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- Author or Editor: Peter D. Ascher x
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Greenhouse and garden chrysanthemums are quantitative short-day (SD) plants for flower bud initiation (FBI) and qualitative (obligate) SD plants for flower bud development (FBD). Continuous or intermittent application of red light in the middle of the dark period (night), inhibits FBI. The chrysanthemum breeding program has been selecting for day-neutral (DN) types, i.e. that will undergo FBI and FBD under any photoperiod. The inheritance of DN was studied using six cultivars (n = 2 SD types, n = 4 DN types) that were crossed in a complete diallel over two crossing periods. Pollinations were replicated and ovules were counted. Histograms of self and cross seed set showed a distribution from 0% to 100%, with the majority of pollinations below 30%. Mean self seed set (2.6%) was less than the mean cross seed set (32.8%), indicating the presence of a self incompatibility system. Parents and F1 progeny were grown under LD conditions (red light, night interruption, 2200-0200 HR) and high temperatures (30 °C day/25 °C night, to screen for heat delay insensitivity). F2 progeny could not be generated due to self incompatibility. The fraction of flowering: non-flowering progeny and the number of days to first flower was recorded on the flowering individuals for comparison with the parents. Due to small progeny numbers, reciprocal crosses were bulked prior to Chi-square tests (1:1, 3:1, 1:3). The number of days to first flower ranged from 27 to 93+ in all progeny with significantly earlier and later outliers present. Most Chi-square tests were not significant, indicating that the inheritance of DN and heat delay insensitivity are not controlled by a single gene. Additive and epistatic effects may also be present.
It should be possible to maintain horticultural clones unchanged forever through asexual generations, as commercial propagators and clonal repositories maintain clonal integrity, disease-free stock plants, or remove mutations. However, unintentional selection for nonhorticultural traits could still be occurring. Accumulations of such traits would be due to the operation of Muller's ratchet and include fertility losses, increases in virus titer, and stunted growth habit. In chrysanthemums, Dendranthema grandiflora. clones separated from sexual cycles for generations become increasingly sterile. Seed set across years, using coefficients of crossability (FCC/MCC), was examined for garden clones (forced through sexual cycles annually) and greenhouse clones (asexual cycles only). Garden clones 40 years old (54-101-11) had only depressed levels of fertility. In other cases (77-AM 3-17), the ratchet was reversed >1 sexual cycle. Greenhouse clones were often completely sterile since their propagation is primarily asexual.
Advanced, two-species CBC individuals were used to create the first-ever, three-species hybrids between P. acutifolius, P. coccineus and P. vulgaris. M6 (2 species) × H15 (3 species) is the only three-species hybrid to date that segregates for diagnostic traits. Three generations of M6 (F2, F3, F4,) were used to create the series. Hybrid breakdown was most severe with M6 F2 × H15, producing 100% cripples that died before anthesis. In M6 F3 × H15 hybrids, segregation for stigma position, flower color, germination type, growth habit, leaf length/width ratios, and seed morphology commenced in the F1 hybrid generation. F, phenotypes, with P. coccineus flowers & seeds and P. acutifolius leaves & growth habit, had severe hybrid breakdown with weak self compatibility; purple seed coats, with or without black circundatus markings, and new flower colors were also produced. F1's with P. vulgaris growth habits were self-fertile and ceased segregating after the F2.
The methods of Wall and York (1957) were used to measure cotyledon position in two populations of three species interspecific Phaseolus hybrids and in the single species cultivars and accessions of P. coccineus, P. acutifolius, and P. vulgaris used as parents. Cotyledon position was represented by the length of the epicotyl as a percentage of the total length of the seedling's stem from the first root initial to the base of the primary node. Progeny of interspecific crosses between P. coccineus and P. vulgaris have been shown to inherit the cotyledon position of the cytoplasmic parent. The objectives of this study were to determine if three species hybrids also inherited the cotyledon position of the cytoplasmic parent, and to determine if P. acutifolius could be distinguished from P. vulgaris by its cotyledon position. Results indicated that the cotyledon positions of the three species hybrids did not differ significantly from the cotyledon positions of cultivars of the species used as the cytoplasmic parent for both P. vulguris cytoplasm and P. coccineus cytoplasm. Further, the cotyledon position of the P. acutifolius accessions did differ significantly from the cotyledon positions of both the P. vulgaris cultivars and the three species hybrid with P. vulgaris cytoplasm. These results suggest that cotyledon position may indeed be a species-specific trait for Phaseolus in Lamprecht's sense of the term.
