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Simple Sequence Repeat (SSR) markers developed in apple and pear were used to determine genetic relationships among heritage apple and pear cultivars from Portugal's Azore Islands, and to develop identity fingerprints for European and Asian pear accessions at the USDA–ARS National Clonal Germplasm Repository (NCGR). We used 11 SSR markers (six from apple and five from pear) to examine 18 heritage apple and 9 heritage pear cultivars from the Azores. Eight additional Portuguese and economically important cultivars of apple and eight of pear were used as standards. Cluster analysis separated the apple and pear accessions into two distinct groups. Among apple genotypes, 12 unique accessions and five groups of synonyms were identified, while, in pear, seven unique genotypes and three pairs of synonyms were found. None of the accessions obtained from the Azores corresponded to widely grown standard Portuguese apple or pear cultivars. To examine 144 NCGR pear accessions, we used nine polymorphic SSR loci that were developed from GenBank sequences. Cluster analysis identified five sets of synonyms (four in P. communis L. and one in P. ussuriensis Maxim.) and four pairs of homonyms (three in P. communis and one in P. pyrifolia Burm. f. Nakai), and confirmed three clonal sets. Morphological evaluations and additional SSR markers will be used to confirm these results, and to genetically document the identities of pear genotypes. SSR markers will greatly assist the management of ex situ pome fruit germplasm collections by helping to eliminate duplicate accessions and expanding the genetic diversity represented.
Powdery mildew (Sphaerotheca mors-uvae) severely infects young shoots and leaves of black currants (Ribes nigrum) and red currants (R. rubrum) in the Pacific northwestern U.S. Environmentally sound control measures are being sought as alternatives to sulfur or demethylation-inhibiting fungicides. This study examined the effect of mineral oil spray on powdery mildew infection in susceptible black and red currants. Mineral oil at 8 mL·L-1(8000 ppm) was applied to plants until runoff at 0-, 2-, and 4-week intervals from April through June in 1999 and 2000 on eight currant cultivars growing in Corvallis, Ore. Shoot and leaf surfaces were rated for powdery mildew incidence in early July both years. Oil applications significantly reduced mildew severity in vegetative growth as compared with that of the unsprayed control. The disease control from 2-week interval and 4-week interval oil applications was not significantly different.
Powdery mildew (Sphaerotheca mors-uvae) severely infects young leaves and stems of gooseberry (Ribes uva-crispa) throughout the world. Environmentally friendly control measures are being sought as alternatives to sulfur or demethylation inhibiting fungicides. This study examined the effect of a mineral oil spray, the biological control agent Trichoderma harzianum Rifai strain T-22 (Trichoderma), a combination mineral oil + Tricoderma, and the chemical fungicide thiophanate, on powdery mildew severity in `Industry,' a susceptible gooseberry. Mineral oil at 8 mL·L-1 (1.0 fl oz/gal), Tricoderma at 4 g·L-1 (0.5 oz/gal) and thiophanate at 1.45 mL·L-1 (0.186 fl oz/gal), and mineral oil + Tricoderma mix was applied to plants until runoff at 2-week intervals from February 2002 through April 2002, on potted `Industry' plants growing in a greenhouse in U. S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore. The percent of infected leaves per plant were calculated and the percent of infected stem surface areas were visually rated in mid-April. The fungicide, mineral oil, and mineral oil + Tricoderma treatment applications significantly reduced powdery mildew severity inboth leaves and stems as compared with those of the unsprayed plants. The stem powdery mildew reduction levels of the mineral oil or a combination of mineral oil + Trichoderma treatments, were not statistically different than that of thiophanate, which is reported as commercially acceptable. We recommend mineral oil spray, or mineral oil + Tricoderma, as alternatives to fungicide control of powdery mildew on leaves and stems of young gooseberry plants.
