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- Author or Editor: Barbara Hellier x
The USDA-ARS National Plant Germplasm System is charged with the preservation of economically important crop plants and their wild relatives. Curators in the System strive to develop collections capturing the genetic diversity of each species. One mechanism for filling gaps in collections is through plant exploration. The USDA-ARS National Germplasm Resources Laboratory, Plant Exchange Office administers funding and coordinates plant explorations for the System. In the past decade, there have been 38 collecting missions in Central Asia and the Caucasus. This area is rich in plant biodiversity and is a center of diversity for many crop species and their wild relatives. The author has had the opportunity to participate in four explorations in the area focusing on wild crop relatives. This included a trip to Kazakhstan targeting Russian dandelion, Taraxacum kok-saghyz L.E. Rodin, a source of natural rubber. In this mission, a total of 22 accessions of T. kok-saghyz and six accessions of other Taraxacum species were collected.
The fruit of several Opuntia species (prickly pear) are a good source of calcium, potassium, and ascorbic acid and are consumed fresh or processed as juices or preserves. Plants of Opuntia may be grown in arid and semiarid environments on marginal soils. Various cultivars, particularly in the species Opuntiaficus-indica, are grown commercially in the United States, Israel, Italy, Mexico, and South Africa. There is a need for new sources of genetic diversity and subsequent germplasm evaluation, and until recently, no publicly maintained germplasm collection of Opuntia existed in the United States. The purpose of this study was to evaluate fruit quality of 25 Opuntia accessions, originating from six countries, and maintained at the USDA collection at the National Arid Land Plant Genetic Resource Unit, Parlier, Calif. The largest fruits were harvested from plants of accessions PARL 201, 202, and 228 (227.6, 247.3, and 231.3 g/fruit, respectively). The hardest peel was on fruits of PARL 225 and 234 (both 3.7 kg), and fruit pulp of the same two accessions had the highest firmness (2.3 and 2.4 kg, respectively). Soluble solids in mature fruit varied from 6.1% (PARL 231) to 15.0% (PARL 254). The fruit color ranged from light yellow through orange, pink to dark purple. These characteristics and other traits such as fruit acidity, presence of spines, and seed mass/fruit indicated that the material represents a diverse germplasm collection, usable for future cultivar development.
The USDA garlic (Allium sativum and Allium longicuspis) collection is maintained at the ARS, Western Regional Plant Introduction Station (WRPIS) in Pullman, Wash. This collection comprises 269 accessions, of which 153 are hardneck (flower producing) types. The fertility characteristics of these accessions was evaluated in the field at Pullman, Wash. After the spathes opened, bulbils were removed from all the evaluated accessions to facilitate flower development. The umbel and flower characteristics taken were anther color, flower color, flower shape, stigma position, flowers per umbel, umbel diameter, umbel shape, umbel defects, bulbil size, bulbil color, ease of bulbil removal, spathe opening, pollen production, and pollen viability. Of the 153 accessions, 10 produced only partial scapes with bulbils midstalk and no seed production capability. Viable pollen was shed in 85 accessions with viability ranging from 8% to 85%. Open-pollinated seed was generated by 19 of the Pullman, Wash., grown accessions. Seed production was low with yields from 6 to 91 seeds per accession.
Low temperatures can slow down emergence, decrease weed competitiveness, and lead to uneven crop maturity in direct-seeded crops such as baby leaf lettuce (Lactuca sativa L.). In this study, seeds of 103 single-parent lineage, homozygous lettuce accessions (53 cos and 50 leaf type) from the USDA National Plant Germplasm System (NPGS) and six commercial standard lettuce cultivars (three cos and three leaf type) were evaluated in replications for percent germination after 7 and 10 days at 5 °C in a germination chamber. Cos and leaf types were selected for this study as they are most commonly used for baby leaf lettuce production. Differences were observed among entries in percent seeds germinated after both 7 and 10 days. Overall, an average of 68% of seeds germinated after 7 days and 94% germinated after 10 days. Although several NPGS accessions had higher percent germination than the commercial cultivars, the average percent germination was not statistically different between the two seed sources at 7 or 10 days. Percent germination also did not differ between entries of cos and leaf type after 7 or 10 days. Similarly, no difference in percent germination between entries of dark and white seed color was observed after 7 or 10 days. No relationship between 100 seed weight and percent germination was observed after 7 days (r 2 = 0.07) or 10 days (r 2 = 0.13). Thus, lettuce seed type, color, and 100 seed weight do not appear to be good predictors of germination under cold conditions in lettuce. The accessions with the highest percent germination after 7 days at 5 °C have the potential to be used for the development of new lettuce cultivars suitable for an extended, early season production in temperate climates when soil temperature is lower than optimal for lettuce germination. Further studies are needed to assess the ability of these accessions to germinate rapidly under cold field soil conditions.