THE MICROPROPAGATION OF ROBINIA PSEUDOACACIA L. FOR STUDYING THE ROBINA: RHIZOBIUM SYMBIOSIS (BLACK LOCUST)
Abstract
In the first phase of this research, a micropropagation system was developed for black locust (Robinia pseudoacacia L.). Ontogenetic age of the donor plant and the time of year in which the nodal tissue was collected had a significant effect on the success of microculture establishment. Axillary shoot proliferation stabilized after the fourth subculture. Microcultures growing on Lloyd and McCown's Woody Plant Medium (WPM) supplemented with either 4 or 8 (mu)M 6-benzylaminopurine (BA) exhibited the highest proliferation rate of at least ten new shoots per microculture every four weeks. Response surface analysis suggested that shoot proliferation could be increased by lowering the carbon:nitrogen ratio. Further analysis revealed that at low levels of phosphorus, shoot proliferation could be increased by adjusting the level of BA to 6 (mu)M. Axillary shoot propagules of any subculture age can be rooted in vitro on WPM that contains no auxin. The addition of napthaleneacetic acid to the medium inhibited rooting. But, increasing the sucrose concentration significantly enhanced root development. Ex vitro rooting of shoot propagules was only 30 percent that of in vitro rooting. Rooted plantlets were removed from their in vitro environs and successfully acclimated to greenhouse conditions by subjecting them to an intermittent fog for 15 days. In the second phase of the project, micropropagated plantlets of five host genotypes were inoculated in the greenhouse with two strains of Rhizobium to investigate the Robinia:Rhizobium symbiosis. Lack of a significant host x strain interaction for the response variables measured suggested that either the isolines or the strains have a common ancestry. It was speculated that some of the donor plants had their maternal parent in common. Differences among the isolines in terms of nitrogenase activity and photosynthetic rate indicated that some of the isolines were inefficient in fixing dinitrogen. However, no significant difference existed among the isolines with respect to either nitrogen or phosphorus concentrations in the leaf, stem, root, or nodule tissue. In vitro studies were initiated to investigate the infection process, but successful infections were not observed.
Degree
Ph.D.
Subject Area
Forestry
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