Gene responsible for the purple skin of plums it's been identified

The presence and accumulation of the antioxidant pigment anthocyanin defines the tone of plums, and it is known that the synthesis of this compound is regulated by the MYB10 genes. Now, a research team from the Centre for Research in Agricultural Genomics (CRAG) and the Institute of Agri-Food Research and Technology (IRTA) has found the gene that determines the skin colour of Japanese plums. In a study published in the scientific journal Frontiers in Plant Science, the team reveals that the plum genome contains several copies of the MYB10 genes, and that DNA variations in one of these copies cause plums to have anthocyanins in the skin (showing a blue to red colour) or not (presenting a yellow or green tone). The Japanese plum, highly appreciated for its juiciness, is the most abundant plum on the market for direct fresh consumption, and Spain is one of its largest producers within the European Union, with plums grown mainly in Extremadura, Andalusia and Murcia. This new study provides a highly efficient tool for the early selection of coloured and non-coloured fruits in Japanese plum breeding programmes, an advance aligned with the objectives of the International Year of Fruits and Vegetables (IYFFV), designated by the UN General Assembly, to increase the efficiency of fruit food systems and promote healthy nutrition through fruit consumption. Anthocyanins: beyond colourThe red to blue tones of flowers and fruits are due to anthocyanins, a group of antioxidant pigments that promote flower pollination and protect plants from damage caused by light and dehydration. Incorporating these healthy antioxidants into our diet has been linked to anti-cancer and anti-inflammatory effects, and to the prevention of cardiovascular disease, diabetes and obesity. Apples, pears, peaches, apricots, plums, cherries and strawberries, all fruits of the Rosaceae family, are a valuable source of anthocyanins, contained in their skin and flesh. Given that fruit colour has an important impact on both consumer choice and nutritional quality, it is not surprising that there is considerable interest in breeding these crops for new varieties that produce fruit with diverse colours and shades, while promoting their enrichment in health-promoting compounds. Why Japanese plum?Within the rose cultivars, Japanese plum is among those with the greatest variation in fruit colours, including shades and patterns, with varieties ranging from green and yellow without anthocyanins to red, violet or blue. "Previous studies in rosaceae species show that anthocyanin synthesis and accumulation are regulated by MYB10 genes. Consequently, the analysis of these genes in multiple varieties of Japanese plum has proven to be an excellent model for understanding how fruit colour is determined," says  Arnau Fiol, PhD student at CRAG and first author of the paper. "In this study, we examined the MYB10 genes of a panel of Japanese plum varieties and found that they are highly variable. Surprisingly, we found that some cultivars have three copies of one of the MYB10 genes, which adds even more difficulty to the already complex analysis of plum colour variation," explains  Maria José Aranzana, IRTA researcher at CRAG in charge of this work. "By studying how these genetic variants are inherited, we have been able to identify which combinations of variants are associated with fruit skin colouring with anthocyanin (red to blue) and without anthocyanin (green or yellow)," she adds. Driving the development of new varietiesImagine we want to develop a new variety of blue plum with lots of anthocyanins to benefit from its nutraceutical properties. New varieties of fruit trees are bred in breeding programmes by crossing individuals and screening the hundreds or thousands of offspring for those with the desired trait, in this case a bluer plum, and which also meet demanding product quality standards. It can take 10 to 20 years from the first cross to the registration of a new variety, as fruit trees take a long period of time to bear fruit (around 3 to 4 years for plum trees) and must undergo several thorough evaluations. "In our work, we have identified the genetic variants that cause anthocyanins to accumulate or not in the skin of Japanese plum. This means that by simply studying the DNA of newly germinated seedlings, we can efficiently predict the skin colour of their future fruits, allowing us to quickly rule out all seedlings that will produce green fruits. Thanks to this early screening, we would need a smaller cultivation area and fewer resources (water, nutritional, phytosanitary and human) to obtain the desired new variety of plum rich in anthocyanins, with the consequent economic and environmental benefits," says Aranzana. The reliable molecular marker for early selection of coloured and uncoloured Japanese plums developed in this research can be effectively used in breeding programmes. Anticipating at seedling level the fruit colour that trees will produce after 3-4 years significantly shortens and optimises the breeding process. Since the mechanism underlying fruit colour variation is conserved within the Rosaceae family, this tool offers promising prospects for anthocyanin-determined fruit colour selection in other related species of agronomic interest. Reference article:Frontiers in Plant Science, Volume 12, Article 655267. 08 June 2021.  https://doi.org/10.3389/fpls.2021.655267 Characterization of Japanese Plum (Prunus salicina) PsMYB10 Alleles Reveals Structural Variation and Polymorphisms Correlating With Fruit Skin Color. Arnau Fiol, Beatriz E. García-Gómez, Federico Jurado-Ruiz, Konstantinos Alexiou, Werner Howad and Maria José Aranzana. About the CRAGThe Centre for Research in Agricultural Genomics (CRAG) is a centre that is part of the CERCA system of the Government of Catalonia, and was established as a consortium of four institutions: the Spanish National Research Council (CSIC), the Institute of Agri-Food Research and Technology (IRTA), the Autonomous University of Barcelona (UAB) and the University of Barcelona (UB). CRAG's research extends from basic research in plant and farm animal molecular biology to applications of molecular techniques for breeding species important for agriculture and food production in close collaboration with industry. Since 2016, CRAG has been recognised as a "Severo Ochoa Centre of Excellence in R&D" by the Spanish Ministry of Economy and Competitiveness. About IRTAIRTA (Institute of Agri-Food Research and Technology) is a research institute dedicated to agri-food R&D&I in the fields of plant production, animal production, food industries, environment, global change and agri-food economics. The transfer of its scientific advances contributes to the modernisation, competitiveness and sustainable development of the agricultural, food and aquaculture sectors, to the provision of healthy, quality food for consumers, and to improving the well-being of the population. IRTA is attached to the Department of Climate Action, Food and Rural Action (DARP) of the Generalitat de Catalunya and is part of the CERCA system. ImageJapanese plums show a wide variety of skin and flesh colours, both in tone and pattern, ranging from green and yellow with no anthocyanins to anthocyanin-rich red, purple and blue. Credit: CRAG-IRTA.