Gene expression assays for identifying apple cultivar resistance to marssonina leaf blotch
Research service offering qRT-PCR-based gene expression profiling of defense-related genes (CYP, LYK4, CERK1, Beta-1,3-glucanase, Class III endo-chitinase) in apple cultivars to identify resistance to Marssonina apple leaf blotch (MLB), supporting genome-editing breeding programs for resistant cultivars.
Overview
This research offering provides molecular diagnostic services to identify apple cultivars with genetic resistance to Diplocarpon coronariae, the fungal pathogen causing Marssonina apple leaf blotch (MLB). MLB is a devastating disease that causes premature defoliation and fruit infection, heavily impacting organic apple production in the eastern United States, particularly affecting popular cultivars like Honeycrisp. By profiling the expression of key defense-related genes—including CYP, LYK4, CERK1, Beta-1,3-glucanase, and Class III endo-chitinase—this service enables apple breeders and genomics researchers to screen germplasm for resistance traits suitable for genome-editing and conventional breeding programs.
Technical specifications
Target defense genes and pathways:
- CYP (Cytochrome P450) – potential resistance or systemic acquired resistance (SAR) marker
- LYK4 (LysM domain receptor-like kinase 4) – pattern recognition receptor for fungal chitin
- CERK1 (Chitin elicitor receptor kinase) – key receptor in chitin-triggered immunity
- Beta-1,3-glucanase – pathogenesis-related enzyme targeting fungal cell walls
- Class III endo-chitinase – hydrolytic enzyme with antifungal activity
Validated methodology:
- Inoculation protocol using virulent D. coronariae strain at 10^6 CFU on potted Fuji and Honeycrisp trees
- Leaf sampling at 0, 2, 5, 8, 12, and 15 days post-inoculation
- RNA extraction and qRT-PCR quantification on Roche LightCycler 480 II
- Relative gene expression analysis following the Pfaffl (2001) method
- Over 50 pathogenicity-tested isolates from New York, Pennsylvania, and Virginia available
- Eleven cultivars previously evaluated under natural MLB infection pressure in 2020
Applications:
- Germplasm screening for MLB resistance in apple breeding programs
- Identification of candidate genes for genome-editing approaches
- Comparative analysis between resistant and susceptible cultivars
- Support for organic apple industry disease management strategies
Technology readiness level
This research is at Technology Readiness Level 4–5 (validated in laboratory and controlled environment). The team has established pathogenicity testing protocols, validated inoculation methods, and identified candidate defense genes. The proposed one-year study will optimize gene primers for qRT-PCR and conduct comprehensive expression profiling to confirm the role of these genes in MLB resistance. Funding is sought to support a Postdoctoral Associate to execute the validation work. The service is positioned to support immediate breeding and research collaborations with apple industry stakeholders, genomics companies, and academic breeding programs seeking molecular markers for MLB resistance.
About Virginia Tech
Virginia Polytechnic Institute and State University (Virginia Tech) is a comprehensive public land‑grant research university with broad graduate and professional programs and a strong industry orientation. An adjacent research and technology park links companies with faculty, shared labs, and prototyping resources, while facilities in the National Capital Region create a direct connection to federal partners and supply‑chain collaborators. Integration with a regional health system supports clinical research and translational pathways, and the statewide extension network enables field deployment and validation with industry and communities. Research is supported by competitive federal funding from agencies such as NSF, NIH, DOE, USDA, and the Department of Defense. A dedicated technology transfer office provides IP management, licensing, startup formation, and industry contracting support.
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