NUTRITIONAL COMPONENTS AND NITROGEN FIXATION IN SEABUCKTHORN (HIPPOPHAE RHAMNOIDES L.)

Seabuckthorn (Hippophae rhamnoides L.) is an underutilized plant, except in China and some European countries where it is comparatively popular. Seabuckthorn is a small fruit tree in the family Elaeagnaceae that originated in Central Asia. This species offers many advantages in terms of nutrition, health and environmental sustainability due to its vitamin-rich fruit and its use of symbiotic nitrogen fixation. It also offers advantages in terms of food security and income generation because it is stress-tolerant and can be used in processed products. We compared the nutritional composition of the fruit produced by two subspecies of seabuckthorn, H. rhamnoides ssp. mongolica and ssp. rhamnoides. The mature fruit of both subspecies contained high levels of beta-carotene (provitamin A) and alpha-tocopherol (vitamin E); however, the amounts of beta-carotene and alpha-tocopherol were greater in the fruit of ssp. mongolica than in that of ssp. rhamnoides. Seabuckthorn fruit also contained high levels of L-ascorbic acid (vitamin C). The levels of sugars and acids known to be important in fruit flavor were also measured in both subspecies. We also analyzed symbiotic nitrogen fixation and stress tolerance in the plants, which may facilitate extensive sustainable cultivation. Seabuckthorn is useful for the greening of non-arable land and deserts. Seabuckthorn root nodules showed high levels of nitrogen-fixation activity, similar to that seen in Rhizobium-legume root nodules. Even under nitrogen-free conditions, seabuckthorn plants with root nodules grew normally. The morphology and 16S ribosomal DNA sequence of the root nodules indicated that the nodules were formed by Frankia, which belongs to the Elaeagnus group. Finally, seabuckthorn exhibited tolerance to drought and high temperature stress. Our results indicate that small actinorhizal fruit trees like seabuckthorn may be used to ensure food security and sustainable production. Thus, further characterization and the introduction of appropriate small actinorhizal fruit trees should be pursued.