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Chandra Thammina, Mingyang He, Litang Lu, Kaishuang Cao, Hao Yu, Yongqin Chen, Liangtao Tian, Junmei Chen, Richard McAvoy, Donna Ellis, Degang Zhao, Yuejin Wang, Xian Zhang, and Yi Li

. Determination of ploidy. Flow cytometry was used to determine the ploidy level of the endosperm-derived E. alatus ‘Compactus’ plants. Ploidy determination was based on the total DNA content per nucleus measured with a CyFlow Ploidy Analyser (Partec GmbH

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Sandra M. Reed, Keri D. Jones, and Timothy A. Rinehart

was measured for each nucleus using a Partec PA-1 ploidy analyzer (Partec GmbH). For each sample, at least 5000 nuclei were analyzed, revealing a single peak with a cv <5.0% for all but two samples. Twelve samples were processed twice, and data were

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S. Brooks Parrish and Zhanao Deng

value of this new ploidy level and this new chromosome number, UF-15-414 and its known parents and grandparents, and ‘White Wing’ and two of its known progeny cultivars were characterized at the individual, cellular, and molecular levels. Specifically

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H.O. Oselebe, A. Tenkouano, M. Pillay, I.U. Obi, and M.I. Uguru

The majority of edible bananas (Musa L.) are triploid (2n = 3x = 33) cultivars known as dessert, plantain, or cooking bananas with predominant AAA, AAB, and ABB genomes, justifying the aim of breeding programs to develop improved hybrids of the different utilization classes in the triploid background. This usually involves crossing 3x landraces to 2x accessions that are donors of resistance genes, selecting 4x and 2x primary hybrids from the 3x-2x progenies, and crossing 4x-2x hybrids to produce secondary 3x hybrids. Ploidy and genome segregation routinely occurs during this process and constitutes a major hindrance for selection because this is not easily detectable at the morphological level. This study was carried out to assess the potential of early screening for discriminating ploidy and genome classes in 4x (AAAB)-2x (AA) breeding populations, based on flow cytometry and genome-specific RAPD analysis. Results indicate that progenies of 4x-2x crosses produced predominantly 3x progenies (94.1%). RAPD analysis identified seven genomic classes, dominated by AAA and AAB configurations segregating 1:1 (χ2 = 0.21, P = 0.05). Plant size and bunch weight increased with ploidy level, justifying ploidy-based grouping of progenies for homogenous field evaluation. Similarly, genome-based grouping within ploidy classes is recommended to allow proper evaluation of progenies according to targeted postharvest utilization. Thus, ploidy analysis by flow cytometry and genome determination by RAPD open prospects for enhancing breeding efficiency in the development of triploid bananas or plantains.

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Bruce W. Wood and Larry J. Grauke

(Juglandaceae) ( Manos and Stone, 2001 ) ( Table 1 ). Species differ in not only morphology and habitat, but also in ploidy (i.e., 2 n = 32 vs. 64) with Apocarya section species being diploid (100% of species) and Carya section species being either diploid (40

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Mark W. Farnham, Ellis J. Caniglia, and Claude E. Thomas

Broccoli (Brassica oleracea L. Italica group) breeders routinely use anther or microspore culture to produce dihaploid (diploid), homozygous lines. During the culture process, polyploidization occurs and diploid regenerants can result. However, polyploidization may not occur at all, or it may involve a tripling or quadrupling of the chromosome complement. Thus, regenerated populations must be screened to identify the diploids that are the regenerants most likely to set seed and serve as inbred lines. DNA flow cytometry has proven a useful procedure for determining ploidy of anther derived regenerants. This study was undertaken to evaluate the effect of leaf age and sampling procedures on ploidy determination via flow cytometry. Anther-derived plants were analyzed at a four- to five-leaf stage (transplant stage) and at time of heading (mature plant stage). In addition, leaves were sampled on a given date and stability of the flow cytometry preparations was evaluated over 7 days. Lastly, the stability of ploidy readings of leaves stored at 4°C was examined over a 7-day period. In only one case out of 123 comparative assays did leaf age affect ploidy determination. For that exception, a haploid at transplant stage was a diploid at the mature plant stage. Flow cytometry preparations and also leaves stored at 4°C gave consistent ploidy determinations up to four days after preparations were made or tissue was refrigerated, respectively. These results indicate that broccoli breeders can make flow cytometry preparations on site and send them offsite for flow cytometry analysis. Alternatively, leaves could be refrigerated, sent offsite, and then prepared and analyzed at another location.

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Aliza Vardi, Ilan Levin, and Nir Carmi

among Citrus hybrids obtained from different crosses with ‘Satsuma’ mandarin. Ploidy and Cytoplasmic Male Sterility Another approach for eliciting seedlessness involves the coupling of parthenocarpy with male sterility. Sterility can

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Lin Wu and Hong Lin

The polymerase chain reaction (PCR) and RAPD fragments are potentially useful methods for identifying turfgrass cultivar breeding lines. RAPD markers were studied in 25 vegetatively propagated buffalograss lines using oligonucleotide random primers and agarose-gel electrophoresis to determine their potential for identifying cultivar breeding lines. The variation of RAPD markers was extensive. The RAPD markers produced by one random primer were sufficient to separate the 25 buffalograss lines. Cluster analysis baaed on' the RAPD markers produced by two random primers revealed that the 25 buffalograss lines generally fell into two groups: diploid and hexaploid. Three DNA extraction methods—sarcosyl lysis-chloroform extraction-isopropanol precipitation, sodium dodecyl sulfate (SDS) lysine-isopropanol precipitation, and boiling in the presence of Chelex-100 resin—and fresh or oven-dried tissues were tested for reproducibility of RAPD markers. The three DNA extraction methods, using dry or fresh plant tissues, produced highly comparable RAPD marker profiles. More than 80%1 of the RAPD markers was consistently detected in six replicate analyses. The above studies demonstrate that small quantities (5 mg) of oven-dried leaf tissue and several DNA extraction methods can be used for buffalograss fingerprint studies.

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James McConnell and H. Kamemoto

Floral characteristics, meiotic behavior, and sporad formation were compared in three Dendrobium tetraploids (amphidiploids) and their diploid counterparts. Amphidiploid flowers were larger than those of diploids. Diploid meiotic behavior varied; mean configurations at Metaphase I ranged from 14.3 bivalents and 9.4 univalents to 18.9 bivalents and 0.2 univalents. In amphidiploids, nearly all cells had 38 bivalents. Sporad formation also varied; diploids had 36% to 70% tetrads and amphidiploids had 97% to 100% tetrads. Preferential pairing and small chromosome size may promote bivalent formation in amphidiploids.

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S.L. Grange, D.I. Leskovar, L.M. Pike, and B.G. Cobb

Poor and inconsistent germination is a problem in triploid watermelon. Nicking was shown effective in improving germination in triploid cultivars. In this experiment, we examined the effects of high and low medium moisture, and nicking on diploid and triploid seed germination. Germination for the diploid cultivar was unaffected by any treatment. At high moisture conditions, triploid seed germination was severely reduced to less than 15%, while nicking significantly improved germination up to 40%. However, this increase is still not commercially acceptable. When seed morphological components were measured for each cultivar, triploid seeds had a larger and highly variable air space as compared to the diploid seed. The data confirm that seed germination is not inhibited by the seedcoat alone, but appears to be highly sensitive to excessive water conditions.