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Maria M. Jenderek

Lesquerella (Brassicaceae) seeds contain high concentrations of hydroxyl fatty acids with long carbon chains, similar to imported castor oil. Although species within the genus are considered as an alternative oil crop, lesquerella plants have ornamental characteristics that may present a valuable landscape alternative for dry open spaces. Seeds of certain Lesquerella species are already a component of wild flower seed mixtures sold commercially. The purpose of this study was to describe ornamental aspects of selected accessions in the USDA Lesquerella germplasm collection maintained at the National Arid Land Plant Genetic Resources Unit. From 2003 to 2005, more than 140 accessions from 30 species were characterized for selected plant characteristics. The majority of lesquerella flowers were yellow, but some species, such as L. mcvaughiana, L. mexicana, L. ovalifolia, L. pallida, L. perforata, and L. stoniensis, had white flowers. Petal length ranged from 4 to 11 mm, and the number of flowers per an unbranched stem was from two to seven. While the duration of full bloom of many lesquerella plants was between 15 to 40 days, the full bloom of plants of 10 accessions lasted from 50 (PARL 166, L. argyrea; W6 20836, L. grandiflora; W6 20841, L. lasiocarpa) to 72 days (PI 596362, L. fendleri). Those traits make the plants suitable for planting in landscape borders, low hedges, or color patches. The main use of the USDA, NPGS Lesquerella germplasm collection (201 accessions) is in cultivar development of a new oil crop. However when considering the duration of bloom and the abundance of flowers, several accessions may be used as ornamental crops, especially in semi-arid and arid landscapes where water supply is limited.

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Maria M. Jenderek* and Richard Hannan

In California, rust (Puccinia allii) on garlic (Allium sativum) was not considered an economic problem until 1998, when a severe infection of the disease caused an average 51% reduction in yield throughout the state. The weight of harvested bulbs was 25% to 60% smaller than the average weight in the previous year, and soluble solids were reduced by an average of 15%. Until recently, garlic varieties that are resistant or highly tolerant to rust have not been grown in garlic production fields in California. Open pollinated progenies derived from 3 Plant Introduction accessions of the U.S. Dept. of Agriculture-Agricultural Research Service germplasm collection (PI 493099, PI 540315 and W6 12820) were inoculated with a suspension of urediniospores (1, 2 × 105/mL) isolated from rust infected garlic leaves obtained from production fields in Kings, Fresno and Yolo counties. Inoculations were carried out in a replicated experiment in the field under plastic covers, where 12 hours of misting was applied. The disease symptoms were scored on all leaves of the inoculated plants. The size of observed lesions varied from <1 to 280 mm2. Of the 118 plants evaluated, 9.3% had an average leaf area with rust symptoms of less than 1%. The majority of the plants (83.1%) had 1 to 5% of leaf area infected, and over 6% of plants had symptoms on 5 to 25% of their leaf surface. The highest number of plants with a low percent of rust symptoms on leaves was observed on progenies produced from PI 493099. While all maternal plants used to produce the seeds showed rust symptoms, the presence of progenies with ≤0.5% of leaf area infected indicated that a tolerance source to P. allii may exist in the A. sativum NPGS, germplasm collection.

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Maria M. Jenderek and Yayeh Zewdie

Until recently, there has been no large-scale production of true seeds in garlic (A. sativum L. and A. longicuspis L.). The recent discovery of male fertile garlic accessions stimulated research on the genetics and breeding of garlic. However, there is no information regarding the phenotypic characteristics of garlic populations generated from true seeds. We evaluated the first generation of sexually derived families of garlic for bulb and clove weight, number of cloves per bulb, flower stalk height, number of leaves, plant height, and days required to achieve bulb maturity. Significant variations were observed within and among families for these important traits.

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Maria M. Jenderek and Barbara Hellier

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.

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Maria M. Jenderek and Richard M. Hannan

Diverse garlic germplasm has proven to be essential for production of true seed. Yet, fertile accessions in garlic germplasm collections have not been characterized for breeders and researchers, and information on morphological characteristics associated with seed producing plants is very limited. The objective of this study was to evaluate reproductive characteristics and true seed production capacity in the USDA garlic germplasm collection. Most stable traits, such as flower stem appearance, opening ability of spathe, level of difficulty to remove bulbils, tepal color, umbel shape, and the number of flowers per umbel, were similar across populations evaluated. Other characteristics including position of stigma, tepal closure, pollen viability, time of flowering, scape senescence rate, and number of seeds produced by individual plants varied within accession evaluated. Of 47 accessions, 19 produced true seeds (from 48.5 to 1.5 seeds per plant) in the Central Valley of California. Seed production in the germplasm evaluated is adequate to initiate garlic breeding projects.

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Yayeh Zewdie, Michael J. Havey, James P. Prince, and Maria M. Jenderek*

Garlic has been propagated exclusively by asexual means since time immemorial. The recent discovery of male fertile garlic accessions allowed studies on genetics and garlic improvement. Single nucleotide polymorphism (SNP) and random amplified polymorphic DNA (RAPD) based genetic linkage map was developed for garlic using a segregating population derived from one plant of PI 540316. Progenies segregated for male fertility and other morphological characters. Distortion of segregation was observed for most of the markers. This was expected due to the segregation of recessive deleterious alleles present in the garlic genome. The map contained 23 loci distributed on five linkage groups. It covered 319 cM with the average of 18 cM between loci. Linkage with the male fertility (Mf) locus was established with SNP marker AOB155 (26.7 cM).

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Yayeh Zewdie, Michael J. Havey, James P. Prince, and Maria M. Jenderek

Garlic (Allium sativum L.) has been cultivated by asexual propagation since time immemorial. The discovery of male-fertile garlic accessions has opened a venue for genetic studies and improvement through sexual recombination. An S1 family of 84 plants was generated from a single male-fertile heterozygous plant from the U.S. Dept. of Agriculture Plant Introduction 540316 and used to identify the first genetic linkages in garlic based on single nucleotide polymorphisms, simple sequence repeats, and randomly amplified polymorphic DNAs. Thirty-seven markers formed nine linkage groups covering 415 centimorgans (cM) with average distance of 15 cM between loci; other 16 loci remained unlinked. A male fertility locus was placed on the map. This first genetic map of garlic is a seminal step toward the genetic improvement of garlic and eventual marker-assisted breeding.

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Maria M. Jenderek, Phil Forsline, Joseph Postman, Ed Stover, and David Ellis

Clonal woody crop germplasm collections often originate and are grown in distinct geographical locations. Because the degree of cold-hardiness is known to be a factor in the successful use of dormant bud cryopreservation for Malus, it was suggested that material from relatively warmer climates would not respond to cryopreservation as well as material from colder environments. To test this hypothesis, the effect of growing provenance on cryosurvival of dormant buds from three Malus (apple) cultivars grown in three locations (Geneva, NY; Davis, CA; and Corvallis, OR) was tested in 3 consecutive years. Dormant winter buds were harvested at the three locations, cryopreserved, and bud viability was tested by grafting. The collective 3-year mean viability for cryopreserved dormant apple buds for the three locations ranged from 63% to 81% of the buds surviving with the highest survival from the Corvallis site; however, the Geneva twigs were exposed to the lowest preharvest temperature. These results suggest that the temperature at the growing location may not hinder application of the dormant bud cryopreservation method with Malus to the extent previously speculated.