Few North American legumes are available for use in rangeland revegetation in the western USA, but Searls prairie clover Dalea searlsiae (A. Gray) Barneby is one that holds promise. Commercial-scale ...seed production of this species could address the issues of unreliable seed availability and high seed costs associated with its wildland seed collection. To evaluate its utility for revegetation, we collected Searls prairie clover at 20 locations across Utah and Nevada. Amplified fragment length polymorphisms (AFLP) and morphological and phenotypic traits (measured in common-garden plots) were used to clarify the role of evolutionary forces responsible for its genetic structure. Collections were evaluated for dry-matter yield, inflorescence weight, number of inflorescences, plant height, foliage diameter, flowering date, acid-detergent fiber, neutral-detergent fiber, and crude protein at two common-garden locations in northern Utah. Collections from southern Utah and eastern Nevada exhibited high phenotypic values, whereas collections from western Nevada and northwestern Utah had low phenotypic values. Collections from northwestern Utah were genetically differentiated from those of southern Utah and Nevada via AFLP markers. Strong isolation by distance between collections suggests that genetic drift and gene flow are important factors in determining population structure in Searls prairie clover.
Plant ovules provide zygotes with a physicochemical environment that supports embryo differentiation, growth, and maturation. The exact nature of this embryogenesis-enabling environment is not well ...characterized, as evidenced by failed attempts to induce normal embryony from zygotes or proembryos (precotyledonary) on defined media. To identify factors required for cotton (Gossypium hirsutum L.) zygotic embryony in vitro, we previously performed chemical and dissolved oxygen tension analyses of cotton ovule fluids and tissues at multiple stages of embryony in situ. Based on these analyses, we report herein the development of procedures that normalize embryo differentiation, growth, maturation, and germination in vitro, starting with proembryos. Our medium differed from Murashige and Skoog (MS) medium as follows (percentage of MS): N (30%, mostly from ten amino acids), P (815%), K (237%), Mg (85%), Ca (267%), S (506%), Fe (88%), and myoinositol (883%). Levels of other MS nutrients and vitamins, except sucrose, were kept at MS levels. Additionally, we included 100 mg L —1 casein hydrolysate plus the following (mmol L —1 ): D-glucose (1.8), fructose (4.7), sucrose (62.0), arabinose (7.1), melibiose (3.5), malic acid (11.6), and citric acid (3.8). Mannitol was added to achieve a medium osmotic potential of —1.10 MPa, and an atmospheric O 2 tension of 3.3 mol m —3 at the surface of embryos was maintained during culture. When cultured on medium containing 8.0 μmol L —1 indole-3-acetic acid, 80—90% of proembryos (as small as 100 cells) of cultivars HS-26 and B-27 increased four- to eightfold in surface area during the first 18 d in culture and germinated thereafter to produce viable plants. Increases in surface area of proembryos cultured on a modified MS medium previously used for somatic embryogenesis were from 0.2- to 0.6-fold. The described embryo culture medium should be useful for studying nutritional and molecular aspects of early embryony and possibly for plant zygote transformation protocols.
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Few North American legumes are available for rangeland revegetation in the semiarid western United States. Western prairie clover (Dalea ornata Douglas ex Hook. Eaton & J. Wright) is a perennial ...legume with desirable forage characteristics and is distributed in the northern Great Basin, Snake River Basin, and southern Columbia Plateau. Understanding the genetic and ecotypic variability of this species is a prerequisite for developing populations suitable for revegetation purposes. To address this need, we established two common-garden plots of western prairie clover from 22 sites in Idaho, Oregon, and Washington. Significant variation was detected among the collections for all traits measured. Among the measured traits, flowering date was correlated with collection-site temperature and elevation. Population structure estimates from 474 amplified-fragment length polymorphism markers resulted in two distinct, genetically differentiated groups and a third admixed group, and flowering date played a significant role in discriminating those genetic-based groupings of collections. Positive correlations were observed between phenotypic and genetic distance matrices (r = 0.33, P = 0.005), phenotypic and geographic distance matrices (r = 0.35, P = 0.002), and genetic and geographic distance matrices (r = 0.31, P = 0.009). Based on these results, we recommend that two germplasm sources of western prairie clover be developed for use across the collection area, one from the Deschutes River region and the other encompassing Idaho, Washington, and eastern Oregon collection sites.
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