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Mi-Young Chung, Jae-Dong Chung, Jaap Van Tuyl, and Ki-Byung Lim

Intergenomic F1 hybrids between L. auratum and L. henryi were made and backcrossed to Oriental hybrids to produce BC1 progenies. The F1 intergenomic hybrids produced a relevant frequency of 2n-gamete and fertile pollen. Analyses of pollen size, viability, and germination ability were checked under microscopic observation. GISH analysis confirmed that F1 intergenomic hybrids possess a set of chromosomes from both parents and showed an intermediate morphological phenotype. Twenty BC1 plants were generated by in vitro embryo rescue technique, and analyzed for genome composition by GISH. All plants were triploid, showing 12 from female parent (2× Oriental) and 24 from male (2× F1 hybrid). Based on the GISH analyses, 19 BC1 plants were derived from FDR 2n-gamete and only one plant was derived from IMR 2n-gamete of F1 hybrid. The genome composition of 19 BC1 plants from FDR 2n-gamete possess 12 Orientals + 12 L. auratum + 12 L. henryi chromosomes with some extent of homoeologous recombination between L. auratum and L. henryi. However, one plant from IMR 2n-gamete origin contains an odd number of parental chromosomes from F1 hybrid, showing 12 Oriental + 14 L. auratum + 10 L. henryi chromosomes. In this case, two L. auratum chromosomes recombinant with L. henryi chromosome segments were added and L. henryi counterpart chromosomes were deleted, respectively.

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Luping Qu and J.F. Hancock

RAPD markers were used to determine the level of heterozygosity transmitted via 2n gametes from V. darrowi cv. Florida 4b (Fla 4B) to interspecific hybrids with tetraploid V. corymbosum cv. Bluecrop. The tetraploid hybrid US 75 was found to contain 70.6% of Fla 4B's heterozygosity, a value consistent with a first division restitution (FDR) mode of 2n gamete production. Crossovers during 2n gamete formation were evidenced by the absence of 16 dominant alleles of Fla 4B in US 75, and direct tests of segregation in a diploid population involving Fla 4B. RAPD markers that were present in both Fla 4B and US 75 were used to determine the mode of inheritance in a segregating population of US 75 × V. corymbosum cv. Bluetta. More than 30 homozygous pairs of alleles were located that segregated in a 5:1 ratio, indicating US 75 undergoes tetrasomic inheritance.

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Dario J. Chavez and Paul M. Lyrene

reported by Sharpe and Darrow (1959) . V. darrowii clones Fla. 4A and Fla. 4B were used in these foundation crosses ( Sharpe and Sherman, 1971 ). From 1600 pollinations, 31 fertile hybrids were obtained ( Sharpe and Darrow, 1959 ). The 2n gametes in V

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David M. Czarnecki II and Zhanao Deng

normal n (2 x ) gamete formation and fertilization ( Table 2 ), but 5.5% of ‘Gold’ SP progeny and 11.7% of ‘Pink Caprice’ SP progeny were hexaploids ( Table 3 ). The occurrence of these hexaploids indicates that a 2n gamete (4 x ) had been formed

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N. Vorsa and James R. Ballington

Eight highbush blueberry (V. corymbosum L.) triploids (2n = 3x = 36) were crossed with diploids (2n = 2x = 24), tetraploids (2n = 4x = 48), and hexaploids (2n = 6x = 72). No plants were recovered from 4021 3x × 2x crosses. One triploid was relatively fertile in 3x × 4x and 3x × 6x crosses, which is most likely attributable to 2n gamete production in the triploid. The lack of fertility of triploids, which do not produce 2n gametes, in crosses with diploids and tetraploids suggests that the production of gametes with numerically balanced (n = 12 or 24) chromosome numbers is extremely low. In addition, the inability to recover progeny from 3x × 2x crosses also suggests that aneuploid gametophytes and/or zygotes, including trisomics, are inviable in blueberry. Pollen stainability was also highly reduced in triploids. Frequency distributions of anaphase I pole chromosomal constitutions of three triploids were significantly different from one another. Two of the three distributions were shifted toward the basic chromosome number of 12, with one triploid having 25% poles with 12 chromosomes. However, the sterility of 3x × 2x and 2x × 3x crosses indicates that lagging chromosomes during meiotic anaphases are probably not excluded from gametes, resulting in unbalanced gametes in blueberry. Triploids can be used as a bridge to facilitate gene transfer from the diploid and tetraploid levels to the hexaploid level in blueberry.

