Sorbus L. is a small genus of the family Rosaceae (subfamily Maloideae), comprising more than 80 species that are widely distributed in Asia, Europe, and North America. S. pohuashanensis (Hance) Hedl. is widely distributed in North China, Northwest China, and Northeast China. It grows on slopes or valley forests at altitudes of 900–2500 m and is resistant to low temperatures (Zhang et al., 2020). S. pohuashanensis provides considerable ecological benefits, such as attracting birds, thus increasing biodiversity (Fig. 1).

It has been recorded in the Chinese Materia Medica that Sorbus fruits relieve cough, resolve phlegm, and strengthen the spleen. In recent years, bioactive ingredients, including flavonoids, triterpenoids, anthocyanins, cyanogenic glycosides, and quinones, have been isolated from S. pohuashanensis and demonstrated to have potential health and medicinal values (Yu et al., 2017; Yin et al., 2019).

Because the color of its leaves, fruits, and flowers changes with season, S. pohuashanensis has attracted the attention of gardeners as an ornamental plant (Fig. 1). Scientists have tried to introduce S. pohuashanensis into the plains of China as a horticultural crop. However, in summer, when the plants are exposed to sunshine, necrotic spots are generated on the leaves, a phenomenon known as sunburn (Munné-Bosch and Vincent, 2019). Sunburn is one of the most serious problems facing the application of S. pohuashanensis and other plants. Sunburn can occur in many tissues and organs, such as fruits, leaves, and branches, and has been reported in Pyrus communis (Goodwin et al., 2018), Eriobotrya japonica, Malus domestica (Racsko and Schrader, 2012), Vitis vinifera (Rustioni et al., 2020), and Citrus reticulata Blanco (El-Tanany et al., 2019). Sunburn reduces crop yield and the ornamental value of crops, resulting in extreme economic losses to growers annually. It has been shown that the occurrence of sunburn is related to several meteorological factors such as light intensity, temperature, air humidity, and wind speed (Racsko and Schrader, 2012). However, little is known about the causes of sunburns in S. pohuashanensis.

Long-read sequencing technology has been used for many crops, such as rice (Du et al., 2017), maize (Jiao et al., 2017), and cotton (Yang et al., 2019), and has promoted basic and applied plant research. The genome sequences of domesticated apple (M. domestica) (Sun et al., 2020) and pear (P. communis), which belong to the subfamily Maloideae, have also been reported. The present study reports the reference genome for S. pohuashanensis, obtained using PacBio circular consensus sequencing and high-throughput chromosome conformation capture (Hi-C) technology. We resequence a core collection of Sorbus spp., mainly from China, and analyze their phylogenetic relationships. We also perform gene family expansion and comparative genomic and RNA-seq analyses to elucidate the possible mechanisms underlying the sunburn phenomenon.