, naturally released pollens and difficulty in pollen germination were responsible for the seedlessness of the mutant ‘Ougan’ mandarin. However, the development of mature pollen grains from the microspore mother cell (MMC) in the seedless mutant ‘Ougan
Zhiyong Hu, Min Zhang, Qigen Wen, Jie Wei, Hualin Yi, Xiuxin Deng, and Xianghua Xu
Asma Ziauddin, Mingsheng Peng, and David J. Wolyn
Clear visualization of asparagus (Asparagus officinalis L.) microspore nuclei with common stains such as acetocarmine or DAPI is difficult, hindering cytological analyses. The addition of saturated aqueous ferric chloride solution to Carnoy's I fixative (30 μL·mL-1) resulted in clear visualization of nuclei. A distinct nucleus was observed in uninucleate cells and the vegetative and generative nuclei were clearly visible in binucleate microspores. This method can be used reliably for determination of asparagus microspore developmental stage. Chemical name used: 4′,6-diamidino-2-phenylindole-2HCL (DAPI).
Christopher M. Long, Colleen A. Mulinix, and Amy F. Iezzoni
Microspore-derived callus cultures were obtained by anther culture of `Emperor Francis' sweet cherry (Prunus avium L.). Branches were removed from the field in January and March and forced in the laboratory. When the microspores reached the uninucleate stage, anthers were placed on modified Quoirin and Lepoivre liquid culture medium containing 4.4 μm BA and 4.5 μm 2,4-D. After ≈60 days, callus that emerged from the anthers was placed on woody plant medium supplemented with 1 μm 2,4-D and 3 μm 2iP and routinely transferred. The resulting 270 callus cultures were screened for two allozymes heterozygous in `Emperor Francis', Pgi-2 and 6-Pgd-1. Of the 270 callus cultures, 154 expressed only one allele each for Pgi-2 and 6-Pgd-1; thus, they were considered microspore-derived. The microspore-derived callus cultures can be used as a linkage mapping population. Chemical names used: 6-benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); N6-(2-isopentenyl)-adenine (2iP).
Ram K. Birhman, Sylvain R. Rivard, and Mario Cappadocia
Using restriction fragment length polymorphism (RFLP) analysis, the genetic architecture of some anther-culture-derived S. chacoense Bitt. plants was studied, and their origins were elucidated. Our RFLP analyses showed that 1) several plants, even of different ploidy but otherwise genetically identical (clones), can be regenerated from callus originating from a single microspore and, conversely, that 2) some plants regenerated from single callus can have different genetic constitutions and, therefore, must have originated from two different microspore. These findings imply that previous anther culture efficiency estimates might have to be reconsidered.
William L. Summers, Juan Jaramillo, and Theodore Bailey
Anthers of L-680A', `Licato', and `Ailsa Craig' tomato (Lycopersicon esculentum Mill.) were plated on Doy's basal medium 1 to determine whether microspore developmental stage and anther length influence anther callus production. Although calli were induced at all stages of anther development, anthers containing prophase I-stage microspores produced the highest frequency of calli. Fewer calli were produced as microspores approached the uninucleate and binucleate pollen stage. Callus diameter also decreased as anther development progressed. Significantly larger calli were produced from prophase I than later-stage anthers. Time of anther harvest (morning vs. afternoon) did not significantly affect callus number or diameter. Anther and flower bud length both were significantly correlated with anther developmental stage, the number of anthers producing calli, and mean calli diameter. In each case, anther length exhibited a significantly better correlation than bud length.
I.E. Yates and Darrell Sparks
Catkin external morphological characteristics of a protogynous (`Stuart') and a protandrous (`Desirable') cultivar of pecan [Carya illinoensis (Wangenh.) C. Koch] were related temporally to the differentiation of microspore and pollen grains. Reproductive cell development was divided into seven periods based on evaluations of number, location, and intensity of staining of the nucleus and/or nucleolus; and vacuolization and staining intensity of the cytoplasm. Catkins with anthers and bracteoles enclosed by bracts did not have reproductive cells that were matured to free microspore. Free microspore developed only after bracteoles became externally visible. The Period 1 nucleus was at the periphery of the cell and a large central vacuole was present; at Period 2, the nucleus was at the center and vacuolation had been reduced. As the angle between the bract and catkin rachis increased to 45°, vacnolation was reduced as the nucleus enlarged and moved to a central location in the microspore (Periods 3 and 4). The majority of the pollen grains were binucleate, and the generative nucleus became elliptical (Periods 5 and 6) by the time anthers became externally visible. Acetocarmine staining intensity of cellular components masked the presence of the generative nucleus (Period 7) just before anther dehiscence. Staining reaction for protein was positive from Period 1; starch from Period 3; lipids and polyphenols from Period 5. The mature pollen grain was abundant in stored reserves of starch and lipids and had a wall with a thicker exine than intine as demonstrated by acetolysis.
Pernell Tomasi, David A. Dierig, Ralph A. Backhaus, and Kathleen B. Pigg
Dongmei Wei, Huimin Xu, and Ruili Li
pollen, anthers are divided into seven stages: sporogenous cell, microspore mother cell (MMC), tetrad, early microspore, late microspore, early bicellular pollen, and mature pollen. In each stage, staminate buds have different sizes ( Fig. 1C ), and
Dongmei Wei, Chao Gao, and Deyi Yuan
microsporogenesis and anther development. The development of anthers is complicated. Cells in different anther tissues undergo different processes that lead to conspicuous changes in morphology and structure; these processes include meiosis in microspore mother
Weiping Zhong, Zhoujun Zhu, Fen Ouyang, Qi Qiu, Xiaoming Fan, and Deyi Yuan
of the middle layer and tapetum and delayed degeneration of the tapetum ( Kim et al., 2016 ). Different pollen development characteristics, such as the duration of each stage of pollen development, cytokinesis during meiosis in microspore mother cells