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- Author or Editor: Peter D. Ascher x
- Journal of the American Society for Horticultural Science x
Abstract
Genotypes and pollination dates, but not cuttings, contributed significantly to variance in percent pseudo-self-compatibility (PSC) from self pollinations of F2 sibling Nemesia strumosa Benth. plants. Genotypes selected from different families which were self- and cross-pollinated on several dates in 4 locations having varying environmental conditions responded differently to environments. Correlations between seed set and daily temperatures were significant in only a few cases. Tests of the effect of plant age on seed set revealed that plants generally set fewer seeds following either self- or compatible-pollinations when old, but the ratio of self- to compatible-cross seed sets (percent PSC) varied with genotype.
Commercial chrysanthemums are short day (SD) plants. Recently, several day neutral (DN) garden genotypes have been identified. Both glasshouse and garden cultivars vary in heat delay insensitivity (HDI). This research analyzed yield components (seed set, germination, yield potential) and tested a DN/HDI ideotype for its effectiveness. Progeny from a 6 × 6 diallel were embryo rescued, clonal ramats were grown in two environments (glasshouse—long days; field—long to short days) and evaluated for flowering, early flowering response groups, thermozero temperature response, low long day leaf number (LDLN), high leaf initiation rates, and low mean stem lengths of the terminal shoot. Self seed set ranged from 0% to 8% while outcross seed set was 0% to 92%. General and specific combining ability were highly significant for seed set, the reciprocals, and their interactions. Germination averaged 67%, while yield potential was 44%. Cotyledon pigmentation in embryo rescued seedlings was 7% albinos, 15% anthocyanin (transposable elements), and 78% normal (green). SD parents did not flower in either photoperiod although PPSL-10 carried alleles for DN. SD x DN crosses produced some DN progeny and fit a 1:3 chi square ratio (DN:SD), indicating DN to be recessive. However, DN x DN crosses also fit a 3:1 chi square ratio, due to HDI. No progeny flowered within the 3 to 6 week ideotype; visible bud date had a heritability of h 2 = 0.50. Most progeny were within the LDLN range (h 2 = 0.72). Several leaf initiation rates exceeded the ideotype (h 2 = 0.003); plant height also matched the ideotype (h 2 = 0.66). Both visible bud and flowering dates require significant improvement before progeny match the DN/HDI ideotype.
Commercial garden and greenhouse chrysanthemums [Dendranthema ×grandiflora (Ramat.) Kitam. (syn. Chrysanthemum xmorifolium Ramat.)] are facultative short-day plants for flower bud initiation, obligate short-day plants for flower bud development, and are categorized into short-day response groups. Flower initiation can be delayed by high night temperatures. Recent research has identified true day-neutral genotypes. The purpose of this investigation was to test environments for selecting genotypes that are both day-neutral and heat-delay insensitive. One greenhouse and 18 garden genotypes were selected. A series of environments were used to select for day-neutral genotypes and then differentiate between these genotypes for heat delay insensitivity: short days, long days/red light, long days/far red light and high temperatures, and natural day lengths under field conditions. Day-neutral selections from these environments were then grown in a fifth environment of long days/continuous far red and red light with high temperature. Data were collected on the number of days to first and third flower, long day leaf number, stem length, number of strap-shaped leaves subtending the terminal flower, internode lengths, number of nodes with axillary branching, and flower bud development of the first to the sixth flowers. Genotypes required 3 to 8 weeks for complete flower bud initiation/development. Flowering responses in the first four environments were highly significant for both the first and third flowers. Genotypes ranged from obligate short-day to day-neutral for the first six flowers. Three day-neutral genotypes were selected that differed significantly for all traits in the fifth environment; flower bud development with the first six flowers occurred with only one genotype, 83-267-3. Broad sense heritability estimates ranged from h2 = 0.75 for number of nodes with axillary branching, h2 = 0.79 for long day leaf number and number of strap-shaped leaves, to h2 = 0.91 for stem length. An ideotype for day-neutral and heat-delay-insensitive garden chrysanthemums was developed for use in breeding programs.
