Guiltinan-Maximova Lab

For more than three decades, the Guiltinan-Maximova Lab at Penn State has been at the forefront of cacao science — combining fundamental plant biology with applied biotechnology to address some of the most pressing challenges facing the global cocoa industry. Our work centers on Theobroma cacao, the chocolate tree, a crop of profound economic and cultural significance that supports the livelihoods of millions of smallholder farmers across Latin America, Africa, and Asia. With annual global cocoa production valued in the hundreds of billions of dollars, yet threatened by disease losses estimated at 30–40% of yield, the need for rigorous, translational science has never been greater. Our research generates new knowledge in plant genomics, disease resistance, and biotechnology and translates it into tools and technologies that breeders, farmers, and industry partners can use — contributing to a more sustainable, resilient, and equitable cocoa supply chain. 

Core Research Areas

Our research spans the molecular to the field scale, with cacao at the center of every question we ask:

Genomics and the Cacao Gene Atlas — We co-led the first sequencing of the cacao genome and recently developed the Cacao Gene Atlas, a comprehensive transcriptomic resource that gives breeders and researchers unprecedented access to the genetic architecture of the chocolate tree.

Disease Resistance — Fungal and oomycete diseases, including Phytophthora black pod rot, cause catastrophic losses for cacao farmers worldwide. Our lab recently achieved the first heritable, non-transgenic disease resistance in cacao using CRISPR-Cas9 gene editing — a landmark result with direct implications for sustainable crop protection.

Somatic Embryogenesis and Propagation Biotechnology — We pioneered and optimized a somatic embryogenesis (SE) system for cacao that has been field-tested across multiple countries and commercially deployed at a scale of more than 74 million plants in Indonesia alone — the largest tree crop SE deployment in the world.

Genetic Transformation — Our lab developed the foundational methods for stable genetic transformation of cacao, holding two U.S. patents for transformation and SE systems, and introduced GFP reporter technology to non-model tree species for the first time.

Regulation of Gene Expression and Plant Development — We investigate the molecular switches governing cacao development, from embryogenesis to fruit maturation, providing the basic science foundation that underpins crop improvement strategies.

International Development and Sustainability — Our science is inseparable from its human context. Through projects including USAID's Cacao for Peace initiative in post-conflict Colombia, the Fine and Flavor Cacao program across six Latin American and Caribbean countries, and cadmium biology research protecting Peruvian smallholder exports, we work at the intersection of plant science, food security, and rural development.

Lab Description

The Guiltinan-Maximova Lab is co-led by Dr. Mark Guiltinan, Professor of Plant Molecular Biology and Director of the Penn State Program in the Molecular Biology of Cacao, and Dr. Siela Maximova, Research Professor of Plant Biotechnology and Director of Latin America and the Caribbean for Penn State Global. Together they bring complementary expertise — Dr. Guiltinan in plant molecular biology, gene expression, and crop biotechnology, Dr. Maximova in propagation systems, functional genomics, international development, and intellectual property — that makes the lab uniquely equipped to move discoveries from bench to field to policy.

The lab has been active at Penn State since 1991 and has built one of the world's leading cacao research programs, with funding from the National Science Foundation, USDA, USAID, the Gates Foundation, the Bezos Earth Fund, Mondelez Global, the American Cocoa Research Institute, and the U.S. Department of Energy. We are home to the Penn State Cacao and Chocolate Research Network and maintain active collaborations with universities, research institutions, governments, and industry partners across more than a dozen countries.

Our team includes graduate students, postdoctoral researchers, staff scientists, and undergraduate researchers. To date, the lab has mentored more than 23 Ph.D. scholars and 80 undergraduates, and has hosted visiting scientists from 18 countries. We are committed to inclusive, international training that prepares the next generation of plant scientists for careers in academia, industry, and global development.

We welcome inquiries from prospective graduate students and postdocs, industry and NGO partners, and potential collaborators. Please visit our Contact page to get in touch.