Advances in research on breeding and petal coloration mechanism of red-flowered strawberry

Abstract: The strawberry, belonging to the Fragaria genus of the Rosaceae family, is a perennial herbaceous plant with global significance as a berry fruit crop. Nearly all strawberry plants have white flowers. The red-flowered strawberry is a result of distant hybridization, which can be viewed in addition to fresh food due to its vibrant red flowers. China has a robust foundation in strawberry cultivation, and its area and yield ranks first in the world, which is of significant economic benefits. With the rapid development of China’s economy and the improvement of material level, people have higher and higher requirements for the selection of strawberry cultivars,“good-looking, delicious and healthy”is the current new demand for strawberry consumption. In recent years, red-flowered strawberries have garnered a global attention from scholars and breeders, which have coloration and morphological characteristics such as Pink Panda, Toscana, Pretty Beauty and Summer Breeze series. In addition, the red- flowered strawberry has a strong ability to reproduce; its green leaves, red flowers and red fruits have a high ornamental value, and can be used for landscaping and potted viewing. The red-flowered strawberry is highly popular due to its vibrant color and edible fruit, commanding a significantly higher market price compared to ordinary white strawberry cultivars, and thereby exhibiting immense and economic value. In China, the red-flowered strawberry can flower all year round in the southern region where the temperature is suitable, and in the cold northern region, it can also flower from April to October. Most red-flowered strawberries are not cold resistant, and its application in the open field in Shenyang area in China needs cold protection to overwinter, which seriously limits its growing area. Flower color is the main ornamental trait of the red-flowered strawberry, which is distinguished from cultivated strawberries with white flowers by its diverse petal colors, including gradients from light pink to deep red. There are many reasons affecting the formation of red color. The most important factor is the type and content ofpigments. The flower color of the red- flowered strawberry hybrid covers the whole red series, from light pink to red, which provides an ideal material for studying the mechanism of flower color formation. At present, there have been many studies on the molecular mechanism of petal coloration in redflowered strawberry. The results show that the structural genes of anthocyanin synthesis pathway and some MYB transcription factors play a role in flower color of red-flowered strawberry. In addition, molecular markers related to flower color of red-flowered strawberry have also been developed, which can effectively accelerate molecular breeding of red- flowered strawberry. Modern red- flowered strawberry breeding has a history of more than 60 years. With the joint efforts of breeders at home and abroad, new cultivars of red-flowered strawberry have come out continuously. At present, seed cultivars with different petal colors of red-flowered strawberry have been obtained, which will lay a good foundation for its popularization and application. The breeding of red-flowered strawberry cultivars in China started relatively late. Shenyang Agricultural University was the first institute to carry out the breeding of red-flowered strawberry in China. According to the different application goals of red- flowered strawberry, it mainly focused on the aspects of large fruit, high quality, bright color and good resistance. Now a series of red-flowered strawberry cultivars with different colors have been obtained. Some breeders obtained decaploid red-flowered strawberry through ploidy breeding, which showed strong plant resistance, large flower, strong reproduction ability and strong resistance. Currently, the majority of red-flowered strawberry cultivars in our country are single-petaled, and they are mainly propagated through asexual reproduction by using stolons. There is still a big gap compared with the cultivars cultivated abroad, especially in the Netherlands. Flower color, type and fruit quality are crucial traits that directly impact the ornamental and economic value of red-flowered strawberry. Therefore, in order to enhance the breeding efforts for red-flowered strawberry in China, it is necessary to broaden the genetic background by introducing excellent foreign cultivars as hybrid parents. This should be accompanied by extensive crossbreeding work and full utilization of abundant resources from related plants within China. Additionally, combining traditional crossbreeding methods with modern molecular biological techniques can cultivate superior red strawberry cultivars with independent intellectual property rights. Simultaneously, future efforts should focus on strengthening promotion and publicity of red- flowered strawberry to increase awareness suitable for both appreciation and consumption purposes. This will facilitate wider adoption of red- flowered strawberry among individuals and businesses. The present paper provides a comprehensive review on the origin, breeding history, current status of red-flowered strawberry, and the research progress made in developing new seed cultivars. Additionally, it delves into the molecular mechanism underlying petal color and explores the transcriptional regulation of red-flowered strawberry. The aim is to offer novel insights for breeding and germplasm innovation in red-flowered strawberry.