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By Biocat

A consortium of nine public and private research centers from Spain —with significant representation from Catalonia— has obtained the genome for the melon, a species with high economic value around the world. This is the first time that a public/private initiative in Spain has obtained the complete genome of a higher plant species (those that flower and produce seeds) Moreover, this has been done through new mass sequencing technology, which is cheaper and more efficient.

In addition to the complete melon genome, researchers have also sequenced the specific genomes of seven different varietals. The study has been published in the journal Proceedings of the National Academy of Sciences (PNAS).

The Melonomics project has been led by Dr. Pere Puigdomènech, of the Spanish National Research Council (CSIC), and Dr. Jordi Garcia Mas, of the Institute for Research and Technology in Food and Agriculture (IRTA), who both work at the Center for Research in Agricultural Genomics (CRAG). The project has also included an outstanding research group led by Dr. Roderic Guigó, of the Center for Genomic Regulation (CRG). Groups from Pompeu Fabra University, the CSIC Centre of Edaphology and Applied Biology of the Segura River, the National Genome Center (CNAG), the Polytechnic University of Valencia and the University of Wisconsin have also participated.

Funding for this work, totaling more than €4 millions, has been contributed by Genoma España, five autonomous communities (Andalusia, Castilla la Mancha, Catalonia, Madrid and Murcia) and companies Semillas Fitó, Syngenta Seeds, Roche Diagnostics, Savia Biotech and Sistemas Genómicos.

A step towards producing more resistant varietals

These results show that the melon genome has some 450 million base pairs and 27,427 genes, many more than its closest relative, the cucumber, with 360 million base pairs.

"We have identified 411 genes in the melon that can be related to disease resistance. That’s very few but, nevertheless, the melon is highly capable of adapting to different environments,” explains Pere Puigdomènech. During the study, when comparing this genome to others that are closely related philogenetically, scientists observed how changes occur to the genome of this species, which is known for its high variability.

Another question of interest in the study is related to the ripening of the fruit, a process that defines characteristics like taste and smell. Researchers have identified 89 genes related to this process: 26 linked with carotenoid accumulation (which gives the flesh color) and 63 with sugar accumulation and, thus, flavor. 21 of these hadn’t been described previously.

"This knowledge will allow us to improve this species genetically in order to produce varietals that are more resistant to disease and have better sensory quality,” points out IRTA researcher Jordi Garcia Mas.

Spain is the fifth largest melon producer in the world

Melon is part of the Cucurbitaceae family, which also includes species like cucumber, watermelon, squash and zucchini. Cucurbitaceae have small genomes. “It is a species of high economic interest, especially in countries in the Mediterranean, Asia and Africa. The diseases that affect this species, like the mosaic virus in cucumbers or fungi, can lead to significant financial losses. Therefore, the sequencing of this genome is expected to have a huge impact on improving this crop,” explains Puigdomènech.

According to 2009 data from the United Nations Food and Agriculture Organization, melon production worldwide totals 26 million tons per year. Spain is the fifth largest producer of melons and approximately one third of this production is exported, making it the largest exporter in the world.

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