Progress of collection, conservation and innovative utilization of watermelon germplasm resources in China

Watermelon (Citrullus lanatus, 2n =22) is a member of the Citrullus genus of the Cucurbitaceae, and is native to Africa. After its introduction to China, watermelon gradually spread throughout the country and numerous local varieties emerged. The watermelon area and production in China rank first in the world. In 2023, the watermelon planting area in China was about 1.49 million hectares, with a yield of about 63.96 million tons (FAO), accounting for 49.14% and 60.95% of the global total, respectively. China is also the world’s largest consumer of watermelon. In 2023, the per capita consumption of watermelon in China was 43.99 kilograms (FAO), which was 3.39 times the global level. Watermelon germplasm resources are the material basis for new variety breeding and scientific research, which provide an important guarantee for industry development. China attached great importance to the investigation, collection, and preservation of watermelon germplasm resources. China has established a medium- to long-term preservation, distribution, and utilization system for watermelon germplasm resources. The National Mid-term Genebank for watermelon and melon (Zhengzhou) was established in 2001 and mainly conserved the seeds of watermelon and melon resources. The primary responsibilities included collection, preservation, reproduction, identification, innovation and distribution of these germplasm resources. By December 2024, the National Mid- term Genebank for Watermelon and Melon (Zhengzhou) had collected and preserved 2600 watermelon accessions from 46 different countries in the world. These watermelon germplasm resources promoted the establishment of DUS testing standards for watermelon, breeding of new varieties, and basic scientific researches, such as genomics and origins, molecular markers, quality, disease resistance and so on. The achievements of these researches have contributed to crop improvement of watermelon and the promotion of the sustainable industry. This review presents an overview of the development history of the watermelon germplasms protection and summarizes the progress made since 2001 regarding watermelon germplasm collection and preservation, as well as their innovative utilization in China. Since 2001, the National Mid-term Genebank for watermelon and melon (Zhengzhou) has provided more than 1000 watermelon accessions to 57 national or provincial research institutions, 25 agricultural or comprehensive colleges, and 42 breeding companies, distributed in 25 provinces of China. The top five were Heilongjiang Province, Hunan Province, Xinjiang Uygur Autonomous Region, Henan Province and Zhejiang Province. However, less than 20% of these watermelon accessions received feedback from the utilization, and new variety breeding was rare. Most new watermelon varieties are hybrid varieties, and the selection of backbone parents involves multi parent hybridization followed by multiple generations of self-pollination, making it difficult to trace the source of excellent traits. Moreover, the new variety involves intellectual property rights, which creates a difficult feedback situation. Therefore, we propose future research directions and focus on the watermelon germplasm resources, aiming to provide a reference for the effective utilization and industrial development of watermelon germplasm resources in China.