Male and female fertility, seed germination, and progeny fertility were used to determine cultivar fertility in species of Lythrum. One short-, 11 mid-, and six long-styled cultivars were included in this study. Duplicates of several cultivars from different nurseries and three unknown cultivars from Minnesota gardens were also collected. Plants from 17 Minnesota and one Wisconsin population of L. salicaria served as fertile male and/or female testers. Pollen stainability (usually 100%) showed low levels of male gamete abortion. Pollen size within and among anther type varied widely; possible 2n gametes were present in primarily the short- and mid-anther morphs. Seed production per capsule from legitimate cross-pollinations, using cultivars as male parents with Minnesota or Wisconsin female testers, averaged 48 ± 36 across style morphs. Cultivars differed as males, as did anther morphs. With female fertility tests, seed set per capsule ranged from zero to 152 and averaged 54 ± 40 in legitimate pollinations (i.e., pollinations between stamen and styles of the same length). Seed set for other crosses showed similar trends. Only `Morden Gleam' produced no seed with all legitimate pollinations, although illegitimate selfs or interspecific crosses produced seed. Seed from legitimate crosses of L. salicaria × cultivars had 30% to 100% germination. Common male and female parents within each legitimate crossing group were not significantly different. This study showed that the cultivars are highly fertile when used as male or female parents with wild purple loosestrife, native species (L. alatum Pursh.), or other cultivars. Thus, cultivars grown in gardens could serve as pollen or seed sources for the continued spread of purple loosestrife. The implications of cultivar fertility, especially interspecific F1 hybrids, is discussed in relation to the spread of noxious weeds in wetlands.
Chrysanthemum [Dendranthema ×grandiflora Tzvelv. (syn. Chrysanthemum ×morifolium Ramat.)] breeding programs have been selecting for reduced expression of self-incompatibility (via pseudo-self-compatibility) to create inbred families with selected genotypes to serve as parents for F1 hybrid chrysanthemum seed production. However, it is not known to what extent inbreeding is affecting fertility in this outcrossing, heterozygous species. The objective of this research was to assess male/female fertility changes (gain/loss) in successive inbred generations of chrysanthemums. Pseudo-self-compatible chrysanthemum parents (n = 41 inbred, noninbred, and recombinant inbred) were chosen for fertility analyses. As many as three generations of inbreds (I1, I2, and I3) from self-pollinations were created using rapid generation cycling. Female and male fertility levels of the parents and all derived inbred populations were assessed using outcross seed set and pollen stainability, respectively. Average seed set ranges were 0.3% to 96.1% (inbred parents), 24.5% to 38.5% (noninbred parents), and 0.9% to 85.1% (recombinant inbred parents); these began decreasing in the I1 and continued to decline steadily into the I3. Statistically significant (P < 0.05) decreases in seed set occurred in n = 23 (56.1%) inbred families; the remaining inbred families had similar or higher fertility than the parents. Pollen stainability was >50% for the parents, but began declining in some inbred families as inbreeding progressed. Fertility reductions were attributed to inbreeding depression. Lack of significant fertility losses in other inbred families demonstrates the opportunity of selection of fertile inbred parents for use in hybrid seed production.
Abstract
The exudate produced on the stigma of mature flowers of L. longiflorum Thunb. did not adversely affect pollen tube growth or the self-compatibility reaction when injected into lily styles before, 6, or 12 hr after pollination. Stigmatic exudate diluted with an equal volume of distilled water before addition to the style had no effect on pollen tube growth when injection occurred before or 6 hr after pollination. Although injection of exudate alone 24 hr after pollination or injection of diluted exudate 12 or 24 hr after pollination retarded pollen tube growth, the addition of exudate or diluted exudate did not obscure the self-incompatibility reaction. Stigmatic exudate appears to be an excellent milieu in which to carry exogenous materials into the environment of pollen tubes of L. longiflorum growing in vivo.
