Fruit scientific research in New China in the past 70 years:Plum

Abstract: China is the leading plum production country worldwide with a harvested area of 1 987 284 ha and a production of 6 804 399 t. Plum is the second largest deciduous fruit type following apple in planting area in China. Due to long growing history, wide eco-geographical distribution, unique complicated origin and domestication of plum, there are great diversity of plum germplasm resources in China,which is the important base for plum improvement and plum industry development for both China and the world. Plum genetic resources conserved or used in China include nine species such as Prunus salicina Lindl., P. ussuriensis Kov. & Kost., P. simonii Carr., P. cerasifera Ehrh., P. domestica L., P. spinosa L., P. americana Marsh., P. nigra Ait., and P. insititia L.. All the species except for P. domestica(both are hexaploidy), P. insititia(hexaploidy)and P. spinosa(tetraploid)are diploid. During the early years of the new nation, the research and utilization of plum resources dispersedly and sporadically appeared in few colleges or institutes. In 1980, the nationwide exploration, collection, conservation, characterization, evaluation and documentation, mainly based on botanical and agronomic traits, of plum genetic resources were launched funded by the former Ministry of Agriculture of China, and then the Chinese National Germplasm Repository for Plums was established in 1986, and China Fruit-plant Monographs:Plum Flora was published in 1998 based on the above-mentioned primary evaluation data. From 1990 s,physiological and biochemical techniques were used to further evaluate plum resources, including cold tolerance, disease resistance, isozyme pattern, etc.. With the entry of the new century, precise evaluation was waged for accession diversity, genetic relationship, phylogenetic analysis, and primary core collection, core collection, small core collection, micro collection, applied core collection e.g. backbone or key parent to breeding were defined of plum genetic resources based on multi-disciplinary approaches e.g. botanical, palynological, biochemical, and molecular biological protocols. The inherited tendency of main or concerned agronomic traits in plum and the correlation of characters between F1 and parents were analyzed using open or cross pollination populations in the early breeding experience mainly in northeast institute where plum cultivars were given more attention as many other fruit species can not grow well due to the cold temperature in winter. The plum cultivar evolution in China has gone through two stages. Local cultivars with strong aroma and good adaptability to local climate conditions had a soft flesh and poor appearance, while the introduced improved cultivars from west developed countries had firm flesh and attractive skin color but were tasteless and with poor resistance to low temperature or diseases(bacterial spot). The purpose of breeding efforts was made to combine advantages of the local and exotic cultivars and to breed cultivars for commercial growing with excellent flavor, firm flesh, attractive appearance and good adaptability to local conditions. Therefore, the breeding roadmap was figured out as the east crossing with the west equals to the best, with the integration of modern molecular biological technologies such as marker assistant selection, into traditional hybridization breeding programs. The research advances since the founding of the new China covers flower bud differentiation,pollination biology, photosynthesis, fruit development, stress physiology, postharvest handling, storage and processing techniques, which are also reviewed. Future priorities should be placed on the distinctive accessions collection, precise evaluation, association analysis based on phenotyping and genotyping, function marker development, key gene mining, control and regulation analysis of important economic traits, breeding for new cultivars specific to eco-geographical conditions, and R & D of plum physiology, growing and postharvest handling technology.