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Christopher S. Cramer

Determination of ploidy is an essential plant breeding technique. Laboratory exercises for teaching students how to determine ploidy in plant tissues using various techniques are described for geranium and onion. The different methods include root tip squashes, pollen mother cell squashes, pollen grain size and germinal pore counts, stomata size and density determination, and gross morphology.

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Pablo Bolaños-Villegas, Shih-Wen Chin, and Fure-Chyi Chen

camera (E4500; Nikon). Sporad quantification in pollen mother cells (PMCs). To quantify the frequency of different types of sporads in hybrids, PMCs were stained with lactophenol-acid fuchsin solution ( Lim et al., 2001 ). Pollinia from full

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T. K. Toyama

Abstract

Twenty-four haploids of peach [Prunus persica (L.) Batsch] were obtained by visual selection in seedling populations growing in the greenhouse. Frequencies varied markedly between some progenies. Meiosis in pollen-mother cells was extremely irregular. Ten haploids diploidized by colchicine treatment were fertile and resembled natural diploids.

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Kenichiro Kaneko and Haruyuki Kamemoto

Abstract

The chromosome number was 2n = 30 for Anthurium andreanum Linden ‘Kaumana’ and 2n = 30 +2B for ‘Uniwai’. The karyotypes, in addition to the 2 B chromosomes in ‘Uniwai’, consisted of 4 large metacentric, 2 fairly large satellite and 24 smaller chromosomes. Meiotic configurations in pollen mother cells were similar for both cultivars with the exception of 2 B chromosomes in ‘Uniwai’. Meiotic irregularities suggest a hybrid origin of cultivated anthuriums.

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E. E. Umanah and R. W. Hartmann

Abstract

The chromosome numbers of both Manihot esculenta Crantz and M. glaziovii Muell.–Arg. were found to be 2n = 36. The karyotypes of the two species are similar. Two pairs of satellited chromosomes are reported for the first time for both species. Meiosis was normal in pollen mother cells; the 18 bivalents at MI disjoined regularly at AI. We suggest that these Manihot species are allopolypoids with a basic chromosome number of x = 9.

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K. R. McCammon and S. Honma

Abstract

Interspecific hybrids between Solanum melongena L. cv. Millionaire and S. torvum Sw. were produced by hybridization using S. torvum as the pollen parent. The progeny was determined to be hybrid based on morphological and cytological observations. Reciprocal attempts to self- and backcross the hybrid to the parental species were unsuccessful. Observations of the pollen from the F1 plants indicated low viability. Meiosis in the parents appeared normal. Cytological observations of hybrid pollen mother cells (PMC) indicated abnormalities at all meiotic stages.

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Toru Arisumi, Joseph Uhring, and Robert L. Pryor

Abstract

Rhododendron sp. cv. Roseum Elegans initiated floral buds from June 1–14 in Beltsville, Maryland. Perianth parts and stamens were initiated by June 14 and carpels by August 9. The ovary was formed by August 23, and ovules were initiated by September 6. Differentiation of stamens was complete by August 23; depending on the season, pollen mother cell (PMC) divisions began as early as August 24 or as late as September 24. Megasporogenesis leading to the formation of 8-nucleate embryo sacs occurred from April 25–May 2, about 1 or 2 weeks before full bloom.

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R. L. Lower and K. W. Johnson

Abstract

Autotetraploid watermelons were produced by treating the growing points of diploid seedlings with aqueous colchicine solution or by soaking diploid seeds in colchicine solution. The soaking method was more effective.

Diploid pollen was apparently more viable than tetra-ploid pollen. Examination of germinating tetraploid pollen revealed that while over two-thirds germinated normally a small percentage sent forth 2, 3 or 4 normalsized pollen tubes or a single bifurcated tube. Germinating diploid pollen always put forth only one unbranched pollen tube. Tetraploid plants did not set fruit when pollinated with pollen from tetraploids; however, they did set fruit when pollinated with pollen from diploids.

Cytological observations were made of pollen mother cells of both diploid and tetraploid plants. Meiosis in diploids was regular; however, irregularities were observed in tetraploids. Examination of some pollen mother cells of tetraploids at the quartette stage revealed micro sporocytes in addition to the 4 microspores. The abnormal quartette formations and lower pollen viability of tetraploids were believed associated with irregularities observed at meiosis. Preliminary investigations of megaspore formation revealed no apparent differences between the diploid and tetraploid megaspores. Although meiotic irregularities were found, a sufficient amount of apparently viable pollen was observed. A physiological basis for the self-sterility is suggested.

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Chang-Yeon Yu and John Masiunas

The objective of this study was to investigate the chromosomal and genotypic variation in regenerated plants of Solarium and Lycopersicon. Calli of Lycopersicon peruvianum genotypes PI199380, PI126345, PI251301, and LA1373, along with Solanum ptycanthum were transferred onto media consisting of MS salts with Gamborg vitamins. The shoots formed were rooted in vitro and transferred to greenhouse soil. Actively growing root tips were harvested and pretreated, fixed, hydrolyses and stained. Pollen mother cells were fixed in propionic alcohol solution and stained with aceto-carmine. The number of chromosomes were counted. The greatest variation was in Solanum ptycanthum with chromosome numbers ranging from 18 to 60 (2n=24). Progeny analysis for 12 somaclones of Solarium ptycanthum was done by selfing for two generations. Morphology, shoot height, and weight were determined in each generation. The amount of variation differed among the somaclonal lines.

Open access

Frank S. Santamour Jr.

Abstract

Hybrids between diploid (2n = 28 chromosomes) elm (Ulmus) species that normally flower in March or April and those that normally flower in August or September flowered at various times from late October to mid-November when grown in Washington, D.C. Although such hybrids did not produce viable seed, they did produce apparently sound pollen. Chromosome pairing at diakinesis in pollen mother-cells in most of the diploid hybrids was sufficiently complete to allow normal meiosis to take place. An aneuploid (2n = 39) three-species hybrid with a preponderance of chromosomes from spring-flowering species produced abnormal flower buds in which meiosis took place later in the spring than American elm, but did not undergo anthesis.