Threshold ◽

Internal Quality ◽

Yield Reduction ◽

Initial Population ◽

Multiplication Rate ◽

Population Densities ◽

Meloidogyne Chitwoodi ◽

Industrial Processing ◽

Final Population

AbstractThree new potato genotypes, designated AR 04-4107, AR 04-4096 and AR 04-4098, with resistance towards Meloidogyne chitwoodi, and the susceptible cv. Désirée were grown at a range of population densities of M. chitwoodi in a climate-controlled glasshouse in order to establish the presence and degree of partial resistance. Tuber parts of about 12 g were planted at densities (Pi) of 0, 0.5, 1, 2, 4, 8, 16, 32, 64, 128 and 256 second-stage juveniles (J2) (g dry soil)−1. The plants were allowed to grow for a period of 105 days. Tomato cv. Moneymaker was included and inoculated at Pi = 2 J2 (g soil)−1 to verify the quality of the inoculum by measuring the multiplication rate. Plant height was measured weekly over 11 weeks. At harvest, fresh shoot, root and tuber weights, and number of tubers were measured to express yield. Final population densities (Pf) were calculated as the total number of nematodes found in soil and roots. Tubers were scored for visible symptoms and a root-knot index was calculated. The relation between pre-plant population densities (Pi) and nematode densities at harvest (Pf) was fitted using R. The multiplication rate a of M. chitwoodi on AR 04-4107, AR 04-4096, AR 04-4098 and cv. Désirée was 0.55, 0.27, 0.91 and 32, respectively. Partial resistance rsa of AR 04-4107, AR 04-4096 and AR 04-4098 was 1.7%, 0.8% and 2.8%, respectively. Partial resistance expressed as rsM was 0.2%, 0.2% and 0.1%, respectively. It can be concluded that AR 04-4107, AR 04-4096 and AR 04-4098 are strongly partially resistant to M. chitwoodi. Also, the population dynamics curves run almost parallel between both the tested genotypes and the reference cultivar, indicating that a simple and cheap partial resistance test is feasible. When tuber yields were fitted to the Seinhorst model for yield reduction, cv. Désirée showed a minimum yield (m) of 0.86, while all three resistant genotypes suffered no yields losses at all (m = 1), which indicates that the observed resistance was associated with tolerance. As a result of the remarkably high partial resistance, quality damage was low compared with cv. Désirée. The root-knot index, which takes into account internal quality damage of the potato tuber, was below 10 for all genotypes with partial resistance, the lower damage threshold used for industrial processing of consumption potatoes. Visible symptoms on the tuber skin were absent up to densities of 32 J2 (g soil)−1 for genotypes AR 04-4098 and AR 04-4096 and 2 J2 (g soil)−1 for AR 04-4107, and significantly reduced at higher densities when compared with the susceptible cv. Désirée. However, when tuber peels were investigated, egg masses were detected in tubers at almost all initial population densities.

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A routine test for the relative susceptibility of potato genotypes with resistance to Meloidogyne chitwoodi

Nematology ◽

10.1163/15685411-00003016 ◽

2016 ◽

Vol 18 (9) ◽

pp. 1079-1094 ◽

Cited By ~ 3

Author(s):

Misghina G. Teklu ◽

Corrie H. Schomaker ◽

Thomas H. Been ◽

Leendert P.G. Molendijk

Keyword(s):

Logistic Model ◽

Multiplication Rate ◽

Experimental Conditions ◽

Meloidogyne Chitwoodi ◽

Second Stage ◽

Final Population ◽

Pot Size ◽

Optimal Protocol ◽

Dry Soil ◽

Resistant Genotypes

The population dynamics of Meloidogyne chitwoodi on eight potato genotypes was compared to the susceptible cv. Desiree in four glasshouse experiments. The initial nematode densities consisted of log series 2x, with . Seinhorst’s logistic model was fitted to the final population densities to estimate the parameters maximum multiplication rate (a), maximum population density (M) and the ratios RSa, RSM and . Average RSa and RSM of the seven resistant genotypes were smaller than 0.29%. The ratios on six resistant genotypes and cv. Desiree were the same, 1.3, indicating independence of RS. One genotype stood out with , whereby RSa < RSM. Both RS and were unaffected by pot size or experimental conditions. Screening protocols at second-stage juveniles (g dry soil)−1 in 2 or 3 kg pots were evaluated for distinctiveness between the two genotype groups. Based on the results, an optimal protocol for a routine resistance test is proposed.

