Project Details:

How does Phytophthora sojae evade detection by Rps genes in soybean

Parent Project: How does Phytophthora sojae evade detection by Rps genes in soybean
Checkoff Organization:Iowa Soybean Association
Categories:Soybean diseases, Breeding & genetics
Organization Project Code:
Project Year:2013
Lead Principal Investigator:Alison Robertson (Iowa State University)
Co-Principal Investigators:
Anne Dorrance (The Ohio State University)
Keywords: Genetic Resistance to Diseases, Phytophtora Root Rot, Phytophtora sojae, Virulence Genes

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Phytophthora root rot is primarily managed by planting varieties with genes that confer resistance. Fourteen Rps genes have been identified and four genes are currently used in commercial soybean varieties to provide resistance to the disease. The effectiveness of a resistance gene relies on its ability to recognize the pathogen's corresponding avirulence gene. The goal of this continuing project is to characterize the genetic changes that occur within the avirulence gene(s) of Phytophthora sojae that enable the pathogen to escape detection by the corresponding resistance gene.

Project Objectives

1. Assess the genetic diversity of avirulence genes Avr1a, Avra3a, Avr3c in populations of P. sojae from Iowa, Missouri, Ohio and South Dakota.
2. Evaluate if transposons contribute to diversity and activity in Phytophthora sojae.
3. Develop specific primers that could monitor key Avr loci in isolates of P. sojae for monitoring of pathogen shifts.
4. Assess the prevalence of the proposed "elite" effector genes within the Midwest population of P. sojae.

Project Deliverables

Progress of Work

Final Project Results

• The number of copies and transcription of Avr1a was determined in 88 isolates of P. sojae from Iowa and Ohio.
• The number of copies of the gene ranged from 0 to 2. Presence of the gene did not always indicate avirulence on Rps1a.
• Transcripts of Avr1a were detected in some strains but transcription did not necessarily indicate avirulence on Rps1a.
• The Avr1a locus of four representative isolates from OH was sequenced and genetic diversity was considerably greater than that previously reported.
• Four LTR retrotransposons (BEL) were found in proximity to the Avr1a locus
• Transcriptomic analysis of two cultivars without Rps genes inoculated with 5 different isolates of P. sojae is in progress, to compare the transcriptional changes that occur during the infection process from isolates with different combinations of Avr1a gene conformations.
• Previous research suggested deletion of Avr1a or loss of transcript resulted in virulence on Rps1a, in soybean. Our data suggest that there are other mutations playing a role in gain of virulence
• The genetic diversity of Avr1d within isolates from Iowa was assessed.
• A large deletion at either the 3’ or 5’ end of the Avr1d gene that contributed to virulence of Rps1d was detected. Previous published research indicated that deletion of the entire locus contributed to virulence. Therefore our data suggest that additional mutations may play a role.
• The data from this study are informing a current study (ISA funded project) The effect of rotations of host resistance genes (Rps) on pathogen avirulence genes (Avr) in the soybean-Phytophthora sojae pathosystem (2014-2016).

Benefit to Soybean Farmers

Performance Metrics

Project Years