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Mohammad Sadat Hosseini Grouh, Kourosh Vahdati, Mahmoud Lotfi, Darab Hassani, and Nejat Pirvali Biranvand

Virmani, 1996 ). Several methods have been tested for induction of haploids, including anther and microspore culture and in situ parthenogenesis by irradiated pollen followed by in vitro culture of immature embryos in fruit trees ( Germana, 2006 ). Haploid

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Kristina Košmrlj, Jana Murovec, and Borut Bohanec

significantly reduced. In 2011, most accessions tested as female parents responded positively to haploid induction by induced parthenogenesis, whereas in 2012, haploid induction rates were generally lower. A comparison is given in the case of ‘Gleisdorfer

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Elisabet Claveria, Jordi Garcia-Mas, and Ramon Dolcet-Sanjuan

Homozygous doubled haploid lines (DHLs) from new cucumber (Cucumis sativus L.) accessions could be useful to accelerate breeding for resistant varieties. DHLs have been generated by in vitro rescue of in vivo induced parthenogenic embryos. The protocol developed involves the following: 1) induction of parthenogenic embryos by pollinating with pollen irradiated with a Co60 γ-ray source at 500 Gy; 2) in vitro rescue of putative parthenogenic embryos identified by their morphology and localized using a dissecting scope or X-ray radiography; 3) discrimination of undesirable zygotic individuals from the homozygous plants using cucumber and melon SSR markers; 4) determination of ploidy level from homozygous plants by flow cytometry; 5) in vitro chromosome doubling of haploids; and 6) acclimation and selfing of selected lines. Codominant markers and flow cytometry confirmed the gametophytic origin of plants regenerated by parthenogenesis, since all homozygous lines were haploids. No spontaneous doubled haploid plants were rescued. Chromosome doubling of haploid plants was accomplished by an in vitro treatment with 500 μm colchicine. Rescue of diploid or chimeric plants was shown by flow cytometry, prior to their acclimation and planting in the greenhouse. Selfing of colchicine-treated haploid plants allowed for the perpetuation by seed of homozygous lines. The high rate of seed set, 90% of the lines produced seed, facilitated the recovery of inbred lines. Despite some limiting factors, parthenogenesis is routinely used in a cucumber-breeding program to achieve complete homozygosity in one generation. Breeding for new commercial hybrid cultivars will be accelerated. DHLs are ideal resources for genomic analyses.

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Maria Jose Gonzalo, Elisabet Claveria, Antonio J. Monforte, and Ramon Dolcet-Sanjuan

isolated microspores (androgenesis), ovules (gynogenesis), or in vitro rescue of parthenogenic embryos induced in situ through pollination with irradiated pollen (parthenogenesis). In Cucurbitaceae species, haploid plants have been obtained by gynogenesis

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Ramon Dolcet-Sanjuan, Elisabet Clavería, Alfonso J. Rodríguez, and Marta Llaurado

Callus and shoot organogenesis were obtained from anthers of Dianthus caryophyllus L. `Manon', `Amapola', `Elsy', and `IB212', harboring mid-uninucleated microspores. Significant differences between genotypes were observed on number of responsive anthers (10.4% to 72.1%) and rescued plants per responsive anthers (1.2% to 4.8%). A modified H medium (Nitsch and Nitsch, 1969) with 20 g/L maltose and 0.25% Gelrite, supplemented with 10 μM 2,4-D and 1 μM TDZ, was most appropriate for callus induction. Plants were regenerated after subsequent subculture to the same medium, but amended with 0.1 μM TDZ. Zymogram types for aminopeptidase (AAP) in polyacrilamide gel electrophoresis proved that all 40 plants regenerated from `Amapola', `Elsy', or `IB212' where heterozygous, and consequently not originated from the microspores but from somatic tissue. Alternatively, in situ-induced parthenogenesis through pollination with gamma-irradiated pollen and in vitro embryo rescue was tested. A total of 92 embryos, including normal and no cotyledonary embryos, were rescued from 38 fruits harvested out of 70 crosses between `Scania' and `Amapola'. Embryos were rescued 21 to 28 days after pollination by culture in a modified E20A (Sauton and Vaulx, 1987) medium. Phosphogluco isomerase (PGI) and Shikimic dehydrogenase (SDH) zymograms in starch gel electrophoresis, and AAP in polyacrilamide gel electrophoresis, indicated the parthenogenic origin of three of the regenerated plants. Flow cytometry of nuclei proved the early diploidization, during in-vitro micropropagation, of the parthenogenic carnation haploid plantlets.

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Stephen L. Krebs

Genus Rhododendron contains more than 800 species worldwide, currently grouped into eight subgenera. Four of these subgenera—comprising the evergreen azaleas, deciduous azaleas, small scaly-leaved rhododendrons, and large non-scaly leaved rhododendrons—have been the focus of ornamental breeding for over 150 years. As a rule of thumb, species within a subgenus are cross-fertile, and most hybrids are derived from intra-subgeneric crosses. Success with wider (inter-subgeneric) crosses, especially deciduous azaleas × large-leaved rhododendrons, has been occasionally reported in the past, based on the intermediate morphology of the hybrids. I crossed a tetraploid `Ilam group' azalea with R.`Catlalgla' (a selection of the native diploid rhododendron species R. catawbiense) and produced a small population of seedlings that proved to be true `azaleodendron' hybrids, based on shared parental alleles at 2 isozyme loci, Idh-1 and Mdh-3. However, none of the progeny are hybrid in appearance; they share the leaf morphology and deciduous trait of the maternal azalea parent. I attribute this result to a dosage effect in these (probable) triploid hybrids, where the azalea genetic contribution is twice that of the rhododendron parent. Higher copy number can be inferred from stronger band intensities for the azalea gene at diallelic loci (Idh-1), or from triallelic loci (Mdh-3) where the genetic contribution to the hybrid progeny appears to be 2:1, azalea: rhododendron. Previously, azalea-like progeny from azalea × rhododendron crosses were thought to result from parthenogenesis or accidental self-pollination.

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D. Esmenjaud, J.C. Minot, R. Voisin, J. Pinochet, and G. Salesses

Resistance variability was evaluated for five rootstock: three Myrobalan plum (Prunus cerasifera Ehr.) genotypes (P.1079, P.2175, and P.2032) grown from in vitro plantlets, one peach (P. persica (L.) Batsch `GF 305') grown from seeds, and one peach-almond hybrid (P. persica × P. amygdalus Batsch `GF 557') grown from rooted cuttings. Twenty-two root-knot nematode populations from different origins were used: Meloidogyne arenaria (Neal) Chitwood (six populations), M. incognita (Kofoid and White) Chitwood (eight populations), M.javanica (Treub) (four populations), M. hispanica Hirschmann (one population), M. hapla Chitwood (two populations), and an unclassified root-knot species (one population). The study was conducted under greenhouse conditions for 1 and 2 months. No galling or nematode reproduction was observed in P.1079 and P.2175, which should be considered immune; P.2032 showed the highest galling and nematode counts when inoculated with M. hispanica and M. javanica. In P.2032, a high proportion of males was recovered in populations that had a limited development. Because the populations of the first four Meloidogyne species reproduce by obligatory mitotic parthenogenesis, high sex ratio maybe the expression of a late form of resistance. Host suitability of `GF 305' was highly variable among M. arenaria and M. incognita populations. A lower relative variation was observed in M. javanica. `GF 557' was resistant to M. arenaria and M. incognita except for one population of M. arenaria that was weakly aggressive and susceptible to M. javanica. Consequently, resistances specific to the genus Meloidogyne for the Myrobalan plum genotypes P.1079 and P.2175, specific to the nematode species for `GF 557', and specific to the nematode population for `GF 305', were evidenced. This study indicates that, in rootstock selection procedures, it is important to test resistance to several populations within the same nematode species.

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Fenfen Yan, Zhiguo Liu, Mengjun Liu, Xingjuan Zheng, Zhi Luo, and Jiurui Wang

determined by the pollen germination method ( Zhang, 1990 ). Identification of parthenocarpy and parthenogenesis of male-sterile germplasm. The trees that possessed the male-sterile trait were covered under a nylon net before flowering, excluding other jujube

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Hatsuhiko Okada, Yoshitaka Ohashi, Mamoru Sato, Hideyuki Matsuno, Toshiya Yamamoto, Hoytaek Kim, Tatsuro Tukuni, and Sadao Komori

, the first approaches were conducted to produce doubled haploids in apple by in vitro anther culture ( Nakayama et al., 1972 ). Since then, various homozygous genotypes induction methods such as in vitro anther culture and in situ parthenogenesis in

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Milorad Vujičić, Aneta Sabovljević, Jasmina Šinžar-Sekulić, Marijana Skorić, and Marko Sabovljević

micropropagation and long-term conservation of the endangered moss Splachnum ampullaceum Biol. Plant. 50 339 345 Lal, M. 1984 The culture of bryophytes including apogamy, apospory, parthenogenesis and protoplasts 97 115 Dyer A.F. Duckett J.G. The experimental