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Kim E. Hummer, Chad E. Finn, and Michael Dossett

chromosomes, ploidy, or gene recombination. Not understanding genetics or mutation, he denied Mendel’s theory throughout his career, although his results were supportive. This article has two objectives. The first is to broadly summarize Burbank’s work on

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Jia Tian, Yue Wen, Feng Zhang, Jingyi Sai, Yan Zhang, and Wensheng Li

on the relationship between cell division and fruit size. Young leaves were also collected separately for ploidy determination. Fruit of each cultivar were fixed in formalin–aceto-alcohol (FAA) solution to measure fruit cell size and number. In

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J.R. Bohac

Sweetpotato, Ipomoea batatas is in the morning glory family, Convolvulaceae, genus Ipomoea, group Batatas. It has many wild Ipomoea relatives that serve as a reservoir of many needed pest and stress-resistance genes. A major barrier to introgression of useful genes is the ploidy gap—sweetpotato is a hexaploid and wild Ipomoeas are diploids and tetraploids. The wild species can be successfully crossed using 2n pollen or by first increasing ploidy by colchicine treatment. The ploidy of such hybrid offpsring can be determined by DNA flow cytometry. My objective was to develop a technique to determine DNA content in Ipomoea and values for DNA content for the major Ipomoea species using the EPIC flow cytometer with a UV detector. Nuclei were extracted and pretreated with cellulase and pectolyase before staining with propidium iodide (PI). A highly linear relationship was found between the DNA content determined by DNA flow cytometry and the ploidy of the closest sweetpotato relatives as determined by chromosome counts. These species were diploid I. trifida, tetraploid I. batatas, and hexaploid I. batatas. DNA content was most similar among other diploid Ipomoea species in the group Batatas and was significantly different in other Ipomoeas not in group Batatas.

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Charles J. Simon and John C. Sanford

A method is described for separating large and small pollen effectively from a heterogeneous mixture. This method potentially is applicable to separation of pollen grains of different ploidy levels, since “unreduced” 2n pollen is larger than normal pollen (n); it might then be used to increase the efficiency of a breeding program employing sexual polyploidization and to diminish crossing inefficiencies in interploid crosses.

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J. W. Bonner, R. M. Warner, and J. L. Brewbaker

Abstract

Peroxidases from certain Musa spp. isolated using horizontal Polyacrylamide gel electrophoresis revealed 4 major zones of activity and 15 separate peroxidase bands. Good agreement was obtained among cultivars of different ploidy groups when composite zymograms were constructed from gel data and compared to a current taxonomic classification. Three clones of unknown origin were genotypically classified as ‘Hapai’ (AA); ‘Tuu Gia’ (AA); and ‘Eslesno’ (AAB).

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Josh A. Honig, Vincenzo Averello, Stacy A. Bonos, and William A. Meyer

polyploidy and aneuploidy can complicate kentucky bluegrass breeding efforts; however, apomixis allows this species to propagate diverse and odd ploidy levels, which results in many genetically distinct individuals ( Huff, 2010 ). This high level of diversity

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Maxine M. Thompson

The U.S. Dept. of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR), Corvallis, Ore., maintains Rubus germplasm representing worldwide diversity of the genus. Chromosome numbers were counted for 201 plants representing 124 taxa (species and varieties). There are new reports for 42 taxa, confirmation for 72 previously reported, and 10 counts for plants unidentified to species. The basic chromosome number was seven, and ploidy levels ranged from 2x to 12x.

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A. F. Iezzoni and A. M. Hancock

Abstract

Pollen samples from 4 sour cherry (Prunus cerasus L.) and 13 sweet cherry (P. avium L.) cultivars were examined by scanning electron microscopy (SEM). Pollen size did not differ significantly between species or ploidy level. Variability in size both within and among cultivars was greater in sour cherry than in sweet cherry. Giant pollen grains occurred in a low frequency in both sweet and sour cherry, equatorial diameter being responsible for the increased size.

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Yinping Shi, Qiangsheng Wang, Guangfang Zhou, and Congyi Sui

Plant mutation induced with colchicine, disturbance of chimeras has long been unsolved. Authors used embryo culture in vitro induced with colchicine for inducing genome of embryonic cells of diploid apple to be doubled, cell doubled differentiated into adventitious shoots, and then were culture into plantlets. By morphological preselection, plants induced hundreds of genotypes had been obtained. To identify ploidy variation of three histogenic layers of shoot apices, sections of shoot apices of 284 plants were identified. Two-hundred-forty-nine tetraploid plants were selected. Entire mutants accounted for 98%, chimeras 2%. This proved that induction in vitro could indeed eliminate disturbance of chimeras and was a new induction technique simply and effectively. Accurate rate of morphological preselection was confirmed by 87.7% by sections of shoot apices. The identification of ploidy of mutated plants of apple in vitro induced with colchicine, the method of combining morphological preselection with sections of shoot apices had advantages over that of chromosome count. First, the method is simple, saving time and labor, with a high success rate and reliable results. Second, whether the mutated plants were chimeras and chimera structures could be known. Main criteria of identifying ploidy by sections of shoot apices are the size of cells, nuclei, and nucleoli and numbers of nucleoli of three histogenic layers of shoot apices. Morphological characters of tetraploid were dumpy, thick, and strong stem with short internodes; small petiole angle; broad-round thick leaves with dark green color; round leaf base; thick and sharp-pointed sawteeth; protruding and clear main vein.

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L. E. Cockerham and G. J. Galletta

Abstract

Pollen stainability, frequency of unreduced pollen grains, and pollen diameter were examined in 13 species and 4 interspecific hybrids of Vaccinium comprising 3 ploidy levels. Pollen in the tetraploid species was potentially more fertile (as judged by stainability) than in the diploid species. Pollen stainability in the hexaploids was not different from the diploids or tetraploids. Four pollen viability classes (good, fair, poor, and very poor) were established among species. Practically all of the species studied produced unreduced pollen grains. Mean pollen diameter was 11% larger in the tetraploids than in the diploids and 11% larger in the hexaploids than in the tetraploids. The normal pollen diameter ranges for the 3 ploidy levels of Vaccinium were calculated and presented as a possible taxonomic tool.

Genetic, rather than seasonal or environmental differences, appeared to account for the major portion of the interclonal and interspecific variation observed in pollen stainability and in the frequency of unreduced pollen grains.

Frequent irregularities observed were empty pollen grains and granular, unstained pollen, which were assumed to represent early postmeiotic abortions. Meiosis was studied in a representative species of each ploidy level. Pairing and segregation were essentially normal, but a few multivalents or pseudo-multivalents (bivalents secondarily associated) were observed in the hexaploid species.