Intra- and interplot variability of Heterodera glycines population densities in experimental settings to soybean variety evaluations in Nebraska

Oscar Pérez-Hernández, Loren J. Giesler

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1 Citation (Scopus)

Abstract

The intra- and interplot variability of soybean cyst nematode (SCN; Heterodera glycines) population densities was characterized in three experimental areas in Nebraska in 2014. Through single-core cluster sampling of 4-m-long plots, a random pattern of SCN incidence (number of SCN-positive soil cores out of 10 per plot) within plots was suggested by the binomial distribution in one location. The detected randomness, however, was associated to the high SCN infestation level and tillage in the experimental area. In the other two experimental areas, the beta-binomial distribution adequately described SCN incidence (index of aggregation θ > 0; index of dispersion D > 1.0), suggesting the presence of an aggregated pattern within plots. Based on the properties of the fitted distributions, the intraplot aggregation of incidence affects the probability of cyst recovery during sampling and thereby the estimation of SCN population densities. At the interplot scale, correlogram analysis of 36 transects of 28 and 35 m showed that discrete foci of SCN population densities were spatially dependent with foci located up to 15 m away. This was confirmed by spatial autocorrelation, which indicated that SCN population densities in the 4-m-long plots were positively correlated with population densities of up to two contiguous plots. Interplot aggregation of SCN population densities suggests lack of independence among plots or experimental units. Altogether, the results of this study recommend that researchers conducting field experiments with H. glycines consider SCN spatial pattern, particularly, if rigorous comparisons among soybean varieties are sought. Consideration may comprise both the diagnostics of spatial dependence of SCN population densities in a prospective variety evaluation site, prior to spring sampling, and the subsequent allocation of varieties to plots based on their degree of spatial correlation. While limited to a single-year assessment, the information on SCN spatial pattern from the present study, coupled with that on soybean plant populations, row spacing, and soil conditions, can be useful to determine site suitability for a variety trial. The information could also be incorporated into statistical analysis to determine the number of replications needed to detect differences among varieties for their response to SCN.

Original languageEnglish (US)
Pages (from-to)123-136
Number of pages14
JournalCrop Protection
Volume94
DOIs
StatePublished - Apr 1 2017

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Heterodera glycines
population density
soybeans
incidence
variety trials
row spacing
autocorrelation
sampling
soil quality
tillage
statistical analysis
researchers

Keywords

  • Beta-binomial
  • Correlogram
  • Cyst nematode
  • Epidemiology
  • Soybean variety evaluations
  • Spatial pattern
  • Spatial variability

ASJC Scopus subject areas

  • Agronomy and Crop Science

Cite this

@article{1786c657fbfe4e1990e2bd13e5c61cb2,
title = "Intra- and interplot variability of Heterodera glycines population densities in experimental settings to soybean variety evaluations in Nebraska",
abstract = "The intra- and interplot variability of soybean cyst nematode (SCN; Heterodera glycines) population densities was characterized in three experimental areas in Nebraska in 2014. Through single-core cluster sampling of 4-m-long plots, a random pattern of SCN incidence (number of SCN-positive soil cores out of 10 per plot) within plots was suggested by the binomial distribution in one location. The detected randomness, however, was associated to the high SCN infestation level and tillage in the experimental area. In the other two experimental areas, the beta-binomial distribution adequately described SCN incidence (index of aggregation θ > 0; index of dispersion D > 1.0), suggesting the presence of an aggregated pattern within plots. Based on the properties of the fitted distributions, the intraplot aggregation of incidence affects the probability of cyst recovery during sampling and thereby the estimation of SCN population densities. At the interplot scale, correlogram analysis of 36 transects of 28 and 35 m showed that discrete foci of SCN population densities were spatially dependent with foci located up to 15 m away. This was confirmed by spatial autocorrelation, which indicated that SCN population densities in the 4-m-long plots were positively correlated with population densities of up to two contiguous plots. Interplot aggregation of SCN population densities suggests lack of independence among plots or experimental units. Altogether, the results of this study recommend that researchers conducting field experiments with H. glycines consider SCN spatial pattern, particularly, if rigorous comparisons among soybean varieties are sought. Consideration may comprise both the diagnostics of spatial dependence of SCN population densities in a prospective variety evaluation site, prior to spring sampling, and the subsequent allocation of varieties to plots based on their degree of spatial correlation. While limited to a single-year assessment, the information on SCN spatial pattern from the present study, coupled with that on soybean plant populations, row spacing, and soil conditions, can be useful to determine site suitability for a variety trial. The information could also be incorporated into statistical analysis to determine the number of replications needed to detect differences among varieties for their response to SCN.",
keywords = "Beta-binomial, Correlogram, Cyst nematode, Epidemiology, Soybean variety evaluations, Spatial pattern, Spatial variability",
author = "Oscar P{\'e}rez-Hern{\'a}ndez and Giesler, {Loren J.}",
year = "2017",
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day = "1",
doi = "10.1016/j.cropro.2016.12.014",
language = "English (US)",
volume = "94",
pages = "123--136",
journal = "Crop Protection",
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TY - JOUR

