Using Predictions Based on Geostatistics to Monitor Trends in Aspergillus flavus Strain Composition

Abstract

Aspergillus flavus is a soil-inhabiting fungus that frequently produces aflatoxins, potent carcinogens, in cottonseed and other seed crops. A. flavus S strain isolates, characterized on the basis of sclerotial morphology, are highly toxigenic. Spatial and temporal characteristics of the percentage of the A. flavus isolates that are S strain (S strain incidence) were used to predict patterns across areas of more than 30 km(2). Spatial autocorrelation in S strain incidence in Yuma County, AZ, was shown to extend beyond field boundaries to adjacent fields. Variograms revealed both short-range (2 to 6 km) and long-range (20 to 30 km) spatial structure in S strain incidence. S strain incidence at 36 locations sampled in July 1997 was predicted with a high correlation between expected and observed values (R = 0.85, P = 0.0001) by kriging data from July 1995 and July 1996. S strain incidence at locations sampled in October 1997 and March 1998 was markedly less than predicted by kriging data from the same months in prior years. Temporal analysis of four locations repeatedly sampled from April 1995 through July 1998 also indicated a major reduction in S strain incidence in the Texas Hill area after July 1997. Surface maps generated by kriging point data indicated a similarity in the spatial pattern of S strain incidence among all sampling dates despite temporal changes in the overall S strain incidence. Geostatistics provided useful descriptions of variability in S strain incidence over space and time.

Geostatistical analysis of the spatial distribution of mycotoxin concentration in bulk cereals

“…Effective and efficient sampling strategies can be designed through the characterization of the variogram parameters: the range, the sill and the nugget. Examples of studies where the variogram was used to analyse the spatial pattern of diseases are provided by Orum et al (1999) and Rekah et al (1999). The former used the variogram to determine the trends and distribution of the aflatoxigenic species Aspergillus flavus in soil.…”

Climate change impacts on mycotoxin risks in US maize

“…Several studies report that high soil temperature and drought stress are key environmental parameters that are positively correlated with aflatoxin contamination and increased incidence of aflatoxigenic strains or species (Horn and Dorner, 1999;Jaime-Garcia and Cotty, 2010;Orum et al, 1999). Although warmer temperatures and greater extremes in precipitation (especially drought) are known to shift the balance in favour of increased aflatoxin levels, the specific population genetic processes that drive this shift are unknown.…”

Monitoring Wheat Stripe Rust Using Remote Sensing Technologies in China

“…It is very useful for the studies on epidemic dynamics of plant disease during many years and more precise management of plant disease. The integration of RS, GIS and GPS could be implemented in real-time monitoring of plant disease [53], [54], [55], [56]. The localization using GPS is absolutely necessary for the realization of aerial and space remote sensing monitoring of wheat stripe rust.…”