The snail flower, V. caracalla, was a popular ornamental flowering plant in conservatories at the turn of the century. It's popularity was due, in part, to its showy, orchid-like flowers whose fragrance rivals Stephanotis The indeterminate, vining growth habit can produce plants > 20 feet in height. V. caracalla is of interest for genetic and evolution studies since it is an ancestral species and possesses diagnostic traits of both Phaseolus (coiled style, leaf length/width ratios) and Vigna (> 10 seeds/ovary, long seed pods). However, its reproductive biology and use as an intergeneric hybrid bridge is unknown. Plants were examined for male and female fertility, self compatibility, and cross compatibility. Genotypes were self-incompatible; with one exception, self seed set did not occur following artificial manipulation. Selfed flowers abscised within 1-2 days post-pollination. Accessions were cross-compatible and highly fertile. To date, intergeneric hybridizations performed with P. coccineus --theancestral Phaseolus --have aborted following fertilization.
Lythrum species (Lythraceae), found both in the Old and New Worlds, possess heterostyly (macroscopic differences in anther and style lengths). SI is linked with heterostyly in tristylous L. salicaria, allowing for visual identification of compatibility relationships. Five Minnesota populations of distylous L. alatum (short & long styles/anthers) were examined for fertility and linkage between distyly and SI. Pollen was not inhibited from germination, stigmatic penetration, or stylar growth in compatible crosses. Average cross-compatible seed set for each population was 7-33 seeds/capsule for short- and 27-69 for long-styled plants. With the exception of the Iron Horse Prairie population, there were no significant differences in mean seed set/capsule between genotypes, style morphs, or their interaction for compatible crosses. Zero self seed set predominated, although 0.8±1.8 seeds/capsule were produced by short styles and 1.2 ±2.3 by long styles from Iron Horse Prairie. In those individuals that were SI, pollen tube growth was inhibited following self pollinations.
Abstract
Dehiscence of a mature orchid fruit releases a multitude of seeds — more than a million per capsule in some species. Air currents carry the seeds, but few land on a site permitting germination; even fewer chance upon an environment suitable for development of a mature plant. The seed is microscopic and consists of the bare essentials: a seed coat modified for buoyancy, an embryo of from 8 to 100 cells, and, rarely, a small amount of undeveloped endosperm (2). All orchids require an external source of organic molecules for seed germination or seedling development. After germination, many exist for long periods, the entire life cycle in the case of true saprophytes, deriving carbohydrates and other organic molecules from exogenous sources. Various fungi, in mycorrhizal association with the orchid, provide these complex molecules.
Abstract
Self progenies obtained from bud pollination or from self pollination following high temperature treatment of 7 self incompatible (SI) Petunia hybrida Vilm. plants representing the I1, I4, I6, and I7 generations were tested for SI in both summer and winter greenhouse environments. Five exhibited increased self seed set (pseudo-self compatibility, PSC) after winter pollinations, 1 was more PSC after summer pollinations, and 1 set no self seed in either pollination environment. Comparison of sibling progenies within a line at the I8 generation and differences in PSC between lines at the I7 and I8 generations indicate that inbreeding has not destroyed the possibility of recovering SI.
Abstract
Injection of 100 or 200 ppm 6-furfurylaminopurine (kinetin) into detached Lilium longiflorum (Easter lily) styles before pollination removed the differential pollen tube growth attributable to the self-incompatibility reaction so that both compatible and incompatible pollen tubes reached lengths typical of compatible tubes. Prepollination injections of 50 ppm kinetin produced variable results while injection of 1 or 10 ppm kinetin had no effect on pollen tube growth.
Abstract
Polyacrylamide gel disc electrophoresis of crude protein extracted at room temperature from various plant tissues with 10 to 90% dimethyl sulfoxide (DMSO) in water (v/v) resulted in clear, reproducible protein and isozyme banding patterns. Degeneration of samples stored at -29°C, as indicated by gradual discoloration, began 1 month after freezing in samples extracted with 10-20% and 6 months to 1 year after freezing in samples extracted with 30-60% DMSO. Banding patterns of gels run with discolored samples reflected the degradation in missing bands and indistinct band boundaries. Tissue extraction at 0°C with DMSO did not improve protein patterns in the gels.