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Charles J. Simon and Richard M. Hannan

Core subsets have been selected for the USDA chickpea (Cicer arietinum), lentil (Lens culinaris), and pea (Pisum sativum) germplasm collections. These subsets are specifically intended to increase the efficiency of the utilization of the entire collections of these taxa. The cores consist of 13% of the 3873 chickpeas, 12% of the 2390 lentils, and 17.5% of the 2886 pea accessions. They were selected by a proportional logarithmic model, and also contain additional accessions based upon documented concentrations of diversity. Each core has been screened for disease reactions, and results suggest that the cores can effectively direct germplasm users toward portions of the entire collections that contain resistant germplasm. These cores have also been useful for those interested in assessing the adaptation potential of these crops in new environments, because the entire range of adaptation is represented. Although cores may not always enhance access to germplasm with unique or extremely rare characteristics, the legume cores have been very useful for directing users toward desirable germplasm from defined geographic areas, and assisting users at the preliminary stages of germplasm evaluation.

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Charles J. Simon and Richard M. Hannan

The USDA Pisum collection, currently consisting of 2881 P.I. lines, is in its third year of maintenance and distribution from the Pullman WA location, after being transferred from the Geneva. NY P.I. Station. It is our policy to distribute only material that is free of the Pea Seedborne Mosaic Virus. To that end 2300 of the lines have undergone an extensive virus cleanup program to verify infection status and provide virus free seed. Virus-free seed has been undergoing multiplication under greenhouse and screenhouse conditions in Pullman, and under field conditions at research station at Central Ferry, WA. Seed is now available for approximately 1700 lines. A two-year program to update descriptor information for the 19 most important descriptors identified by the Pisum CAC was initiated this summer. A pea core collection has been developed and is being examined for representative diversity with molecular markers.

The G.A. Marx genetic stocks collection was transferred to Pullman in February, 1994. Over 400 of the 500+ lines designated for that collection have been increased in Geneva, NY under greenhouse conditions and are currently available for distribution. A computer database describing this collection is near completion, as is a bound catalog that will be made available. Lines of the collection are being given P.I. numbers, and the database will be uploaded into the new version of the USDA GRIN computer system that should be on-line sometime in 1994.

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Charles J. Simon and John C. Sanford

A method is described for separating large and small pollen effectively from a heterogeneous mixture. This method potentially is applicable to separation of pollen grains of different ploidy levels, since “unreduced” 2n pollen is larger than normal pollen (n); it might then be used to increase the efficiency of a breeding program employing sexual polyploidization and to diminish crossing inefficiencies in interploid crosses.

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Charles J. Simon and Richard C. Johnson

Maintenance of genetic resources within the National Plant Germplasm System includes preserving the genetic constituency of accessions as close to the original sample as possible. Genetic changes that can arise during seed regeneration include both an overall loss of genetic diversity within heterogenous accessions and changes in the gene frequencies within accessions. Two germplasm collections are being examined with molecular methods at the Western Regional Plant Introduction Station (WRPIS) for evidence of such genetic change. In the case of pea, gross observation of seed and plant characters indicate that vigorous plant culling during a comprehensive Pea Seedbourne Mosaic Virus eradication program a decade ago resulted in the overall loss of genetic diversity in some heterogenous accessions. Isozyme data has corroborated these observations. Molecular markers are beginning to be used, both to quantify possible genetic changes in accessions as a result of the eradication process, and to document success in reintroducing diversity by repeating the eradication process with additional seed from archival seedlots. In the case of ryegrass, the practice of bulking the seed harvested from regeneration plots may bias the seedlot toward genotypes that are more fruitful. Isozyme analysis after two regeneration cycles showed that balanced sampling (equal seed no./plant) maintained allele frequencies close to the original seed sample. A bulk harvest sample and a sample with an equal number of spikes harvested from each plant showed some significant change in allele frequency, but no significant changes were seen in the allelic richness of accessions, or in the level of an accession's overall heterozygosity. A regeneration sample with an equal number of seed/plant will therefore best preserve gene frequencies within accessions, but loss of an accessions overall diversity will not diminish as a result of less than ideal sampling methods in ryegrass.

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Denys J. Charles and James E. Simon

The curry plant [Helichrysum italicum (Roth) G. Don in Loudon ssp. italicum or H. angustifolium (Lam.) DC (Asteraceae)], a popular ornamental herb with a curry-like aroma, was chemically evaluated to identify the essential oil constituents responsible for its aroma. Leaves and flowers from greenhouse-grown plants were harvested at full bloom. Essential oils were extracted from the dried leaves via hydrodistillation and the chemical constituents analyzed by gas chromatography (GC) and GC/mass spectrometry. The essential oil content was 0.67% (v/w). Sixteen compounds were identified in the oil and included: neryl acetate (51.4%), pinene (17.2%), eudesmol (6.9%), geranyl propionate (3.8%),β-eudesmol (1.8%), limonene (1.7%), and camphene (1.6%). While the aroma of the curry plant is similar to that of a mild curry powder, the volatile chemical profile of the curry plant does not resemble that reported for commercial curry mixtures.

