Introgression of Prunus Plums have great potential as a species in Plum commercial crop in regions outside of W. R. Okie California. The wide United States Department of Agriculture - Agricultural Research range of native plum Service, Southeastern Fruit and Tree Nut Research Laboratory, species provides an 21 Dunbar Road, Byron, GA untapped source of genetic material. Results from hybridizations are “ ntrogression” is a big word meaning Origin introduction of the genes of one very unpredictable. This Ispecies into the gene pool of another. The ancestors of what we call paper describes some of This transfer can be a one-time thing, or Japanese plums actually originated in Figure 18. Apple mosaic virus is common on the Fuji variety. Figure 19. Bridge grafting is used to overcome if one parent is much better than the other, China. The term “Japanese plum” this intriguing girdling caused by Valsa mali cankers. it may involve repeated backcrossing of originally was applied to Prunus salicina germplasm maintained an interspecific hybrid with one of its imported from Japan in the late 19th parents (generally the one with better century, but now includes all the fresh at Byron, GA., and In Shandong province, we noted We were surprised to see so few some differences of opinion, and many fruit). Within Prunus, plums have had the market plums developed by intercrossing summarizes our efforts that tree trunks and scaffold limbs were pests in the orchards that we visited. It “what if” questions. However, none of most extensive mixing and matching of various diploid species with the original severely affected by Botryosphaeria appears that pest control technology in us would deny that China and Chinese species. Use of exotic species for the other species. Most plums are diploid (two sets to collect it and use it in species, fungi that cause roughened China is far more advanced than the apple producers will have a huge impact main stone fruits – peach, cherry, almond of chromosomes) except for the European scaly bark with superficial blister-like horticultural technologies being on the U.S. apple industry over the next and apricot – has been minimal and plums which are hexaploid (six sets). scion and rootstock pustules in the outer bark. These fungi employed by Chinese apple growers. decade. It will be interesting to see how mostly directed at rootstock develop- These plums were initially improved by development. are also common in some NY orchards. those impacts develop and what ment. So I will primarily address species selection in Japan and later, to a much Their impact on productivity is Marketing and Export directions they will take. mixing as it relates to plums, specifically greater extent, in the United States. unknown. However, the trunk lesions Japanese plums. apparently can produce inoculum that In 2004 China became the number In China, P. salicina may have California cultivars because of its firm can cause fruit infections after bags are one fresh apple exporter in the world. Most of these Japanese plums are originated in the Yangtze River Basin but flesh and strong flavor. Chinese botanists removed prior to harvest. Preharvest The 775,000 metric tons they exported Steve Hoying is an Area Extension Educator consumed as fresh fruit. Production in the now is found across eastern China. The describe it as native to North China, and and postharvest fruit decays caused by just edged out France, and is about 50 % in orchard management for the Lake Ontario United States is concentrated in Califor- history of ‘Zhui Li’ cultivar goes back 2500 occasionally cultivated. It has some Botryosphaeria species cause severe losses above the U.S. fresh apple exports. This Fruit Region of New York State. Dave nia, where they are best adapted. Com- years. Numerous local selections have characters reminiscent of apricot and was in some parts of China amount is still less than 8 % of their total Rosenberger is a research and extension mercial production in California is domi- since been developed, but plum has never thought by some to have descended from production, which is a lower percentage professor at Cornell’s Hudson Valley nated by a few major cultivars, and new been as important in China as peach, a natural hybrid, but more likely is just In Shanxii province, we saw than the U.S., but still is an earth shaking Laboratory and leads Cornell’s research and cultivars become important only slowly. either commercially or culturally. Plums an upright variant of P. salicina. numerous orchards devastated by Valsa number. Even though much of this fruit extension program in plant pathology. There are few breeding programs outside in Southern China are concentrated in mali, a fungal disease of apples that is is second class quality destined for George Lamont is a recently retired California, where the primary goals of seven provinces, but especially in Fujian Plum stones have been found in similar, both in terms of the pathogen Mongolia and Russia, China also has Executive Director of the New York State increased size, firmness and quality have and Zhejiang, with over 20 million plum Japan dating back to the Yayoi Era, about and epidemiology, to our cytospora high quality apples going to the EU and Horticultural Society, and a fruit grower in required no further use of primitive trees found there and about 200 cultivars 2300 years ago. Japanese books dating canker disease on peaches. The canker other quality driven markets. Desmond Orleans County. germplasm. Recent utilization of genetic grown. Truly wild stands are rare but are back 1500 years mention cultivated problem in Shanxii has been exacerbated O’Rourke, publisher of the World Apple resources of Japanese plum has been lim- reported to still occur in Hubei and plums. Plums have been common garden by the severe pruning and regular Report, predicts China’s exports could ited in the United States compared with Yunnan, where some trees in Zhongdian plants in Japan for centuries, but girdling of the trunk and major scaffolds. double in the next few years. that of many other crops. Difficulties in County are over 100 years old. Low improvement efforts have only taken In addition, they have gradually collection, importation and quarantine chilling types of P. salicina are found in place in the last century. Plum culture in removed lower scaffold limbs in this None of us can predict how world through-put have limited the germplasm Southern China and Taiwan. Cold hardy Japan and also Korea is very ancient, so province as they allowed trees to grow events will unfold over the next decade, available. Prunus is more difficult to pre- plums in Northern China have been that it is not possible to tell for certain if taller in an effort to improve the next year, or even the next day. Those serve because of the large amount of space classified as P. ussuriensis and P. the countries were ever part of the native productivity. The severe pruning and of us on the IFTA tour had an interesting needed compared to small fruit crops, and gymnodonta, but are otherwise very range for plums. girdling weakened trees and the removal glimpse of China as an apple producing the shorter life of trees relative to other similar to P. salicina. Modern breeding of lower scaffold limbs provided ideal country and as an emerging world tree crops because of disease and insect programs, especially in USSR., have Plum Breeding - California entry points for Valsa mali. Their solution power. Nevertheless, it was only a problems. Lack of suitable rootstocks has utilized this source of hardiness (Okie and has been to bridge-graft around the glimpse, and that glimpse was limited also reduced tree life. The trend toward Weinberger, 1996). Trees of improved P. salicina cankered areas. Some trees with trunks to a short time period and a relatively fewer breeding programs, most of which cultivars ‘Kelsey’ and ‘Abundance’ were 5-8 inches in diameter had four or five small area of a huge country. We came emphasize “short-term” commercial va- Prunus simonii was described based introduced into the United States from bridge grafts of various ages (Figure 19). away with some common observations, riety development to meet immediate in- on cultivated specimens by Western Japan over 100 years ago. Luther Burbank dustry needs, has also contributed to re- botanists. This species (probably the same himself imported a second lot of Japanese duced use of exotic material. clone each time) was used in developing plum seedlings and from them named 20 NEW YORK STATE HORTICULTURAL SOCIETY NEW YORK FRUIT QUARTERLY • VOLUME 14 NUMBER 1 • 2006 29 perimeter. The sprayers were mounted ‘Burbank’ and ‘Satsuma’. He then Superior Farms) have named ‘Black (1989). While most have improved disease in the bed of a tricycle truck about the intercrossed these and other imports with Diamond,’ ‘Black Flame,’ ‘Black Gold,’ resistance, only ‘AU-Rubrum’ has size size of a John Deere Gator, and spray P. simonii and North American species, ‘Black Torch’ and ‘Sweet Rosa.’ Their and firmness adequate for commercial tanks usually consisted of a 30-gal or 50- resulting in ‘Beauty,’ ‘Duarte,’ ‘Eldorado,’ program is the largest of the private shipping. ‘AU-Amber’ is very sweet for gal drum (Figure 17). ‘Formosa,’ ‘Gaviota,’ ‘Santa Rosa,’ ‘Shiro,’ breeders, and as with most private an early plum, but crops erratically. and ‘Wickson’ (Howard, 1945). These programs, the releases are patented (Okie Breeding has been discontinued with the The predominant pest problems plums formed the basis for the world’s and Ramming, 1999). retirement of Norton. varied by location, but apple scab (black shipping plum industry, and some are still spot), rust diseases, and Alternaria leaf widely grown.