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David M. Czarnecki II, Amanda J. Hershberger, Carol D. Robacker, David G. Clark and Zhanao Deng

stainability (11.9% to 21.2%). Meiotic abnormalities. Five cultivars, Lola (diploid with high pollen stainability), Pink Caprice (tetraploid with high pollen stainability), Miss Muffet and New Gold (triploids with extremely low pollen stainability), and Athens

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Yan Ma, Charles F. Crane and David H. Byrne

The tetraploid (2n = 4x = 28) rose 86-7 (Rosa wichuraiana × R. rugosa rubra) and its hybrids with the thornless tetraploid rose cultivar Basye's Blueberry (2n = 28) were analyzed for meiotic configuration frequencies and meiotic abnormalities. Genomic relationships in these hybrids were interpreted with the aid of a model of meiotic chromosome association in tetraploids. The closest-fitting model solutions indicated a 2:2 (AABB) pattern of genomic relationships, with 65% to 90% of all association between most closely related genomes. Some of the optimal solutions were transitional to a “ring4” pattern, in which one of the possible pairing arrangements is suppressed. The same configuration frequencies could also reflect a “4:0” pattern of equally similar genomes with fractionally more than two independent pairing and chiasma-forming domains per chromosome. Observed meiotic abnormalities included chromosome stickiness and asynchronous chromosome contraction within cells. Pollen stainability varied independently of meiotic irregularity or multivalent frequency. The observed configuration frequencies are consistent with partially tetrasomic inheritance that retains considerable heterozygosity, but allows individual contributions from parental genomes to become homozygous.

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David M. Czarnecki II and Zhanao Deng

doubling or gametic nonreduction ( Bretagnolle and Thompson, 1995 ). The former results from mitotic abnormalities in somatic (zygotic and meristematic) cells, while the latter results from meiotic abnormalities during gamete or gametophyte genesis and the

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Dario J. Chavez and Paul M. Lyrene

tetrads as seen under the microscope. Meiotic abnormalities during pollen formation probably produced the many abnormal tetrads (unstained sporads) and the 2n pollen sporads. FL07–110-F 1 was probably triploid because of the reduced pollen fertility and

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Ryan N. Contreras, Thomas G. Ranney and Shyamalrau P. Tallury

sterility, is often the result of improper chromosome pairing during gametogenesis resulting from structural differences in parental chromosomes. This results in meiotic abnormalities such as univalents and lagging chromosomes; however, other mechanisms may

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Zhiyong Hu, Min Zhang, Qigen Wen, Jie Wei, Hualin Yi, Xiuxin Deng and Xianghua Xu

types until the formation of MMCs. In the mutant, monads and polyads with various numbers and sizes of microspores were formed at the tetrad stage, suggesting meiotic abnormality in MMCs. Chen et al. (2004) also observed similar phenomena in citrus

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Hirotoshi Tsuda, Hisato Kunitake, Mai Yamasaki, Haruki Komatsu and Katsunori Yoshioka

) hybrids averaged only 0.9%. Low pollen fertility of these intersectional hybrids was the result of the infrequency of normal bivalent pairing between the two chromosome sets and numerous meiotic abnormalities from chromosome structural differentiation

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Jason D. Lattier and Ryan N. Contreras

, it remains unclear if meiotic abnormalities in gamete formation, preferential fertilization, or preferential embryo/endosperm survival skewed the distribution of aneuploid cytotypes. Our results may simply be due to the small sampling population of

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Kelly J. Vining, Ryan N. Contreras, Martin Ranik and Steven H. Strauss

structural differences in parental chromosomes, which result in improper chromosome pairing during gametogenesis. Sterility resulting from meiotic abnormalities is often referred to as hybrid sterility or chromosomal hybrid sterility and represents an