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Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

Canadian Journal of Botany ◽

10.1139/b92-249 ◽

1992 ◽

Vol 70 (10) ◽

pp. 2005-2008 ◽

Cited By ~ 17

Author(s):

Robert Hall ◽

Lana Gay Phillips

Keyword(s):

Population Dynamics ◽

Phaseolus Vulgaris ◽

Population Density ◽

Fusarium Solani ◽

Population Densities ◽

Total Rainfall ◽

Colony Forming Units ◽

Bean Crop ◽

Previous Summer ◽

Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

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Interannual variation in the epibenthic megafauna at the shallowest station of the HAUSGARTEN observatory (79° N, 6° E)

Biogeosciences Discussions ◽

10.5194/bgd-9-18039-2012 ◽

2012 ◽

Vol 9 (12) ◽

pp. 18039-18081 ◽

Cited By ~ 1

Author(s):

K. S. Meyer ◽

M. Bergmann ◽

T. Soltwedel

Keyword(s):

Population Dynamics ◽

Deep Sea ◽

Interannual Variation ◽

Suspension Feeding ◽

Fram Strait ◽

Population Densities ◽

Camera System ◽

Sea Floor ◽

Time Period ◽

Food Input

Abstract. Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007 and 2012 at the shallowest station (HG I, ~ 1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The varying dynamics of different species may have been caused by differential capacities of populations to respond to increased food input through either recruitment or migration.

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Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

Marine and Freshwater Research ◽

10.1071/mf9770417 ◽

1977 ◽

Vol 28 (4) ◽

pp. 417 ◽

Cited By ~ 19

Author(s):

R Marchant ◽

WD Williams

Keyword(s):

Population Dynamics ◽

Population Density ◽

Temperature Stress ◽

Brine Shrimp ◽

Dry Weight ◽

Salt Lakes ◽

Confidence Limits ◽

Length Frequency ◽

Population Densities ◽

The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

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Viability-PCR Allows Monitoring Yeast Population Dynamics in Mixed Fermentations Including Viable but Non-Culturable Yeasts

Foods ◽

10.3390/foods9101373 ◽

2020 ◽

Vol 9 (10) ◽

pp. 1373

Author(s):

Yurena Navarro ◽

María-Jesús Torija ◽

Albert Mas ◽

Gemma Beltran

Keyword(s):

Population Dynamics ◽

Alcoholic Fermentation ◽

Yeast Species ◽

Culture Media ◽

Microbial Interactions ◽

Fast Method ◽

Yeast Population ◽

Final Population ◽

Differential Medium ◽

Yeast Interactions

The use of controlled mixed inocula of Saccharomyces cerevisiae and non-Saccharomyces yeasts is a common practice in winemaking, with Torulaspora delbrueckii, Lachancea thermotolerans and Metschnikowia pulcherrima being the most commonly used non-Saccharomyces species. Although S. cerevisiae is usually the dominant yeast at the end of mixed fermentations, some non-Saccharomyces species are also able to reach the late stages; such species may not grow in culture media, which is a status known as viable but non-culturable (VBNC). Thus, an accurate methodology to properly monitor viable yeast population dynamics during alcoholic fermentation is required to understand microbial interactions and the contribution of each species to the final product. Quantitative PCR (qPCR) has been found to be a good and sensitive method for determining the identity of the cell population, but it cannot distinguish the DNA from living and dead cells, which can overestimate the final population results. To address this shortcoming, viability dyes can be used to avoid the amplification and, therefore, the quantification of DNA from non-viable cells. In this study, we validated the use of PMAxx dye (an optimized version of propidium monoazide (PMA) dye) coupled with qPCR (PMAxx-qPCR), as a tool to monitor the viable population dynamics of the most common yeast species used in wine mixed fermentations (S. cerevisiae, T. delbrueckii, L. thermotolerans and M. pulcherrima), comparing the results with non-dyed qPCR and colony counting on differential medium. Our results showed that the PMAxx-qPCR assay used in this study is a reliable, specific and fast method for quantifying these four yeast species during the alcoholic fermentation process, being able to distinguish between living and dead yeast populations. Moreover, the entry into VBNC status was observed for the first time in L. thermotolerans and S. cerevisiae during alcoholic fermentation. Further studies are needed to unravel which compounds trigger this VBNC state during alcoholic fermentation in these species, which would help to better understand yeast interactions.

