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Sinchieh Liu and Martha A. Mutschler

The transfer of multigenic traits into tomato has been slow due to interspecific barriers (hybrid breakdown) found in the F2 of the Lycopersicon esculentum × L. pennellii cross (esc × pen), including blocks in normal reproductive development and nonfecundity. In a typical (esc × pen) F2 population, failure to flower and premeiotic blocks in pollen development occurred in 2% and 11% of the population, respectively. The remaining plants showed a mean of 37% stainable pollen. Twenty three percent of the F2 plants set seed, with an average of 4.5 seeds/fruit. An average of 33% of the stainable pollen from the 7 F2 plants with the highest stainable pollen measurements germinated in vitro, but only 4 of these 7 plants set seed. Thus, percent stainable pollen is not an adequate predictor of fecundity, and the non-fecundity in the F2Le plants must involve barriers occurring after pollen germination.

A method was developed which greatly reduces or eliminates each of the F2 barriers. The method and its efficacy on each of the aspects of hybrid breakdown will be discussed.

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Boniface B. Dumpe and Rodomiro Ortiz

Current efforts to produce improved genotypes of plantain and banana (Musa spp.) depend on crossing female-fertile clones with accessions that produce viable pollen. Musa accessions (168) were screened for production of viable pollen based on staining with acetocarmine glycerol jelly. Diploid hybrids and landraces produced significantly more pollen than triploids and tetraploids, suggesting more successful crosses when using diploid accessions as male parents. There was a positive correlation between the amount of pollen produced and the level of viability in both hybrids (r = 0.65, P≤ 0.01) and landraces (r = 0.61, P≤ 0.01). This finding suggests that closely associated genetic factors determine these characteristics in Musa, while environmental conditions also may influence the quality and quantity of pollen produced. Pollen production at anthesis was absent in 28 accessions. Of the 140 accessions with pollen, 67 were sufficiently fertile for use as male parents in the breeding program.

Open access

Nicholi Vorsa, Gojko Jelenkovic, Arlen D. Draper, and William V. Welker

Abstract

Percent fruit set, fruit size, total seeds/berry, developed seeds/berry, percent developed seeds/berry, and percent pollen stainability were examined in 4x × 5x and 5x × 4x progenies derived from Vaccinium ashei Reade/V. corymbosum L. pentaploid hybrids backcrossed to V. corymbosum. All fertility parameters indicated that the BC1 progenies were more fertile than the pentaploid hybrids. Pollen stainability indicated that the BC1 derivatives were less fertile than the parental species. All fertility parameters were significantly and negatively correlated with chromosome number, which ranged from the tetraploid (2n = 4x = 48) to pentaploid (2n = 5x = 60) levels within these progenies.

Open access

J. W. Carmichael, W. B. Sherman, and S. C. Schank

Abstract

Recent studies in pollen germination, fertilization and embryo sac development have led to a search for a rapid nuclear stain. Pontacyl violet 6R (C.I. 16640) proved to be excellent in animal tissues (4) and was therefore tested for effectiveness with plant tissues.

Free access

John R. Stommel, Ruth S. Kobayashi, and Stephen L. Sinden

Somatic fusion hybrids created between tomato and Solanum ochranthum, a wild nontuber-bearing diploid species that is genetically isolated from tomato, were evaluated in an effort to introgress traits from S. ochranthum into tomato. Pollen stainability and pollen tube growth examination demonstrated that little or no viable pollen was present in tetraploid and hexaploid fusion hybrids. Aneuploidy was noted in a small percentage of these hybrids. Use of tetraploid and hexaploid fusion hybrids as female parents in backcrosses to diploid and tetraploid tomato was studied. Chemical treatments that induce either chromosomal recombination or reduction may be advantageous for overcoming difficulties in introgression of these wide hybrids into tomato.