Abstract
Compatibly- and incompatibly-pollinated detached styles of Lilium longiflorum were incubated for various time periods at 39°, 31°, 24°, 19° and 12.5°C to elucidate the effect of high and low temperatures on the self-incompatibility reaction. High temperatures during pollen tube growth prevented the incompatibility reaction, as incompatible pollen tubes reached lengths similar to those of campatible tubes in styles incubated at 39° and 31°C. Between 12 and 24 hr post-pollination the rate of compatible tube growth at 24°C (room temp) doubled while the rate of incompatible tubes continued unchanged. Incompatible pollen tube growth decelerated after 2 days at 19°C resulting in a significant difference between compatible and incompatible tube length 3 days after pollination. In styles incubated at 12.5°C the lengths of compatible and incompatible pollen tubes did not differ significantly until 6 days after pollination when incompatible tubes were shorter. The self-incompatibility reaction occurred at low temperatures, for growth of incompatible tubes was restricted to lengths typical of those grown at room temperature.
Abstract
An average Easter lily bulb with 100 scales may produce 8000 or more bulbs in 6 weeks when 1 mm thick cross sections from the scales are cultured in the Linsmaier-Skoog medium as modified by Sheridan and supplemented with 0.03 mg/liter NAA. Continuous darkness at 25°C increased bulb number and size at the expense of leaf number and size while a cycle of 16 hours cool white fluorescence at 1.6 klx (150 ft-c) and 8 hours dark at 25°C suppressed bulb formation but enhanced leaf formation, root weight, and fresh weight of callus. Root numbers were equal in both environments. Cultures incubated at 18.3° exhibited no measurable growth after 6 weeks. Explants from the distal part of the bulb scale will grow only with growth regulators present.
Abstract
Bulblets of Lilium longiflorum generated in vitro in the dark at 30°C produced leaves more rapidly and more completely after transplanting to vermiculite than those generated in vitro at 25°. The product of temperature × time (days) was equalized by varying the number of days at the 2 temperatures to make treatments comparable. Therefore, the effect of temperature in vitro was not due to a linear relationship between bulblet development and the product of temperature × time. Bulblets formed at 30°C for half of the temperature × time product of the tissue culture period produced leaves after transplanting at rates similar to those of bulblets generated at a constant 30°C. Exposure of bulblets generated in vitro at 25°C to 4° for 2 weeks before planting in vermiculite resulted in leaf production not significantly different from that of chilled or non-chilled bulblets generated in vitro at 30°C. However, chilling significantly increased fresh weight of bulblets produced in vitro at either temperature. The data suggest that temperature during in vitro development affects Easter lily bulblet dormancy as measured by leaf production.
Abstract
Bulblets from bulb-scale explants of Lilium longiflorum Thunb. cvs. Ace and Nellie White cultured in darkness on a semisolid Linsmaier-Skoog medium supplemented with 0.03 mg/liter α-naphthalene-acetic acid (NAA) bore no leaves when produced in vitro at constant 30°C but often did when produced at constant 25°. In vitro temperature regimes involving both 25 and 30° resulted in the largest number of leaves per explant. Time in vitro in each temperature regime was calculated to provide equal heat units so that differences could not be explained by a linear relationship between development and temperature × time. Physiological state of explants, measured by time lily bulbs were stored at 4° before tissue culture, interacted with in vitro temperature. Explants from bulbs stored 110 days or less produced significantly fewer but significantly larger bulblets at constant 25° as compared to constant 30°. This difference was not apparent when explants were taken from bulbs stored at 4° more than 110 days. In an experiment with explants from bulbs stored 80 days, there was no significant difference between ‘Ace’ and ‘Nellie White’ in number of scales per bulblet at either 25 or 30° but bulblets of both cultivars contained significantly fewer scales if generated at 30°. Mean width of meristems in ‘Ace’ bulblets was significantly greater when produced in vitro at 30°. Neither initiation of bulblets nor bulblet development appeared controlled by apical dominance.