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Interannual variation in the epibenthic megafauna at the shallowest station of the HAUSGARTEN observatory (79° N, 6° E)

Biogeosciences ◽

10.5194/bg-10-3479-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 3479-3492 ◽

Cited By ~ 20

Author(s):

K. S. Meyer ◽

M. Bergmann ◽

T. Soltwedel

Keyword(s):

Population Dynamics ◽

Deep Sea ◽

Interannual Variation ◽

Suspension Feeding ◽

Fram Strait ◽

Population Densities ◽

Camera System ◽

Sea Floor ◽

Time Period ◽

Food Input

Abstract. Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007, and 2012 at the shallowest station (HG I, ∼1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The community of HG I may be unique in its response to elevated food input, which resulted in higher evenness and diversity in 2012.

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Comment on “Soybean Aphid Population Dynamics, Soybean Yield Loss, and Development of Stage-Specific Economic Injury Levels” by M. A. Catangui, E. A. Beckendorf, and W. E. Riedell, Agron. J. 101:1080-1092 (2009)

Agronomy Journal ◽

10.2134/agronj2009.8888l ◽

2010 ◽

Vol 102 (1) ◽

pp. 55-59 ◽

Cited By ~ 2

Author(s):

Matt O'Neal ◽

Kevin Johnson ◽

Erin Hodgson ◽

Dave Ragsdale ◽

Ian MacRae ◽

...

Keyword(s):

Population Dynamics ◽

Yield Loss ◽

Soybean Aphid ◽

Aphid Population ◽

Soybean Yield ◽

Economic Injury

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Tuber and root resistance of potato genotypes against Meloidogyne chitwoodi in the presence of Avena strigosa, related to tuber quality

Nematology ◽

10.1163/15685411-00003047 ◽

2017 ◽

Vol 19 (3) ◽

pp. 281-291 ◽

Cited By ~ 1

Author(s):

Misghina G. Teklu ◽

Corrie H. Schomaker ◽

Thomas H. Been ◽

Leendert P.G. Molendijk

Keyword(s):

Tuber Quality ◽

Initial Population ◽

Hatching Rate ◽

Root Weight ◽

Meloidogyne Chitwoodi ◽

Tuber Resistance ◽

Avena Strigosa ◽

Final Population ◽

Root Resistance

Relative tuber infestation and quality of two Meloidogyne chitwoodi resistant potato genotypes, AR04-4096 and 2011M1, were compared in glasshouse experiments at initial population density () = 16 second-stage juveniles (g dry soil)−1 in the presence and absence of the bristle oat, Avena strigosa. When A. strigosa was added, ( final population) on both AR04-4096 and 2011M1 increased 130×, increased 1.9 and 3.7×, respectively, while × fresh root weight (FRW)−1 was the same. Nematode hatch from peel of AR04-4096, without A. strigosa, was delayed by 3 weeks but relative hatching rate was increased. Although the RStuber (RS = Relative Susceptibility) of both AR04-4096 and 2011M1 were lower than 1%, in the presence of A. strigosa tuber quality of 2011M1 dropped below the marketable level, while that of AR04-4096 was hardly affected. We conclude that: i) is influenced by root mass; ii) root quality influences nematode hatch; iii) tuber quality is not an estimator for tuber resistance, and the reverse; iv) root resistance is equal to tuber resistance.

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