Progress of collection, conservation and innovative utilization of Prunus mira resources in the National Qinghai-Xizang Plateau Crop Germplasm Repository (Lhasa)

The Prunus mira Koehne, a dicotyledonous plant of the Rosaceae family and genus Prunus, is native to Xizang and is also known as the Tibetan peach. In Tibetan, it is called Kangbo. It is a deciduous small tree, reaching a height of 4 to 10 meters. Its leaves are lanceolate or ovate-lanceolate. The flowers are solitary or in pairs, with a diameter of 2 to 2.5 cm, ranging from pink to white in color. The fruit is nearly spherical, with a diameter of 3 to 4 cm. The seed is ovate-elliptical, flat and smooth. The flowering period is from March to April, and the fruiting period is from July to September. The fruit can be eaten fresh or processed. The kernel contains up to 50% to 60% oil, which can be extracted for edible or industrial use. In traditional medicine, the kernel is believed to have the effects of promoting intestinal peristalsis, relieving constipation, and treating cough and asthma. It is both a wild peach species in Xizang and a unique tree species in China. In October 1910, the plant hunter Wilson collected it and brought it back to the Arnold Arboretum of Harvard University. Due to its distinctive smooth seed, it was named Prunus mira by Koehne, and this name has been used for this type of peach tree ever since. Prunus mira mainly grows in the Qinghai-Tibet Plateau at an altitude of 1700 to 4498 meters. The average annual temperature of the distribution area is 6 to 13 ℃, with an average temperature of -2 ℃ in the coldest month (January) and 18 ℃ in the hottest month (July). It is particularly abundant in the Nyingchi area of Xizang, which has an average altitude of 3100 meters. It is also distributed in the southwestern part of Sichuan Province (at an altitude of 2500 to 3300 meters). Through the detection of habitat and morphological indicators of Prunus mira, it was found mostly to grow in the loam or light sandy loam and sandy loam soil with a pH of 6.5 to 7.6. Most of the tree crowns are umbrella-shaped, with well-developed root systems, tall tree bodies, and long survival periods. According to historical records and local oral accounts, some trees can live for over a thousand years as a living fossil group of rare peach germplasm resources in the world. It is belived to be the origin ancestor of peaches in the world. It has excellent characteristics such as drought tolerance, cold resistance, poor soil tolerance, strong adaptability, disease and pest resistance, longevity, and strong fruiting ability. It is an excellent parent for peach hybridization and has ecological value in soil stabilization and water conservation. Through long- term investigation, collection and research on this very precious wild fruit tree germplasm resource, we have screened out germplasm resources with unique fruit characteristics in Qinghai- Tibet Plateau. They can be used for peach breeding. In scientific research, Prunus mira is an experimental subject for studying the origin of peaches. The strong adaptability of Prunus mira enable the species to be cultivated in large-scale by seedling propagation, so that it is ecologically valuable in soil stabilization and water conservation. In terms of economic benefits, the blooming of peach blossoms in large areas can create a beautiful scene for tourists. In the basic research of Prunus mira resources, a combination of seedling selection, field investigation, sampling and indoor analysis techniques as molecular marker technology and electron microscopy scanningis used. Our research group began studying Prunus mira in Xizang in 2009. Through extensive field investigations and sampling, we collected, investigated and sampled resources in Lhasa, Nyingchi, Xigaze, Chamdo and Ali during the flowering period, young fruit period and mature fruit period. Currently, there are research foundations for research on Prunus mira in many aspects. The large-fruited yellow-fleshed high-quality Prunus mira of Xizang was rated as one of the top ten excellent resources in China in 2019. So far, 20 accessions of high-quality Prunus mira resources with large fruits have been selected, the fruits can be used for fresh consumption or processing into dried walnuts and the trees can be cultivated for economic forest construction.