2015_03 A Rice Mutant Keeps Cool Under Stress

During the last century, the Green Revolution has preserved the global population from hunger (the fact that hunger still exists on this planet, is a political, not an agricultural problem). In addition to mineral fertilisers, chemical plant protection, and the use of machines, it has been the progress in breeding that allowed to multiply yields although area did not increase. This intensivity claimed its price, though. Especially in dry regions, inappropriate irrigation has made soils progressively salty (transpiration of water leaves salty residues). The agriculture of the future has to become more sustainable and this requires a more careful use of the precious resource water. To breed plants that consume less water and also can cope with salty soils, has therefore shifted in the focus of global research. Rice as most important staple food is of central interest in this context. In frame of the German-Egypt cooperation project Desertcereals, funded by the Federal Ministry of Education and Research, we investigate, how rice responds to salt and drought stress. To our surprise, we found that mutants we had developed affected in the synthesis of the central stress hormone jasmonic acid (a kind of plant version for adrenalin) performed superior to normal, non-mutated rice plants. In the search for an explanation we discovered that a precursor of jasmonic acid, OPDA, can cause all sort of damage, when normal plants are challenged by stress. Especially the oxidative equilibrium is messed up leading to an excess of so called reactive oxygen species. The mutants cannot synthetise OPDA and therefore remain “cool” even under stress. Of course it does not make sense to use these mutants for agriculture – the lack of jasmonic acid has also negative impact (for instance a strong reduction in fertility) – but we can now search for alternative strategies to contain OPDA and thus to improve plant performance under salt and drought stress. Our strategy is rather to use molecular breeding, whereby wild relatives of rice, old cultivars or landraces are searched for favourable variants of the relevant genes. Then these variants are introduced by natural crossing into the plant of interest. By means of the molecular information it is possible to identify in the offspring of the cross already in the seedling stage those individuals that are most favourable for the next breeding step. In contrast to traditional breeding, where only time consuming field trials will tell this, it is possible to advance more precisely and therefore more rapidly. In contrast to genetic engineering, no introduction of foreign DNA is required.

Publication

113. Hazman M, Hause B, Eiche E, Nick P, Riemann M (2015) Increased tolerance to salt stress in OPDA-deficient rice ALLENE OXIDE CYCLASE mutants is linked to an increased ROS-scavenging activity. J Exp Bot 66, 3339-3352 - pdf