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  • Author or Editor: C. Thomas Chao x
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Compatibilities among mandarin cultivars raise concern, especially related to the seediness issue in mandarin production. A hand cross-pollination study was conducted in 2002 and 2003 at the UC Lind-cove Research and Extension Center, Exeter, California. There were 0.86% (1/116) (4 seeds) and 0% (0/137) fruit set from `Fina Sodea' Clementine × `Tahoe Gold' mandarin in 2002 and 2003, respectively. There were 13.59% (14/103) (average 1.5 seeds/fruit) and 16.50% (17/103) (average 9.82 seeds/fruit) fruit set from `Nules' Clementine × `Tahoe Gold' mandarin (a triploid) in 2002 and 2003, respectively. There were 30.84% (33/107) (average 23.42 seeds/fruit) and 0% (0/110) fruit set from `Fina Sodea' Clementine × `Afourer' mandarin in 2002 and 2003, respectively. There were 39.62% (42/106) (average 25.36 seeds/fruit) and 4.92% (3/61) (average 31.66 seeds/fruit) fruit set from `Nules' Clementine × `Afourer' mandarin in 2002 and 2003, respectively. There was 28.32% (32/113) (average 12 seeds/fruit) from `Afourer' mandarin × `Fina Sodea' Clementine in 2002. There was 28.04% (30/107) (average 9.47 seeds/fruit) from `Afourer' mandarin × `Nules' Clementine in 2002. These results showed pollen of `Afourer' mandarin can cause large number of seed in both Clementine cultivars. The pollen from the triploid `Tahoe Gold' mandarin can set fruit and cause seeds in diploid `Nules' Clementine but not in diploid `Fina Sodea' Clementine. These results imply that proper buffer distance is needed between Clementines and `Afourer' mandarin in order to produce seedless mandarins in California.

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Acreages of `Nules' Clementine and `Afourer' mandarin have increased rapidly in California. One way to produce seedless mandarins is using Navel oranges or Satsuma mandarins as buffer to prevent cross-pollination. In order to determine the number of necessary buffer rows or spacing to prevent cross-pollination, we used AFLP markers to determine the pollen parentages of `Nules' and `Afourer' seedlings from two sites. The AFLP markers were able to identify Clementine as pollen parents of 26.6% (25/94) of the `Afourer' seedlings from one site. The pollen of Clementine was able to travel across minimum of 32 rows to pollinate `Afourer' mandarins. We found 12.73% (14/110) of the `Afourer' seedlings at the east side of the site were progenies of `Minneola' tangelo. Pollen of `Minneola' was able to travel across minimum 94 rows to pollinate `Afourer' mandarins. 12.73% (14/110) of the `Afourer' seedlings at the east end of the site were progenies of Clementine. Pollen of Clementine was able to travel minimum 54 rows to pollinate the `Afourer' mandarin at the east end of the site. The AFLP markers also identified `Afourer' mandarin as pollen parents of almost all `Nules' seedlings (98.63%, 72/73) at a second site. The pollen of `Afourer' was able to travel across minimum of 74 acres of empty ground from the east or minimum of 91 rows of Navel (128 acres) from the north to pollinate `Nules' Clementine. The results showed how far can compatible pollens traveled to cause seeds in mandarins in California. The implication from the results in seedless mandarin production in California is discussed.

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Calathea, the largest genus in the family Marantaceae, is composed of 100 species native to tropical America in moist or swampy forest habitats. Because of their brilliant patterns of leaf color and different textures plus ability to tolerate low light levels, calatheas have been widely produced as ornamental foliage plants for interiorscaping. Thus far, genetic relationships among its species and cultivars have not been documented. This study analyzed the relationships of 34 cultivars across 14 species using amplified fragment length polymorphism (AFLP) markers. Six EcoR I + 2/Mse I + 3 primer set combinations were used in this investigation. Each selected primer set generated 105 to 136 scorable fragments. A total of 733 AFLP fragments were detected of which 497 were polymorphic (68%). A dendrogram was constructed using the unweighted pair-group method of arithmetic averages (UP-GMA) technique and a principal coordinated analysis (PCOA) was used to analyze the relationships. The 34 cultivars were divided into four clusters. Cluster I had 19 cultivars derived from C. roseo-picta and C. loesnerii with Jaccard's similarity coefficients from 0.74 to 0.97, of which six are somaclonal variants or sports and two cultivars are genetic identical. Only C. kennedeae `Helen' is positioned in cluster II. Cluster III had 10 cultivars across seven species; Jaccard's similarity coefficients among them varied from 0.41 to 0.63. Four species were situated in cluster IV with Jaccard's similarity between 0.27 to 0.41. Results from this study indicate that broadening of genetic diversity is needed for cultivars in cluster I as they are the most commonly grown calatheas but genetically are very close.

