Green or cream-colored, warty or smooth, bitter or mild, long and thin or short and stubby: The diversity of bitter gourd, an important vegetable and medicinal plant, prompted researchers to explore the genome in search of answers about how domestication has—or has not—changed the crop over time.

Domestication—the process of evolution under human influence—in bitter gourd (Momordica charantia) is complex. Distinct human preferences prevented the fixation of major mutations responsible for trait evolution.

Yet, at the same time, human intervention produced large differences in fruit shape, color, size, taste and other plant characteristics between cultivar groups grown in different geographic locations.

Many studies of domestication focus on identifying single genes governing major effects in phenotype. In Long-read bitter gourd (Momordica charantia) genome and the genomic architecture of nonclassic domestication, published 27 May 2020 in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), a team of researchers including WorldVeg frequent collaborator Cheng-Ruei Lee from National Taiwan University assembled the chromosome-level genome of bitter gourd and investigated genomic changes under domestication.

Results indicate wild and South Asian cultivars diverged about 6,000 years ago, followed by the separation of the Southeast Asian cultivars about 800 years ago, with the latter exhibiting more extreme trait divergence from wild progenitors and stronger signs of selection for fruit traits.

Unlike some crops where the largest phenotypic changes occur between wild and cultivar groups, in bitter gourd large differences exist between two regional cultivar groups, likely reflecting distinct consumer preferences in different countries. The study highlights the importance of investigating such non-classic examples of domestication.

Hideo Matsumura, Min-Chien Hsiao, Ya-Ping Lin, Atsushi Toyoda, Naoki Taniai, Kazuhiko Tarora, Naoya Urasaki, Shashi S. Anand, Narinder P. S. Dhillon, Roland Schafleitner, and Cheng-Ruei Lee. 2020. Long-read bitter gourd (Momordica charantia) genome and the genomic architecture of nonclassic domestication. Proceedings of the National Academy of Sciences of the United States of America (PNAS). https://doi.org/10.1073/pnas.1921016117