Collaborative research unravels the science of how French beans became the fleshy, delectable treat we know today

Global common bean production focuses on two main market classes; the dry beans and the French/snap/green beans. Unlike dry beans whose pods are tough and stringy, French bean pods are fleshy, tender, and completely lack pod strings, giving them the best culinary quality.  However, French bean varieties may sometimes spontaneously revert to their undesirable ancestral stringy state. Ms. Serah Njau and Dr. Esther Arunga from the Department of Water and Agricultural Resource Management, University of Embu, participated in a collaborative research led by Dr. Travis A. Parker and Prof. Paul Gepts of University of California Davis, to understand the genetics underlying the pod string reversion phenomenon in common beans.

The team found that the absence of fibrous pod strings in French beans is associated with some DNA sequence features of a gene known as INDEHISCENT (“PvIND”). Specifically, these changes include a spontaneous duplication of the gene, accompanied by the insertion of a mobile DNA sequence. These features are lost through a shuffling process during pod reversion to a type with strings. These findings provide possible genetic solutions that would be valuable commercially as well as scientifically, in that they could maintain the absence of strings in French beans and prevent the reversion to a dry bean pod type.

The project was an international collaboration between researchers in five countries. Other project members were: Jose Cetz, Lorenna Lopes de Sousa, Saarah Kuzay, Sassoum Lo, Talissa de Oliveira Floriani, Jorge Duitama, Judy Jernstedt, James R. Myers, Victor Llaca and Alfredo Herrera-Estrella, from different institutions in the U.S., Colombia, Mexico, and Brazil, including the University of California Davis (USA); National Laboratory of Genomics for Biodiversity (Mexico); Universidade de São Paulo, Piracicaba (Brazil); University of Embu (Kenya); Universidad de los Andes, Bogotá (Colombia); Oregon State University (USA); and Corteva Agriscience (USA).

The research was funded by Clif Bar/Seed Matters, Lundberg Family Farms, Kirkhouse Trust, UC Davis Henry Jastro Graduate Research Scholarships, the Universidad de los Andes FAPA initiative, CAPES Postdoctoral Program, UC MEXUS, and USDA-NIFA Regional Hatch project.

This article is a summary of a published paper entitled ‘‘Loss of pod strings in common bean is associated with gene duplication, retrotransposon insertion, and overexpression of PvIND’’ published in the New Phytologist and available using the following link: