Research

Doctoral Research

The Pennsylvania State University

Lab of Dr. Majid Foolad

Identification and mapping of new late blight resistance genes in the tomato wild tomato species Solanum pimpinellifolium

One of the most devastating diseases of tomato (Solanum lycopersicum) is late blight (LB), caused by the oomycete Phytophthora infestans, which can destroy an unprotected crop in 7 – 10 days. Host resistance of the crop can help reduce or eliminate the use of fungicides, although very little LB resistance has been observed in the cultivated tomato. However, strong resistance exists in the related wild species S. pimpinellifolium. A screening of 67 S. pimpinellifolium accessions identified 12 accessions with nearly complete LB resistance. For my research, I selected two of those accessions and hybridized each with an elite tomato breeding line to create two distinct genetic and breeding populations. Heritability (h²) was measured/estimated using the response to selection equation, generation means analysis (GMA), and parent-offspring correlation analysis. Results showed heritabilities ranging from 0.60 – 0.86, suggesting that both accessions could be valuable resources for breeders looking to incorporate LB resistance into the cultivated tomato.

I also conducted quantitative trait loci (QTL) mapping to identify the gene(s) conferring LB resistance in these accessions. This was done through trait-based analysis by selecting individuals with extreme resistance and susceptibility in F₂ populations. Single nucleotide polymorphism (SNP) markers were identified and used to generate linkage maps and conduct QTL analysis. Multiple QTLs associated with LB resistance were identified in both accessions, most previously unknown. Additionally, I conducted preliminary backcross breeding to introgress LB resistance from the two wild accessions into the cultivated tomato using phenotypic selection. After multiple generations of cross-pollination and selection, LB resistance continues to be maintained at levels consistent with the LB-resistant wild parents. Meanwhile, progress has been made with shifting the phenotype of the interspecific progenies towards the cultivated parent and reducing the undesirable S. pimpinellifolium traits.

Publications

Sullenberger, M.T. and M.R. Foolad, 2024: Identification and mapping of QTLs for late blight resistance in the wild tomato (Solanum pimpinellifolium) accession PI 270442 via selective genotyping. Frontiers in Plant Science 15:1482241.

Sullenberger, M.T., M. Jia, S. Gao, H. Ashrafi, and M.R. Foolad, 2022: Identification of late blight resistance quantitative trait loci in Solanum pimpinellifolium accession PI 270441. The Plant Genome 15, e20251.

Sullenberger, M.T., M. Jia, S. Gao, and M.R. Foolad, 2018: Genetic analysis of late blight resistance in Solanum pimpinellifolium accession PI 270441: Heritability and response to selection. Plant Breeding 137, 89-96.

Sullenberger, M.T. and M.R. Foolad, 2018: Genetic Characterization of Late Blight Resistance in Solanum pimpinellifolium Accession PI 270442. Advanced Studies in Biology 10, 20.

Foolad, M.R., M.T. Sullenberger, and H. Ashrafi, 2015: Detached-Leaflet Evaluation of Tomato Germplasm for Late Blight Resistance and Its Correspondence to Field and Greenhouse Screenings. Plant Disease 99, 718-722.

Foolad, M.R., M.T. Sullenberger, E.W. Ohlson, and B.K. Gugino, 2014: Response of accessions within tomato wild species, Solanum pimpinellifolium to late blight. Plant Breeding 133, 401-411.

Post-doctoral research, Syracuse University

Lab of Dr. Eleanor Maine

The lab studies reproductive development in the soil nematode and model organism Caenorhabditis elegans. My research focuses on the genetics and epigenetics of proteins important for germ line development and maintenance, including those involved in DNA repair and meiosis. Histone modification (H3K9me2) is a major target of that work. For my projects, I’ve developed double-mutant, extrachromosomal array, and fluorescence-tagged strains via mating, plasmid injection, and CRISPR-Cas9, respectively. I also have extensive experience with plasmid ligation/transformation, co-immunoprecipitation, and confocal microscopy.

Publications

Kelley, L.H., I.V. Caldas, M.T. Sullenberger, K.E. Yongblah, A.M. Niazi, A. Iyer, Y. Li, P.M. Tran, E. Valen, Y.H. Ahmed-Braimah, E.M. Maine, 2024. Poly(U) polymerase activity in Caenorhabditis elegans regulates abundance and tailing of sRNA and mRNA. Genetics.

Sullenberger, M.T., L.H. Kelley, and E.M. Maine, 2020. PCR-based screening of small plasmid inserts. microPublication Biology.

 Yang, B., X. Xu, L. Russell, M.T. Sullenberger, J.L. Yanowitz, and E.M. Maine, 2019. A DNA repair protein and histone methyltransferase interact to promote genome stability in the C. elegans germ line. PLoS Genetics.

Sullenberger, M.T. and E.M. Maine, 2018. Simplified detection of a point mutation in C. elegans using tetra-primer ARMS-PCR. microPublication Biology.

Post-doctoral research, Children’s Hospital of Philadelphia (CHOP)

Lab of Dr. Marni Falk

As a member of the Mitochondrial Medicine Research Group, the lab partners with government, academia, and industry to understand the behavioral and biochemical changes that happen with mitochondrial diseases. I performed extensive drug testing to ultimately develop therapies for these diseases. For my work, I used the soil nematode C. elegans and human dermal fibroblasts as disease models. I developed several new nematode strains to study these diseases and performed cell survival assays on fibroblasts against panels of drugs.

Labs of Drs. Lan Lin and Yi Xing

Within the Center for Computational and Genomic Medicine, the Lin and Xing labs focus on RNA modifications in human disease, including cancer. The labs develop and apply high-throughput sequencing strategies and transcriptome engineering technologies to study the regulation and function of RNA modifications. As Lab Manager and researcher, I am involved in several projects that utilize a variety of techniques including Oxford Nanopore sequencing and single cell sequencing. I extract and sequence RNA from human cell lines and patient samples for downstream analysis.