The occurrence of bacteria in different tissues was studied using field-grown strawberries, in vitro-grown strawberries, wild strawberries, and aseptically germinated strawberry seedlings. Strawberry has a number of endophytic bacteria in its the internal tissue, most of which appear to be nonpathogenic. In the in vitro-grown strawberries, all identified isolates were in the genus Pantoea. In field-grown garden and wild strawberries the most common genera were Pantoea and Pseudomonas. Location of eubacterial inhabitants within strawberry tissue sections was studied by in situ hybridization. Bacteria were detected in flower stalks, leaf stalks, leaves, stolons, berries and aseptically germinated seedlings. The existence of bacteria in seeds and seedlings suggests that bacteria are able to move up to the generative tissue and, ultimately, to the next generation, forming a symbiosis-like chain of plant-bacteria coexistence.
S. Kukkurainen, A. Leino, S. Vähämiko, H.R. Kärkkäinen, K. Ahanen, S. Sorvari, R. Rugienius, and O. Toldi
M. L. Meyer and F. A. Bliss
Kiwifruit (Actinidia deliciosa) is a functionally dioecious plant where fruit size is dependent on number of seeds set. Pollen fertility was estimated in 1990 and 1991 by percentage stainability and percentage germinability in vitro. Profiles of the isozymes AAT, GPI and PGM were used to assess if any large differences in pollen fertility could be attributed to genotypic variation. Based on these three isozymes, eight different genotypes were discovered. Although significant differences were found among vines within orchards and among orchards, all vines can be considered good pollenizers (stainability > 87%). A positive correlation was found in 1991 between percentage stainability and percentage germination.
M.R. Pooler and R. Scorza
publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.
Charlotte R. Chan and Robert D. Marquard
The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.
Michael J. Tanabe and Nicole Wakida
Noni, Morinda citrifolia, is receiving a lot of attention for its potential medicinal effects. Hawaii is an ideal growing environment for this plant, where it has been used for many purposes, including medicinal ones, by ancient Polynesians. Currently, there is a rapidly developing noni industry in the state of Hawaii. Propagation of this plant is almost exclusively by seeds, and germination generally requires a couple of months without preconditioning or about a month if mechanically scarified. We developed an in vitro protocol that significantly improves percent germination rate by altering incubation temperature and the in vitro culture basal medium. Germination time was decreased to 4 days when the embryo was extracted and exposed to 31 °C. A basal medium containing 1/2 Murashige and Skoog (M&S) salts was the most effective in reducing germination time and increasing percent germination. Stem pieces obtained from in vitro-propagated seedlings produced callus when explanted in 1/2 M&S containing various levels of naphthalene acetic acid (NAA). The most effective treatment was 0.5 μm NAA and the least effective treatment was 2 μm NAA. Treatments without NAA did not produce callus. Calli treated with 4.40 μm 6-benzylaminopurine (BA) or 8.80 μm BA were the most effective in promoting caulogenesis. We also demonstrated that the number of first generation seedlings produced from each embryo could be increased by treatment with 8.80 μm BA.
Michael E. Compton
Several methods have been published on shoot regeneration from watermelon cotyledon explants. The major differences in regeneration protocols include the light environment in which seeds are germinated and the cotyledon region used. The purpose of these experiments was to compare the two main protocols for plant regeneration and develop one general procedure. To fulfill this objective, seeds were germinated in vitro in darkness or 16-hr light photoperiod for 7 days. Cotyledon explants from four watermelon cultivars (`Crimson Sweet', `Minilee', `Sweet Gem', and `Yellow Doll') were prepared from both dark- and light-grown seedlings. Apical and basal halves were obtained by making a cut across the cotyledon width. Apical and basal quarters were made, for comparison, by cutting apical and basal halves longitudinally. All explants were incubated on shoot regeneration medium for 6 weeks followed by a 3-week cycle on shoot elonga-tion medium. The percentage of cotyledons with shoots was 1.7-fold greater for cotyledons derived from seedings incubated in darkness than those germinated in light. Shoot formation was about 10-fold greater for explants from cotyledon basal halves and quarters than apical halves and quarters. According to these results, the best watermelon regeneration protocol should consists of basal explants from in vitro-germinated seedlings incubated in the dark for 7 days.
I. David van der Walt and Gail M. Littlejohn
This paper is a revision of a chapter of a MS thesis submitted by I.D. van der Walt to satisfy the requirements in plant breeding at the Univ. of Stellenbosch. We thank Frikkie Calitz and Marieta van der Rijst for their assistance in statistical
Hector G. Nunez-Palenius, Daniel J. Cantliffe, Harry J. Klee, and Don J. Huber
Pollen germination timing has a paramount role in fertilization of a flower. Rapid germination and outgrowth of a pollen tube that penetrates the stigma is required. Physical and biological factors can affect pollen germination timing. The objective of this study was to determine if ACC oxidase antisense gene expression could influence in vitro pollen germination and in vitro pollen tube length growth. A transgenic (ACC oxidase antisense) `Galia' male parental line had a reduced fruit set compared to its wild type. Likewise, embryo abortion and empty seeds after self-pollination in a `Galia' male parental line were observed. Wild type and transgenic `Galia' male parental line melon plants were grown in a greenhouse according to the practices of Rodriguez (2003). Male flowers were collected from these plants between 10 to 12 am; pollen was obtained by dipping the anther in germination medium (10.25% sucrose, 0.031% calcium nitrate, 0.015% boric acid, 0.0075% KNO3, and 0.016% MgSO4) at 25 °C and analyzed immediately, either for total percentage of germination after 5 minutes of incubation or to measure pollen tube growth rate every 5 minutes during 1 hour. Each flower provided an average of 250 pollen grains. Assays were conducted by using the “Hanging Drop Method” (Okay and Ayfer, 1994). Percentage of pollen germination in WT `Galia' male parental line was greater than the transgenic line. Likewise, in vitro pollen tube growth in wild type `Galia' melon was greater than pollen from the transgenic line. Possibly the ACC oxidase antisense gene expression in `Galia' male parental line may have had an influence on the reduced fruit set observed.
Vladimir Orbović, Manjul Dutt, and Jude W. Grosser
decrease of abscisic acid (ABA) levels in seeds ( Farnsworth, 2000 ). Thus, our data suggest that the change in ABA levels in older seeds did not affect their subsequent germination in vitro. Another possibility is that ABA levels did not change in seeds
Vital Hagenimana, Ronald E. Simard, and Louis-P. Vézina
Coopération Institutionnelle Laval/UNR financed by Canadian International Development Agency. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked