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normal sexual reproduction, genetic uniformity and hybrid vigor are lost after the F1 generation, but with apomixis these traits can be maintained through many generations due to a fixed heterozygosity ( Koltunow et al., 1995 ; Ortiz et al., 2013

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Apomixis, i.e., asexual reproduction through seeds, is a natural trait of reproduction in plants ( Ozias-Akins, 2006 ). Unlike sexual seed formation, it does not involve the formation of normal female gametes or fertilization; however, it does

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fragmentation can lead to reproductive failure and even further losses ( Wetzstein and Yi, 2010 ). Genetic diversity tends to be reduced in small, isolated populations to the point where sexual reproduction may not be possible ( Ellstrand and Elam, 1993 ) in

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plants required for the production of liquor, it is necessary to establish measures to promote the spread and protection of populations. Slow growth, low rate of asexual reproduction, and sexual reproduction limited by problems of pollination and seed

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( Liang et al., 2005 ). This study investigated the processes of microsporogenesis and megasporogenesis and the development of male and female gametophytes. Our goal was to elucidate whether reproductive disorders exist in the sexual reproduction of

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The tangerine-virescent (tv) mutation was reported as a single gene somaclonal variant from tissue culture (Evans and Sharp 1963). A replicated field trial was conducted to characterize variation and stability in the phenotype of this tv somaclone and to compare it with the inbred parent from which it was reportedly derived.

Heritability and stability of the tv somaclonal variant was measured by comparing R3 end R4 lines of sexual progenies of the original tv variant and with its sexually derived inbred parent UC82B. Several additional variants were observed in these tv lines, including fruit shape, days to first flower, fruit weight, yield, plant type, and fertility. Eight sterile or semi-sterile plants were discovered in 6 of 39 R4 lines. Our results suggest that multiple genetic changes have occurred in the tv somaclonal variant and while the original tv mutant is stably inherited, additional genetic abnormalities occur following sexual reproduction.

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Guayule (Parthenium argentatum Gray) has been difficult to improve through classical plant breeding because of its facultative apomictic reproductive system. Attempts have been made to increase rubber concentration and yield by examining traits correlated with rubber production and their heritabilities. We propose a new way of estimating heritability in guayule that more accurately accounts for the contributions of apomictic and sexual reproduction. At two years of growth, there was a significant relationship between the parents and the progeny for all traits measured, except for rubber and guayulin B concentrations. Due to the facultative apomictic nature of guayule reproduction, heritabilities are more accurately presented as a range of values between the narrow and broad sense heritabilities. Since guayule is more apomictic than sexual, most heritabilities will be closer to the broad sense values. To increase resin and rubber yield in the progeny, selection should focus on height and width in the parents because height and width are highly correlated with rubber yield, with the highest heritabilities (0.65 to 1.00 and 0.97 to 1.0, respectively) of the traits measured.

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Apomixis is asexual reproduction through seed. Apomixis in the genus Pennisetum is of the gametophytic (aposporous) type. Genes for apomixis have been transferred from a wild apomictic species (P. squamulatum) to pearl millet (P. glaucum) by conventional breeding to produce an obligately apomictic backcross 3 (BC3) plant (Dujardin and Hanna, 1989, J. Genet. Breed. 43:145). Molecular markers based on restriction fragment length polymorphisms and random amplified polymorphic DNAs were identified in BC3 that were shared only with the apomictic parent. Segregation of these informative markers in a BC4 population indicated that three linkage groups from P. squamulatum were present in BC3 and that minimal recombination between these alien chromosomes and those of the recurrent parent occurred. Transmission of only one of the linkage groups was required for transfer of apomixis. Recombination is essential for genetic mapping, thus we are beginning to map the informative molecular markers in an F, interspecific cross between pearl millet and P. squamulatum, a population that segregates for apomictic and sexual reproduction.

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Starfruit (Averrhoa carambola L.) is reproduced by seeds from `Criollo' cultivars. The replication of desirable agronomic traits is difficult when selected plants are from sexual reproduction. The heterogeneity of plants is observed as higher trees, irregular fresh fruit yield, variable fruit quality, differential insect pest and disease susceptibilities, and extended period for recovering the inversion. Vegetative propagation is an alternative for reducing the heterogeneity of starfruit trees. Four grafting methods for propagating starfruit in the coast of Colima, Mexico: splice-side graft, wedge graft, whip graft, and bud graft were evaluated. The experiment was carried out on the Tecoman campus of the Universidad de Colima. The ambient conditions were dry tropic (BS1). Seven-month-old rootstocks were obtained from Criollo seedlings, and the scion was obtained from a healthy 15-year-old `Miss' donor tree. The experiment was distributed under a completely randomized design. The splice-side graft had 70% success and was the best, bud graft had 40% success, wedge graft, had 5% success and whip graft 0% success, and was the least successful.

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Floral initiation signals the commencement of sexual reproduction in angiosperms. In many plant species this developmental phase is controlled by photoperiod. However, it may be regulated by other factors, such as plant age or specific temperature or irradiance requirements. Floral initiation occurs in Pelargonium ×domesticum (regal Pelargoniums) in response to exposure to cool (7–12°C) temperatures for about 4–6 weeks, or to cumulative irradiance at 18–23°C. Broad genetic variability exists so that floral initiation in some cultivars is almost completely controlled by temperature, while in others it is almost completely controlled by cumulative irradiance. Among the latter group of genotypes, genetic variability exists for the amount of irradiance required. The purpose of this study was to determine the precise irradiance requirements for nine commercially important cultivars. The cultivars varied significantly in their response to irradiance with respect to floral initiation. Low irradiance requiring genotypes developed visible (5 mm) buds with as little as 250 mol of total cumulative irradiance; floral initiation in these cultivars occurred with only 50 mol of irradiance. High irradiance requiring genotypes still had vegetative meristems after 300 mol of total cumulative irradiance. Further studies were conducted on `Majestic', chosen for its high irradiance requirement. The objective of this study was to determine whether cool temperatures (7–12°C) or heat stress (23–28°C) could replace the irradiance effect. The results indicated that neither of these environmental conditions could replace the effects of moderate temperature (18–23°C) and high cumulative irradiance in this cultivar.

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