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Hilde Nybom, Susan Gardiner, and Charles J. Simon

Individual-specific DNA fragment patterns were obtained by hybridization of endonuclease-digested apple (Malus ×domestica Borkh.) DNA with a probe (pAR72) derived from the rDNA spacer region of the `White Angel' crab apple. Fragment detection was carried out with a nonradioactive method, using a horseradish peroxidase-catalyzed luminol oxidation. Paternity could be inferred by comparison of the fragment pattern generated by a seedling with those derived from putative parents.

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Denys J. Charles and James E. Simon

Essential oils were extracted from leaves, flowers, and stems of Ocimum basilicurn, O. kilimandscharicum, and O. micranthum by solvent extraction, hydrodistillation, and steam distillation for essential oil content and the oil analyzed by GC and GC/MS for composition. While the yield of essential oil was consistently higher from steam distillation than hydrodistillation, a similar number of compounds was recovered from both hydrodistillation and steam distillation. Though the relative concentration of the major constituents was similar by both methods, the absolute amounts were higher with steam distillation. Essential oil content and composition varied by plant species and plant part. Essential oil content was highest in flowers for O. basilicum and in leaves for O. micranthum. No significant differences were observed in essential oil yield and relative concentration of major constituents using fresh or dry samples and using samples from 75 g to 10 g of dry plant tissue. While minor differences between hydrodistillation and steam distillation were observed, both methods resulted in high yields and good recovery of essential oil constituents. Hydrodistillation is a more-rapid and simpler technique than steam and permits the extraction of essential oil where steam is not accessible.

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Denys J. Charles, Amots Hetzroni, and James E. Simon

Recent developments in electronic odor-sensing technology has opened the opportunity for non-destructive, rapid, and objective assessment of food quality. We have developed an electronic sensor (electronic sniffer) that measures aromatic volatiles that are naturally emitted by fruits and fruit products. The ability of our sniffer to detect contamination in fruit juice was tested using tomato juice as a model system. Tomato juice was extracted from cultivar Rutgers and divided into eight glass jars of 300 g juice each. The jars were divided into two treatments: the control jars contained tomato juice mixed with 0.15% sorbic acid to suppress microbial growth, and the experimental jars contained only tomato juice. All the jars were placed open, on a counter top in the laboratory for 8 days. The juice was tested daily with the electronic sniffer and for pH. The total volatiles in the headspace of the juice was extracted on alternating days via dynamic headspace method using charcoal traps, analyzed by gas chromatography, and confirmed by GC/mass spectometry. The results indicate that the sniffer is able to detect differences between the two treatments 4 days after the tomato juice was exposed to ambient atmosphere. The electronic sniffer output for the control juice showed a monotonous decline, while the output for the experimental juice exhibited a sharp incline after day four. This sensor output correlated well with the total volatiles.

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Liangli Yu, Denys J. Charles, Jules Janick, and James E. Simon

The aroma volatiles of ripe fresh `GoldRush' and `Golden Delicious' apples (Malus ×domestica Borkh) were examined using dynamic headspace to capture the volatiles and gas chromatography (GC)–GC–mass spectroscopy (MS) analysis for compound identification. A total of 21 aroma volatiles were identified, with 16 being common to both cultivars: toluene, butyl acetate, hexyl formate, 2-methylbutyl acetate, xylene, butyl propionate, pentyl acetate, s-butyl butanoate, hexyl acetate, iso-butyl 2-methylbutanoate, hexyl propionate, hexyl butanoate, hexyl 2-methylbutanoate, hexyl hexanoate, a-farnesene, and ethyl phthalate. Three volatiles [dipropyl disulfide, pentyl 2-methylpropionate, and 2,6-bis(1,1-dimethylethyl)-2,5-cyclohexadiene-1,4-dione] were unique to `Golden Delicious'; two compounds (nonanal and nerolidol) were unique to `GoldRush'. Most identified compounds were esters. Hexyl acetate (18.39%) was the major volatile in `Golden Delicious', while butyl acetate (13.40%) was the highest in `GoldRush'.

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Liangli Yu, Denys J. Charles, Amots Hetzroni, and James E. Simon

The volatiles of muskmelon (Cucumis melo L. reticulatis cv. Mission) were sampled by dichloromethane extraction and dynamic headspace methods and analyzed by gas chromatography (GC) and GC–mass spectroscopy (MS). A total of 34 constituents were identified, with esters contributing 8%–92% of the total volatiles. Butyl propionate, ethyl 3-methylpentanoate, hexadecanoic acid, methyl (methylthio)acetate, propyl butyrate, phenylpropyl alcohol, and vanillin, were recovered only by solvent extraction, while hexanal was only detected using dynamic headspace sampling. Methyl butyrate 35.2%, ethyl acetate 17.1%, butyl acetate 11.6%, ethyl propionate 8.3%, and 3-methylbutyl acetate 6.3% were the major constituents by solvent extraction sampling method. Butyl acetate 35.5%, 3-methylbutyl acetate 20.9%, ethyl acetate 7.3%, 2-butyl acetate 5.6%, and hexyl acetate 3.8% were the major constituents recovered by headspace sampling. Fruit tissue was also separated into five layers (exocarp, outer mesocarp, middle mesocarp, inner mesocarp, and seed cavity) and the volatile constituents differed significantly in content and composition by tissue.