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Anthurium is the largest genus in the family Araceae, consisting of about 1000 species. Anthuriums are valued for their colorful spathes and traditionally used as cut flowers. With the introduction of compact cultivars through breeding, a series of container-grown cultivars have been released and widely produced as flowering foliage plants. However, limited information is available about genetic relatedness among these container-grown cultivars. This study analyzed genetic relationships of 58 cultivars using amplified fragment length polymorphism (AFLP) markers with near infrared fluorescence labeled primers. Forty-eight EcoR I + 2/Mse I + 3 primer set combinations were screened from which six primer sets were selected and used in this investigation. Each selected primer set generated 94 to 115 scorable fragments. A total of 647 AFLP fragments were detected of which 401 were polymorphic (67%). All cultivars were clearly differentiated by their AFLP finger-prints. A dendrogram was constructed using the unweighted pair-group method of arithmetic averages (UPGMA) technique and a principal coordinated analysis (PCA) was used to analyze the relationships. The 58 cultivars were divided into three clusters; clusters I, II, and III had 40, 10, and 8 cultivars, respectively. Most commonly grown cultivars were positioned in cluster I, where had Jaccard similarity coefficients among them ranged from 0.7 to 0.98. Eighteen of the 40 shared Jaccard similarity coefficient of 0.8 or higher, indicating that genetic diversity for cultivated container-grown Anthurium is needed.

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There are several Central Asian Malus species and varieties in the USDA-ARS National Plant Germplasm System (NPGS) apple collection. Malus sieversii is the most comprehensively collected species native to Central Asia. Other taxa such as M. sieversii var. kirghisorum, M. sieversii var. turkmenorum, M. pumila, and M. pumila var. niedzwetzkyana have primarily been donated to the collection by other institutions and arboreta. We sought to determine if genetic and/or phenotypic differences among the individuals that make up the gene pools of these taxa in the NPGS exhibit unique characteristics. Genetic data, based on microsatellite analyses, suggested that the diversity within each taxa is significantly greater than that among taxa. Trait data also revealed very few differences among taxa, the primary characteristic being the dark red fruit coloration and tinted flesh color of the accessions assigned to M. pumila var. niedzwetzkyana resulting from a known single-gene mutation in anthocyanin production. We found that M. sieversii is a highly diverse species with a range in genetic and phenotypic trait variation that includes the characteristics of the other Central Asian taxa of interest. We conclude that the gene pools that comprise the accessions within the NPGS Central Asian Malus collection are highly overlapping with respect to both phenotypic traits and genotypic characters.

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The U.S. Department of Agriculture, Agricultural Research Service, National Plant Germplasm System (NPGS), Plant Genetic Resources Unit apple (Malus) collection in Geneva, NY, conserves over 2500 trees as grafted clones. We have compared the genotypes of 1131 diploid Malus ×domestica cultivars with a total of 1910 wild and domesticated samples representing 41 taxonomic designations in the NPGS collection to identify those that are genetically identical based on nine simple sequence repeat (SSR) loci. We calculated the probability of identity for samples in the data set based on allelic diversity and, where possible, use fruit images to qualitatively confirm similarities. A total of 237 alleles were amplified and the nine SSRs were deemed adequate to assess duplication within the collection with the caveat that “sport families” likely would not be differentiated. A total of 238 M. ×domestica and 10 samples of other taxonomic groups shared a genotype with at least one other M. ×domestica individual. In several cases, genotypes for cultivars matched genotypes of known rootstocks and indicated that these accessions may not accurately represent the indicated named clones. Sets of individuals with identical genotypes and similar cultivar names were assigned to sport families. These 23 sport families, comprised of 104 individuals, may have mutational differences that were not identified using the nine SSR loci. Five of the selected markers (CH01h01, CH02d08, CH01f02, G12, GD147) overlap with sets of markers that have been used to fingerprint European apple collections, thus making it possible to compare and coordinate collection inventories on a worldwide scale.

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The USDA-ARS National Plant Germplasm System Malus collection is maintained by the Plant Genetic Resources Unit (PGRU) in Geneva, NY. In the 1990s, a core subset of 258 trees was hand-selected to be representative of the grafted Malus collection. We used a combination of genotypic and phenotypic data to compare the diversity of the 198 diploid trees in the original core subset with that of 2114 diploid trees in the grafted field collection for which data were available. The 198 trees capture 192 of the 232 total microsatellite alleles and have 78 of the 95 phenotypic characters. An addition of 67 specific individuals increases the coverage to 100% of the allelic and phenotypic character states. Several de novo core sets that capture all the allelic and phenotypic character states in 100 individuals are also provided. Use of these proposed sets of individuals will help ensure that a broad range of Malus diversity is included in evaluations that use the core subset of grafted trees in the PGRU collection.

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