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An Agent-Based Metapopulation Model Simulating Virus-Based Biocontrol of Heterodera Glycines Cover

An Agent-Based Metapopulation Model Simulating Virus-Based Biocontrol of Heterodera Glycines

Journal of Nematology
Volume 50 (2018): Issue 2 (January 2018)
By: Safyre Anderson,  Chinmay Soman,  Sadia Bekal,  Leslie Domier,  Kris Lambert and  Kaustubh Bhalerao  
Open Access
|Jun 2018

Figures & Tables

Figure 1:

The Soybean Cyst Nematode Simulation (SCNSim) framework. Envi-ronment, Nematode, Viral Infection and Soybean boxes represent classes in an object-oriented framework, with their respective properties listed within the boxes, and interactions between each other shown by solid arrows. The Nematode class is a simplified model of the life cycle of the nematode Heterodera glycines. SCNSim stochastically simulates a population of nematode agents governed by a dynamic environment, health of the host soybean crops, and the nature of the viral infec- tion. Nematode transition between life stages. Stages J2-J4 feed on the soybean plant diminishing the plant health. The environment modulates the growth of the soybean plant as well as the hatching and transition to the cyst stage in the nematode. The viral parameters are a property of the nematode objects that reduce their health. Viruses transmit horizontally and vertically. Nematodes are removed from simulation when their Health parameter drops below zero.
The Soybean Cyst Nematode Simulation (SCNSim) framework. Envi-ronment, Nematode, Viral Infection and Soybean boxes represent classes in an object-oriented framework, with their respective properties listed within the boxes, and interactions between each other shown by solid arrows. The Nematode class is a simplified model of the life cycle of the nematode Heterodera glycines. SCNSim stochastically simulates a population of nematode agents governed by a dynamic environment, health of the host soybean crops, and the nature of the viral infec- tion. Nematode transition between life stages. Stages J2-J4 feed on the soybean plant diminishing the plant health. The environment modulates the growth of the soybean plant as well as the hatching and transition to the cyst stage in the nematode. The viral parameters are a property of the nematode objects that reduce their health. Viruses transmit horizontally and vertically. Nematodes are removed from simulation when their Health parameter drops below zero.

Figure 2:

Soybean cyst nematode mortality across viral pathotypes. Each panel describes the mortality in the nematode population as a function of the mutation rate for a given initial virulence V0. Greater prevalence of the infection resulted in higher mortalities than the low release treatments.
Soybean cyst nematode mortality across viral pathotypes. Each panel describes the mortality in the nematode population as a function of the mutation rate for a given initial virulence V0. Greater prevalence of the infection resulted in higher mortalities than the low release treatments.

Figure 3:

SCN suppression over time at mutation rate of 0.4 across initial virulence V 0: (A) virus mortality rate changes over time; (B) virus prevalence changes over time; and (C) virus transmission rate changes over time for different virus initial virulence (V 0) rate.
SCN suppression over time at mutation rate of 0.4 across initial virulence V 0: (A) virus mortality rate changes over time; (B) virus prevalence changes over time; and (C) virus transmission rate changes over time for different virus initial virulence (V 0) rate.

Figure 4:

Replication ratio (R v) with respect to mutation rate of viruses with respect to mutation rate at five different initial virulence rate (V 0) over 4 crop years. Median R v values are accompanied by smoothing (loess) curves with 95% confidence bands.
Replication ratio (R v) with respect to mutation rate of viruses with respect to mutation rate at five different initial virulence rate (V 0) over 4 crop years. Median R v values are accompanied by smoothing (loess) curves with 95% confidence bands.

Figure 5:

Four-dimensional scatter plot showing virus-caused nematode mortali- ties over time across treatments by mutation rates and virulences. Each panel in the grid layout denotes the evolution of transmissibility b and virulence v over time for a specific mutation rate and initial virulence.
Four-dimensional scatter plot showing virus-caused nematode mortali- ties over time across treatments by mutation rates and virulences. Each panel in the grid layout denotes the evolution of transmissibility b and virulence v over time for a specific mutation rate and initial virulence.

