Current Challenges and Future Opportunities for a Sustainable Utilization of Halophytes

Abstract

Increasing salinisation has significant and detrimental impacts on land, water and vegetation quality, wildlife environments, agronomy and ecosystem functioning. This is particularly true for and and semi-arid areas where high evapo-transpiration rates expose plants to further adaptive pressure. Unlike conventional crops, halophytes are plants that survive and are able to reproduce in environments (coasts, wetlands, and inland deserts) with higher salinity levels. These species, which represent about 1% of the world's flora, have evolved complex mechanisms at different levels (whole plant, cellular, and molecular) enabling them to successfully cope with these hostile conditions. There are about a billion ha of salt-affected land world wide, which are unsuitable for agriculture and may therefore provide unique opportunities for "halo-biotechnologies". Taking into account the increasing pressure on fresh water resources and considerable diversity of potentially useful halophytes, such an approach may help in the mid- and long-term to rehabilitate these marginal zones and create sustainable production systems. Agriculture on saline soils is an alternative agriculture under a range of salinity levels in groundwater, and/or soils. A precondition for its use is the economic value added. Yet, fundamental prerequisites have to be considered to ensure that this promising approach would be cost-effective and environmentally safe. It must yield economically viable crops at yields high enough to be accepted by the farmers. This should be concomitant with the development of agronomic techniques relevant for growing saline, water-irrigated crops in a sustainable manner. Most importantly, these practices should be sustainable, ecologically well-tolerated and not lead to further damage of natural environments. If applied successfully, such an approach may lead to domestication of wild, salt-tolerant plants to be used as food, forage, oilseed crops, as well as pharmaceutical or ornamental plants. Soil desalination represents also important tasks for the so called cash crop halophytes. The successful rehabilitation of saline marginal zones by introduction of halophytes largely depends on collecting reliable data on salt-tolerance limits during life cycle of the respective candidate species. In this contribution, we present an overview of new data gained under saline conditions during the last years with respect to halophytes of interest and discuss their likely implications at applied level.