Contributions of Fusarium virguliforme and Heterodera glycines to the disease complex of sudden death syndrome of soybean.

Andreas Westphal,Dean Malvick,Lijuan Xing,Chunge Li,Alan Mckay

doi:10.1371/journal.pone.0099529

Abstract

BackgroundSudden death syndrome (SDS) of soybean caused by Fusarium virguliforme spreads and reduces soybean yields through the North Central region of the U.S. The fungal pathogen and Heterodera glycines are difficult to manage.Methodology/Principal FindingsThe objective was to determine the contributions of H. glycines and F. virguliforme to SDS severity and effects on soybean yield. To quantify DNA of F. virguliforme in soybean roots and soil, a specific real time qPCR assay was developed. The assay was used on materials from soybean field microplots that contained in a four-factor factorial-design: (i) untreated or methyl bromide-fumigated; (ii) non-infested or infested with F. virguliforme; (iii) non-infested or infested with H. glycines; (iv) natural precipitation or additional weekly watering. In years 2 and 3 of the trial, soil and watering treatments were maintained. Roots of soybean ‘Williams 82’ were collected for necrosis ratings at the full seed growth stage R6. Foliar symptoms of SDS (area under the disease progress curve, AUDPC), root necrosis, and seed yield parameters were related to population densities of H. glycines and the relative DNA concentrations of F. virguliforme in the roots and soil. The specific and sensitive real time qPCR was used. Data from microplots were introduced into models of AUDPC, root necrosis, and seed yield parameters with the frequency of H. glycines and F. virguliforme, and among each other. The models confirmed the close interrelationship of H. glycines with the development of SDS, and allowed for predictions of disease risk based on populations of these two pathogens in soil.Conclusions/SignificanceThe results modeled the synergistic interaction between H. glycines and F. virguliforme quantitatively in previously infested field plots and explained previous findings of their interaction. Under these conditions, F. virguliforme was mildly aggressive and depended on infection of H. glycines to cause highly severe SDS.

Highlights

Many diseases negatively impact soybean (Glycine max (L.) Merr.) production in major cropping areas [1]
Clear quantitative relationships for pure Fusarium virguliforme (Fv) DNA dilutions vs. values measured with the quantitative real-time PCR (qPCR) assay and for Fv DNA extracted from infested soil vs. values measured, as well as specificity testing, indicated a high potential for sensitive and specific quantification of F. virguliforme with this new assay
The relationship of conidia added to soil and cycle threshold (Ct) value was characterized by plateau of almost no detection followed by a clear quantitative response past a threshold level (Figure 2)

Summary

Introduction

Many diseases negatively impact soybean (Glycine max (L.) Merr.) production in major cropping areas [1]. While Heterodera glycines alone causes significant yield losses in most areas of soybean production in the U.S, [1], [7], [14], the synergistic interaction on a susceptible cultivar with F. virguliforme [15] appears to result in greater damage and requires additional efforts from plant pathologists to develop plant disease suppressing strategies. The management of SCN with crop rotation can be effective, but the crop rotation widespread in the North Central Region of the US of soybean with corn has not reduced SDS [18]. Sudden death syndrome (SDS) of soybean caused by Fusarium virguliforme spreads and reduces soybean yields through the North Central region of the U.S The fungal pathogen and Heterodera glycines are difficult to manage

Objectives

Methods

Results

Discussion

Conclusion