T1 - Intra- and interplot variability of Heterodera glycines population densities in experimental settings to soybean variety evaluations in Nebraska

AU - Pérez-Hernández, Oscar

AU - Giesler, Loren J.

PY - 2017/4/1

Y1 - 2017/4/1

N2 - The intra- and interplot variability of soybean cyst nematode (SCN; Heterodera glycines) population densities was characterized in three experimental areas in Nebraska in 2014. Through single-core cluster sampling of 4-m-long plots, a random pattern of SCN incidence (number of SCN-positive soil cores out of 10 per plot) within plots was suggested by the binomial distribution in one location. The detected randomness, however, was associated to the high SCN infestation level and tillage in the experimental area. In the other two experimental areas, the beta-binomial distribution adequately described SCN incidence (index of aggregation θ > 0; index of dispersion D > 1.0), suggesting the presence of an aggregated pattern within plots. Based on the properties of the fitted distributions, the intraplot aggregation of incidence affects the probability of cyst recovery during sampling and thereby the estimation of SCN population densities. At the interplot scale, correlogram analysis of 36 transects of 28 and 35 m showed that discrete foci of SCN population densities were spatially dependent with foci located up to 15 m away. This was confirmed by spatial autocorrelation, which indicated that SCN population densities in the 4-m-long plots were positively correlated with population densities of up to two contiguous plots. Interplot aggregation of SCN population densities suggests lack of independence among plots or experimental units. Altogether, the results of this study recommend that researchers conducting field experiments with H. glycines consider SCN spatial pattern, particularly, if rigorous comparisons among soybean varieties are sought. Consideration may comprise both the diagnostics of spatial dependence of SCN population densities in a prospective variety evaluation site, prior to spring sampling, and the subsequent allocation of varieties to plots based on their degree of spatial correlation. While limited to a single-year assessment, the information on SCN spatial pattern from the present study, coupled with that on soybean plant populations, row spacing, and soil conditions, can be useful to determine site suitability for a variety trial. The information could also be incorporated into statistical analysis to determine the number of replications needed to detect differences among varieties for their response to SCN.

AB - The intra- and interplot variability of soybean cyst nematode (SCN; Heterodera glycines) population densities was characterized in three experimental areas in Nebraska in 2014. Through single-core cluster sampling of 4-m-long plots, a random pattern of SCN incidence (number of SCN-positive soil cores out of 10 per plot) within plots was suggested by the binomial distribution in one location. The detected randomness, however, was associated to the high SCN infestation level and tillage in the experimental area. In the other two experimental areas, the beta-binomial distribution adequately described SCN incidence (index of aggregation θ > 0; index of dispersion D > 1.0), suggesting the presence of an aggregated pattern within plots. Based on the properties of the fitted distributions, the intraplot aggregation of incidence affects the probability of cyst recovery during sampling and thereby the estimation of SCN population densities. At the interplot scale, correlogram analysis of 36 transects of 28 and 35 m showed that discrete foci of SCN population densities were spatially dependent with foci located up to 15 m away. This was confirmed by spatial autocorrelation, which indicated that SCN population densities in the 4-m-long plots were positively correlated with population densities of up to two contiguous plots. Interplot aggregation of SCN population densities suggests lack of independence among plots or experimental units. Altogether, the results of this study recommend that researchers conducting field experiments with H. glycines consider SCN spatial pattern, particularly, if rigorous comparisons among soybean varieties are sought. Consideration may comprise both the diagnostics of spatial dependence of SCN population densities in a prospective variety evaluation site, prior to spring sampling, and the subsequent allocation of varieties to plots based on their degree of spatial correlation. While limited to a single-year assessment, the information on SCN spatial pattern from the present study, coupled with that on soybean plant populations, row spacing, and soil conditions, can be useful to determine site suitability for a variety trial. The information could also be incorporated into statistical analysis to determine the number of replications needed to detect differences among varieties for their response to SCN.

KW - Beta-binomial

KW - Correlogram

KW - Cyst nematode

KW - Epidemiology

KW - Soybean variety evaluations

KW - Spatial pattern

KW - Spatial variability

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