Evaluation of Simplicillium lanosoniveum as a Biological Control Agent

View the project final report

• 2009 annual report

Commodities

• Agronomic: soybeans

Practices

• Crop Production: application rate management, biological inoculants
• Pest Management: biological control, chemical control, integrated pest management
• Production Systems: transitioning to organic

The following is the resulting publication from the study "Evaluation of Simplicillium lanosoniveum as a Biological Control Agent." It was submitted to the journal Biocontrol on 6-16-11.

Abstract: Simplicillium lanosoniveum (van Beyma) Zare & W. Gams (order Hypocreales, family Cordyciptaceae) is an antagonistic inhabitant of uredinial sori (pustules) of soybean rust (Phakopsora pachyrhizi). In previous laboratory studies, co-inoculations with S. lanosoniveum and P. pachyrhizi resulted in urediniospores that failed to germinate and fewer disease lesions. In the present field study, we used quantitative real time PCR to monitor colonization of S. lanosoniveum in diseased, field-grown soybean. Following inoculation with conidial inoculum of the antagonist, the fungus colonized leaf surfaces when plants were infected with P. pachyrhizi, either in a latent stage of infection or with disease symptoms. However, when plants were inoculated before infection, there was no increase of DNA of S. lanosoniveum suggesting that the pathogen must be present in order for the antagonist to establish itself on soybean leaf surfaces. Furthermore, we documented significantly lower amounts of DNA of P. pachyrhizi and lower disease severity when soybean leaves were colonized with S. lanosoniveum.

Introduction

Soybean rust (SBR), caused by Phakopsora pachyrhizi authority, was first reported in Japan in 1904 and has since spread throughout Asia, Africa, and the Americas (Miles et al. 2008; Yorinori et al. 2005). Disease losses ranged from 10 to 90 %, though there are reports as high as 100% (Miles et al. 2008). SBR was first discovered in the US in 2004, where it quickly became established in the southeastern states (Schneider et al. 2005; Schneider et al. 2008; USDA). Yield losses have been reported between 35 and 40% in Louisiana and as high as 82% in Florida on susceptible varieties that were not sprayed with fungicides (Walker et al. 2011) (R. W. Schneider, D. R. Walker, personal communication).
Breeding efforts have yet to produce resistant cultivars (Hartman et al. 2005). Therefore, disease management studies have focused mainly on fungicide applications. These studies showed that preventative applications of protectant fungicides must be accurately timed and applied very early in the infection process for effective control of the disease (Schneider et al. 2008). This may lead to unnecessary fungicide applications, especially throughout the southern US, because growers fear rapidly escalating epidemics such as those seen in Africa and Asia.
An antagonistic fungus, Simplicillium lanosoniveum (van Beyma) Zare & W. Gams (order Hypocreales, family Cordyciptaceae), which colonized uredinial sori (pustules) of SBR and penetrated urediniospores was discovered in 2007 in soybean from Louisiana and Florida (Ward et al. 2011; Ward 2009) (Ward Phytopath, accepted for publication). Using detached leaf assays, we observed a reduction in production of sori in the presence of S. lanosoniveum as well as a significant reduction in viability of urediniospores. The objective of this study was to evaluate the effects of S. lanosoniveum under field conditions. Development of S. lanosoniveum and the rust pathogen using quantitative real-time PCR (qPCR), as well as visual disease ratings were monitored.

The objective of this study was to evaluate the effects of S. lanosoniveum under field conditions. Development of S. lanosoniveum and the rust pathogen using quantitative real-time PCR (qPCR), as well as visual disease ratings were monitored.