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Neil O. Anderson and Peter D. Ascher

Male and female fertility, seed germination, and progeny fertility were used to determine cultivar fertility in species of Lythrum. One short-, 11 mid-, and six long-styled cultivars were included in this study. Duplicates of several cultivars from different nurseries and three unknown cultivars from Minnesota gardens were also collected. Plants from 17 Minnesota and one Wisconsin population of L. salicaria served as fertile male and/or female testers. Pollen stainability (usually 100%) showed low levels of male gamete abortion. Pollen size within and among anther type varied widely; possible 2n gametes were present in primarily the short- and mid-anther morphs. Seed production per capsule from legitimate cross-pollinations, using cultivars as male parents with Minnesota or Wisconsin female testers, averaged 48 ± 36 across style morphs. Cultivars differed as males, as did anther morphs. With female fertility tests, seed set per capsule ranged from zero to 152 and averaged 54 ± 40 in legitimate pollinations (i.e., pollinations between stamen and styles of the same length). Seed set for other crosses showed similar trends. Only `Morden Gleam' produced no seed with all legitimate pollinations, although illegitimate selfs or interspecific crosses produced seed. Seed from legitimate crosses of L. salicaria × cultivars had 30% to 100% germination. Common male and female parents within each legitimate crossing group were not significantly different. This study showed that the cultivars are highly fertile when used as male or female parents with wild purple loosestrife, native species (L. alatum Pursh.), or other cultivars. Thus, cultivars grown in gardens could serve as pollen or seed sources for the continued spread of purple loosestrife. The implications of cultivar fertility, especially interspecific F1 hybrids, is discussed in relation to the spread of noxious weeds in wetlands.

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Xuhong Zhou, Xijun Mo, Yalian Jiang, Hao Zhang, Rongpei Yu, Lihua Wang, Jihua Wang, and Suping Qu

number of the mother cell. Thus, to generate haploid spores, a meiocyte must enter M I after prophase, pass through the M I to M II transition, and complete M II. Errors in transitions are not uncommon and may lead to the production of viable, 2n gametes

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Kathleen G. Haynes, Beverly A. Clevidence, David Rao, and Bryan T. Vinyard

interactions is currently unknown in potatoes. Commercial potatoes are tetraploid, whereas the high-carotenoid clones identified to date have been diploid ( Brown et al., 1993 ; Lu et al., 2001 ). Ploidy levels can be manipulated through the use of 2n gametes

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Dario J. Chavez and Paul M. Lyrene

produce 2n gametes. It was originally thought that crossing V. darrowii (2x) with northern highbush blueberry cultivars [ V. corymbosum (4x)] would produce sterile triploid progeny ( Sharpe and Darrow, 1959 ). Instead, Sharpe and Darrow obtained 31

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David M. Czarnecki II and Zhanao Deng

Lantana camara is an important plant for the environmental horticultural industry, yet it can be invasive, cross-pollinating with native lantana and dispersing fruit (and seeds) to natural and agricultural lands. Identification and development of sterile cultivars is much needed to meet industry and consumer needs for noninvasive plant materials. Previously we evaluated the male fertility of 32 L. camara cultivars/breeding lines at five ploidy levels. This study was to assess their female fertility and understand the relationship between female fertility and ploidy level and the production of unreduced female gametes (UFGs) in L. camara. These cultivars/breeding lines significantly varied in percent fruiting plants (6.3% to 100.0%), percent fruiting peduncles (0.3% to 98.8%), fruit per peduncle (0.003 to 7.173), seed germination (0% to 57.1%), and female fertility index (0.003 to 2.998). Certain diploids (e.g., ‘Denholm White’) were highly female-sterile. Eleven of the 13 triploids evaluated were UFG-producing and rather fertile. The two non-UFG-producing triploids had the female fertility index of 0.005, thus most sterile. Tetraploids, especially those producing UFGs, were prolific fruit producers. These results show that ploidy level and UFG production play a significant role in determining fruit (seed) production capacity and female fertility of L. camara. None of the commercial triploid cultivars evaluated reached desirable levels of male and female sterility, indicating a strong need to develop new lantana cultivars that are male- and female-sterile. Our results suggest that production and selection of triploids can be effective to sterilize L. camara, but it is imperative to select diploids and tetraploids that do not produce UFGs as the breeding parents.