Figure 6:

Relationship between transmissibility and virulence across three distinct initial virulence values (V 0 = 1.5, 2.0, and 2), with a single mutation rate, m = 0.4 over 4 years. Mortality rate of soybean cyst nematodes are shown in different colors.
Relationship between transmissibility and virulence across three distinct initial virulence values (V 0 = 1.5, 2.0, and 2), with a single mutation rate, m = 0.4 over 4 years. Mortality rate of soybean cyst nematodes are shown in different colors.

Numerical properties of the viruses in the Soybean Cyst Nematode Simulation Framework SCNSim_

Definition
PropertySymbolRangein vivoin silico
Viral Load L 0 1Amount of viral particles per hostScalar multiplier to nematode health decrement
Virulence V 0, v R > 0Pathogen damage inflicted on hostMultiplier to Viral Load
Transmissibility b 0, b 0 1Rate of infection of suscep-tible populationProportion of viral load sexu-ally transmitted from infected male to a recipient female or from female to egg
Prevalence i 0, i 0 1Disease prevalence in a populationFraction of initial population infected
Durability D 0 1Longevity of virus parti-cles.The complement is an ampli-fying constant on increasing viral load.
Mutation Rate M 0 1Proportion of progeny gen-eration with significant ge-netic variationProbability of virus proper-ties undergoing mutation

Environmental set points and nematode stages modeled in the Soybean Cyst Nematode Simulation Framework (SCNSim) based on figures in Schmitt et al_ (2004)_

Model compartmentParameter descriptionValue
SCN life cycle lawsSCN eggs per cyst300-500a
Minimum hatching temperature16° C
Maximum hatching temperature36° C
Cyst dormancy initialize temperature< 20° C
Probability of hatching from egg sac0.2b
Probability of hatching from cyst0.002b
SCN life stagesEgg state1-5 d
J1 state1-2 d
Unhatched J21-3000 d
Hatched J21-4 d
J33-4 d
J4 male5-6 d
J4 female3-4 d
Adult male1-21 d
Adult female2-60 d
Range of mating1-21 d
Gestation period3-5 d
Egg Sac1-3000 d
Cyst1-3000 d
Soybean growthMinimum germinate temperature13 ° C
Soybean germinate date115 days (about April 25)
Soybean harvest date240 days (about August 28)
Optimal soybean growth temperature27° C
SCN ParasitismMinimum soybean age for parasitism20 days post germinationc
Maximum soybean age for parasitism100 days post germinationc
Feed rate5%

Simulation parameters used in producing data on the Soybean Cyst Nematode Simulation SCNSim framework_

Simulation configurationSampling frequency4 days
Iterations10
Simulation duration5 years
Virus propertiesMutation rates (m)0, 0.1, 0.2, 0.4, 0.6, 0.8
Virulence (V 0)0.1, 0.5, 1, 1.5, 2, 2.5, 4
Transmissibility (b 0)0.5
Infection rate (i 0)0.2, 0.8
Durability (D)0.5
Viral load (L)0.5
DOI: https://doi.org/10.21307/jofnem-2018-002 | Journal eISSN: 2640-396X | Journal ISSN: 0022-300X
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Language: English
Page range: 79 - 90
Published on: Jun 3, 2018
Published by: Society of Nematologists, Inc.
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year
Keywords:
Biological control,
host-parasitic relationship,
numerical model,
soybean cyst nematode,
virulence evolution
Related subjects:
Life sciences,
Life sciences, other

© 2018 Safyre Anderson, Chinmay Soman, Sadia Bekal, Leslie Domier, Kris Lambert, Kaustubh Bhalerao, published by Society of Nematologists, Inc.
This work is licensed under the Creative Commons Attribution 4.0 License.

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