ABSTRACT

The rubber-producing species Scorzonera tau-saghyz Lipsch et. Bosse (mountain gum) was used as a significant source of NR between 1930 and 1950 by the USSR because this perennial can accumulate up to 40% rubber in its roots on a dry weight basis. Wild stands of rubber plants were harvested and then various root metrics (length, diameter, weight) and compound contents (rubber, resin, and carbohydrates) were quantified in both nursery and field trials at multiple locations. Most of the historical data were lost, but a few rare early reports were discovered and translated by our co-authors in Kazakhstan. In this paper, these early data from different sites have been plotted and analyzed to guide modern cultivation efforts in Kazakhstan and in the United States. The use of a nitrogen, phosphate, and potassium complex fertilizer appeared most effective in increasing overall yield, promoting growth, and enhancing the content of rubber, resin, and carbohydrates in the plants. The highest rubber and the lowest resin concentrations were observed in September–October. The greatest yields of root biomass and rubber were obtained on relatively acidic, magnesium-rich soils (pH 5.35–7.45) with a mild climate (Krasnograd, Ukraine). However, S. tau-saghyz was able to perform quite well even when winter temperatures dropped to −20 °C (Poltavka, Kazakhstan). Good plant performance on the Poltavka, Krasnograd, and irrigated Almaty (Kazakhstan) sites suggests that adequate water is needed for good yield. Lack of water and higher pH both appeared to be detrimental to yield in Balashov (Russia) and nonirrigated Almaty sites.