statistical analysis. T.L. Maguire is the recipient of an Australian Postgraduate Research Award. 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
It has been speculated for many years that crop yield diminution may be due to the possible adverse effects of pesticidal sprays during the blooming period on pollen germination and fruit set. To realize the toxicity of pesticides on the reproductive physiology of mango, pollen germination, both in vitro and in vivo, under the constrain of pesticides were conducted. The results showed that among all the pesticide tested, Lannate and Tamaron were the least toxic ones to mango pollens germinated on agar medium incorporated with pesticides. Pesticides when sprayed on the surface of germination medium had strong adverse effect on pollen germination. Except for Tamaron, the fertilization of mango flowers were extremely sensitive to pesticidal sprays 2 hours before or 4 hours after hand pollination. Fertilization and initial fruit set were not or less influenced by pesticides for flowers sprayed 24 hours after pollination.
CoopeΜration 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
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.
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.
Abstract
A method is proposed for the germination of fungal-free seeds of Magnolia grandiflora as a source of tissue for in vitro experiments. A combination sequence of a 16 hour water-soak at 25Β°C, hot water (52Β°C) for 1 hour, and then surface sterilization for 1 hour in 1:1000 aqueous mercuric chloride was the best treatment. Dips in 2.5% chlorox, 95% ethyl alcohol and concentrated sulfuric acid soak for 20 minutes were unsatisfactory. If seeds are selected carefully and treated as described, 60 to 90% of the seeds will germinate aseptically within 30 days.
The temperate native terrestrial orchids are endangered species. Their propagation from seeds poses specific problems. It is well known that orchid seeds are devoid of endosperm and in nature they need microscopic fungi in a symbiotic relationship for germination. We developed a successful asymbiotic in vitro culture method for germinating seeds of several temperate orchid species and for maintaining the cultures of young plantlets. The medium used for both germination and seedling culture was a modified FAST medium. Seeds were surface-disinfested for 10 minutes in a 10% calcium hypochlorite solution. After sowing, the cultures were kept under dark condition at 10β12Β°C for 4 weeks. After that the cultures remained in the dark, but the temperature was raised to 25β26Β°C until germination occurred. Thereafter cultures required alternating seasonal temperatures: 25β26Β°C from the beginning of April to the end of September and 17β19Β°C from October to March. For the development of the young plantlets natural dispersed light and prevailing day-length was favorable. After 2 years of aseptic culture they were suitable for transfer ex vitro. Different stages of seed germination and plant development were observed using a scanning electron microscope and will be included in this presentation. Further observation of the effects of different environmental factors is currently under investigation.
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
Contribution from MIGAL. We thank Hillary Voet for her valuable assistance in the statistical analysis and Dahlia Eisenstein for her valuable technical assistance. The cost of publishing this paper was defrayed in part by the payment of page charges
Many researchers regard somatic embryogenesis as a system of choice for in vitro propagation of superior varieties of crops such as coffee, mango, datepalm, and rose. While there are advantages, commercialization has not been possible so far in coffee, mango, and rose. The work highlights some reasons for this and feasible alternatives. We have established somatic embryogenesis in four elite Indian arabica coffee genotypes. Plantlets (3500) of all the four varieties are now being field-evaluated. The cost of producing these propagules is 15 times the seedling cost at present. A major constraint is the long time (6 months) needed to reach the five-leaf stage in vitro prior to release for acclimatization. This period can be reduced to 2 months using exvitro development after the two leaf stage. There are many reports of somatic embryogenesis in mango. Results on establishing free-living plantlets have not been encouraging.We found a number of abnormalities in the shape of the somatic embryos in cv. Rumani. However, except for the βrodβ-shaped ones (that lacked cotyledonary expansion), all embryos germinated satisfactorily (75% rooting).We have encouraging results in reducing the time required to generate suitable plantlets for field acclimatization and in standardizing the procedures for grafting. Our laboratory has developed methods for ex vitro germination of mature embryos in datepalm,which yield more numbers of free-living plantlets (50%β60%) in only 3 months with an average of four leaves per plant. This compared favorably with in vitro germination that takes 6 months and produces plantlets with one or two leaves only. A novel protocol for obtaining somatic embryogenesis in rose from petal derived calli was developed by us (Murali et al., 1996). The number of embryos induced was too low for commercial application. [Murali et al., 1996. Euphytica 91:271β275].