A plant-collecting expedition to Iturup and Sakhalin Islands, Russian Federation, occurred between 21 July and 12 Sept. 2003. Actinidia, Rubus, Ribes, and Vaccinium, as well as seven accessions of strawberries, Fragaria L., were collected. Among them, a wild strawberry, Fragaria iturupensis Staudt, was collected on the eastern slope of Atsonupuri Volcano, Iturup Island, at 630 and 650 m elevation. This species was similar in habit, leaf color and overall appearance to the American strawberry species F. virginiana Mill. Fruits were bright red, oblate spherical, about 1.4 cm in diameter, and had exerted achenes. The native distribution of this species was limited to the middle elevation of the slope of this volcano, and only on Iturup Island. Chromosome counts indicated that these plants were octoploid. Initial DNA fingerprinting aligned this sample with other octoploid species. In addition to this species, samples of F. yezoensis H. Hara (syn. F. nipponica Makino) were collected on Kuibyshewskii Bay of Cape Otlivnoy, Iturup, and near Ujno-Sakhalinsk City, Sakhalin Island. F. iinumae Makino was observed in Ogon'ki Village, Sakhalin Island. This report confirmed the existence of F. iturupensis, the only known native Asian octoploid strawberry, and documented its limited range. Seeds of these strawberry species are available for research by request from the U.S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository in Corvallis.
Luther Burbank, the quintessential nurseryman of the early 20th century, remarked that small fruit was the “Cinderella of the pomological family.” He stated that although tree fruits had been improved to the point of an almost uncountable number of cultivars, it was the time and responsibility of his generation and those to follow to develop the small fruit for human consumption. Burbank had a penchant for detecting potential qualities of unusual plants and his broad association with plant explorers at the U.S. Department of Agriculture and elsewhere allowed him to examine diverse wild berry species. He obtained seeds of many small fruit species from throughout the world. He made wide crosses within and between these genera and species. Burbank selected and named many cultivars to be introduced through his nursery and elsewhere. He named and released ≈40 blackberries, raspberries (Rubus L.), and strawberries (Fragaria L.); four grapes (Vitis L.); and a hybrid Solanum that he named ‘Sunberry’. He sometimes exaggerated their descriptions for promotion or public recognition. For example, Rubus ×loganobaccus ‘Phenomenal’ was, he stated, “far superior in size, quality, color, and productivity…” to ‘Loganberry’. Unfortunately, this cultivar was not a commercial success. Burbank made a few crosses and sold what he considered to be improved species, e.g., ‘Himalaya Giant’ blackberry (R. armeniacus). He created new common names for foreign species, e.g., balloon berry (R. illecebrosus) and Mayberry (R. palmatus), to better market them. However, his amazingly keen observations of thornlessness, pigment diversity, and recognition of repeat flowering and fruiting in blackberries, raspberries, and strawberries, were insightful of the needs of future industry. Burbank was a disciple of Darwin and his theory of natural selection. Burbank’s classic breeding approach, to make wide crosses, produce large numbers of hybrid seedlings, choose significant seedlings with his traits of choice, and backcross to the desired parent for several generations, was successful, although he did not know of ploidy or gene recombination. Unfortunately, the ‘Himalaya blackberry’, now ubiquitous in hedgerows and fields throughout the Pacific Northwest in the United States, is designated as a federal noxious weed. Although not presently in commercial production, three of his Rubus cultivars (‘Burbank Thornless’, ‘Snowbank’, and ‘Phenomenal’) are preserved in the U.S. Department of Agriculture, National Clonal Germplasm Repository, in Corvallis, OR.
Core subsets have been formed in several clonally propagated crops; for pear (Pyrus), strawberry (Fragaria), mint (Mentha), currant (Ribes), blackberry (Rubus), blueberry (Vaccinium), apple (Malus), and pecan [Carya illinoinensis (Wangenh.) K. Koch]. Criteria for selecting entries into each core varies, as does the use each core receives. Core subsets have been selected for each of the major collections maintained at NCGR-Corvallis (pear, strawberry, mint, currant, blackberry, and blueberry). In general, core subsets include 10% of the full collection. Entries were selected on the basis of horticultural characteristics and species representation. Management of the collection is facilitated by recognition of core entries, which are frequently distributed. The 2500 accessions of the Malus collection are represented in a core subset of 200 accessions. Of those, 100 represent the 35 known species, while 100 accessions were selected from elite clones on the basis of horticultural characteristics. The core has been successfully used to find a superior virus indicator. Entries have been propagated in test orchards in five states. The core strategy was used to compare the pecan cultivar collection to seedlings from native populations throughout the species range. The analysis revealed gaps in the ex situ collection, and may have implications for in situ conservation. A core subset (26 cultivars) was selected by stratified sampling within the geographic regions to mirror the allele frequency of the cultivar collection, consciously including extreme expressions of each horticultural trait evaluated. The availability of the diverse subset has effected management and distribution.