This study examined a number of areas of interest to commercial growers of ginseng. Whilst these areas appear to have little in common academically, the findings have the potential to be a major contributing factor in establishing the Australian ginseng industry on a commercially sustainable footing.
The computer software program, CLIMEX, designed to assist in the prediction of suitable growing areas for new crops, was tested for applicability to ginseng. CLIMEX, relying on knowledge of current distribution in other countries was used to produce maps of potential Australian distribution of both Panax ginseng and Panax quinquefolius. As a consequence of that mapping, two limitation criteria have been identified. The winter extended cold criterion appears to limit the northern distribution of both species and dry stress appears to limit the western distribution - at least in the eastern States of Australia.
Two mathematical models have been developed in this study to provide greater local accuracy in predicting suitability of the winter extended cold criterion for ginseng. A map has been drawn of the eastern States, identifying the likely boundary to successful ginseng cultivation. The successful use of these models relies on an understanding of the temperature requirements of the dormant root.
While the study also investigated the time and temperature relationships required to overcome the annual winter dormancy of the ginseng root of both P. ginseng and P. quinquefolius, it revealed that further investigation on this character was warranted.
A time/temperature relationship was found which suggested that, provided a critical temperature was reached, the temperature and period of treatment at that temperature had little effect on the total time in dormancy. There was a marked difference in the proportion of roots emerging from dormancy. Experimental results from this study have not confirmed the accuracy of the industry belief that a ginseng root requires a minimum of 100 days at a soil temperature of less than 10°C. However, such a treatment remains the most probable extended cold requirement.
In addition, a number of physical and chemical treatments for reducing root dormancy were assessed. Gibberellic acid was found to significantly reduce time in dormancy. Potassium nitrate was also found to reduce the dormancy requirement of the root but the effect was not as marked as that of gibberellic acid.
The study also assessed seed dormancy with a view to establishing a protocol for reducing the time to germination, and increasing the success rate of germination. Dormancy has been identified as a process with a minimum of two-stages. Ginseng seed requires warming followed by chilling. Whether a third, preceding cold phase is required is uncertain.
Several chemicals were investigated to determine their effect on germination. Bleach is commonly used by ginseng growers as a surface fungicide prior to storage, transport and before planting. Soaking ginseng seed in bleach was found to have no effect on germination.
The plant growth regulator gibberellic acid, which is endogenous to ginseng, was shown to have a significant effect on reducing the need for the cold phase of dormancy. It has been established that a protocol for soaking the seeds for one hour in a commercially available gibberellic acid solution at a concentration of l,000ppm will enable maximum germination percentage within three months of receipt of seed. Before gibberellic acid can be used commercially in this context it needs to be registered for use as an agricultural chemical. This will require further research to identify an appropriate protocol for its safe use, including an appropriate withholding period.
Tissue culture was assessed as a mechanism for commercial ginseng production. The study established that both P. ginseng and P. quinquefolius were easily cultivated in vitro. In relation to establishment and increase in mass of callus tissue they showed a surprising tolerance to changes in concentration and relative composition of the culture media. They also showed tolerance to pH changes as high as ten fold, however, were less tolerant of changes in sugar concentration of the media. The plant growth regulators 2,4-D and NAA appear the only major regulators useful in the mass micropropagation of ginseng.