Free access

Scott Reid, Judy Harrington, and Harrison Hughes

Distichlis spicata var. stricta (Torrey) Beetle is a native grass that tolerates salt, high pH, and some heavy metals. It has been proposed for use in several challenging environments, including mine spoils and salt-impacted areas of golf courses. But, its widespread use has been hindered by several factors, one of which is poor seed set. Because chromosome numbers are variable and some genotypes are aneuploids, there was concern that pollen viability in some genotypes was low. Pollen from several genotypes failed to germinate in vitro on four artificial media prepared with various levels of osmoticum. However, hand pollination in vivo resulted in profuse pollen germination for all genotypes tested. Germination on pollinated stigmas was observed at intervals beginning 2 h after pollination with a fluorescence microscope using aniline blue and acridine orange stains and in bright field using toluidine-O stain. Very young stigmas seemed unreceptive and, while pollen would germinate, the pollen tubes would not grow down through the style. On receptive stigmas, many pollen tubes grew down toward the egg and some reached it within 24 h. There was no evidence of impaired fertility. Aniline blue was the best method for observing pollen tube growth through the style, although toluidine-O was adequate for observing germination on the stigmatic surface.

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Eva Domínguez, Jesús Cuartero, and Rafael Fernández-Muñoz

Using soil bed cultivations as controls and under two temperature regimes (maximum/minimum ≈20/4 °C and 25/10 °C), effects of container volume (16-, 10-, and 3-L pots) on in vitro germination, in vivo tube growth, acetocarmine staining, and quantity of pollen of tomato [Lycopersicon esculentum Mill. `Moneymaker', L. pennellii (Corr.) D'Arcy accession PE-45, and of the corresponding F1 hybrid] were studied. Under the 20/4 °C regime, in comparison with soil-bed cultivated control plants, the cold sensitive cultivar, Moneymaker, grown in the two smaller pots showed significant increases of in vitro pollen germination, acetocarmine staining, and number of pollen grains produced per flower. Similar results were observed with the F1 except for the number of pollen grains which were not significantly different. Pollen of accession PE-45 was unaffected by cold and no container effect was detected. Results of in vivo pollen tube growth in `Moneymaker' at the 20/4 °C regime showed that fruit set was only possible in 3-L pots. Reduction of the negative effects of cold on pollen from plants grown in the 3-L pots may be explained in part by the daytime rise of root-zone temperatures that did not occur in the 10- or 16-L pots or in the soil bed. Therefore, fruit production of tomato plants grown under low temperatures in small pots may not be a valid predictor of commercial winter fruit production of plants cultivated in soil beds.

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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.

Free access

A.M. Shirazi and P.S. Muir

There is increasing interest in using methanol and other alcohol fuels as an alternative energy source in the United States and developing nations. However, methanol-fueled vehicles have higher direct emissions of formaldehyde (HCHO) than gasoline-fueled vehicles, which has led to concern about increases in atmospheric concentration of HCHO. Formaldehyde at concentrations of 300, 600, 900, and 1200 μM reduced germination of hydrated Douglas-fir (Pseudotsuga menziesii) pollen in vitro. HCHO concentrations and pH in media containing pollen decreased during the 25-h incubation, with decreases proportional to HCHO concentration. This effect was not seen with heat-killed pollen, which suggests a detoxification mechanism. Ion leakage (measured as electrical conductivity) of pollen increased within 20 h in all HCHO treatments compared to controls. Stress also was indicated by TTC staining, which also decreased after HCHO treatment compared to controls.

Open access

Ernest D. P. Whelan, C. A. Hornby, and K. O. Lapins

Abstract

Pollen viability and meiosis of propagates of irradiated Prunus avium L. cv. Lambert were studied to investigate changes in pollen viability and induced chromosome changes. These studies revealed significant differences in pollen viability as measured by propiono-carmine stainability, among propagates and between years. Some propagates showed significantly greater annual variation than others. Propagates of a potentially chimeral nature exhibited significant variation among secondary branches, but not among the blossoms within such branches.

Meiotic studies of 12 propagates with unchanged pollen viability did not show chromosomal abnormalities other than those observed in parent ‘Lambert’ material. Studies of 19 propagates with reduced pollen viability showed 11 instances of translocation or inversion hybridity, or greatly increased univalent frequency compared to the parent clone.