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Disease Lesion Mimicry Caused by Mutations in the Rust Resistance Gene rp1
G. Hu1, T. E. Richter, S. H. Hulbert
1Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506.
Abstract:
The rp1 locus of maize controls race-specific resistance to the common rust fungus Puccinia sorghi. Four mutant or recombinant Rp1 alleles (rp1-NC3, Rp1-D21, Rp1-MD19, and Rp1-Kr1N) were identified. They condition necrotic phenotypes in the absence of the rust pathogen. These Rp1 lesion mimics fall into three different phenotypic classes: (1) The rp1-NC3 and Rp1-D21 alleles require rust infection or other biotic stimulus to initiate necrotic lesions. These alleles react strongly to all maize rust biotypes tested and also to nonhost rusts. (2) The Rp1-MD19 allele, which has a similar phenotype, also requires a biotic stimulus to initiate lesions. However, Rp1-MD19 shows the race specificity of the Rp1-D gene. (3) The Rp1-Kr1N allele specifies a diffuse necrotic phenotype in the absence of any biotic stimulus and a race-specific reaction when inoculated with maize rust.
Insights
Four mutant maize Rp1 alleles were identified, causing necrotic phenotypes. These alleles exhibit varied responses to rust pathogens, influencing disease resistance and plant immunity.
Area of Science:
- Plant genetics and pathology
- Maize disease resistance mechanisms
Background:
- The Rp1 locus in maize is crucial for controlling race-specific resistance against the common rust fungus, Puccinia sorghi.
- Understanding the genetic basis of plant-pathogen interactions is vital for developing disease-resistant crops.
Purpose of the Study:
- To characterize novel mutant and recombinant alleles at the Rp1 locus in maize.
- To investigate the phenotypic responses of these alleles to biotic stimuli, particularly rust pathogens.
Main Methods:
- Identification and characterization of four mutant or recombinant Rp1 alleles: rp1-NC3, Rp1-D21, Rp1-MD19, and Rp1-Kr1N.
- Phenotypic analysis of these alleles, focusing on lesion mimicry and responses to rust infection and other biotic stimuli.
Main Results:
- The identified Rp1 alleles condition necrotic phenotypes, acting as lesion mimics in the absence of the pathogen.
- These alleles were classified into three phenotypic groups based on their requirement for biotic stimulus and their reaction spectra to different rust biotypes.
- Rp1-NC3 and Rp1-D21 require biotic stimulus for necrosis and react broadly to maize and nonhost rusts.
- Rp1-MD19 also requires biotic stimulus but exhibits race specificity similar to the Rp1-D gene.
- Rp1-Kr1N displays a constitutive diffuse necrosis and a race-specific reaction upon inoculation with maize rust.
Conclusions:
- The study identified and phenotypically characterized novel Rp1 alleles in maize, revealing diverse mechanisms of plant defense.
- These findings contribute to understanding the complex genetic control of disease resistance and race specificity in maize-rust interactions.
- The characterized alleles provide valuable tools for further research into plant immunity and crop breeding for rust resistance.