Germination variation in Arabidopsis thaliana accessions under moderate osmotic and salt stresses.

. VALLEJO AJ, YANOVSKY MJ AND BOTTO JF

ANNALS OF BOTANY

OXFORD UNIV PRESS

Año: 2010 vol. 106 p. 833 - 842

0305-7364

Background Water and salt stresses are two important environmental factors that limit the germination of seeds in most ecological environments. Most studies conducted so far to address the genetic basis of the above phenomenon have used stress conditions that are much more extreme than those found in natural environments. Furthermore, although excess of ions and water restrictions have similar osmotic effects on germination, the common and divergent signaling components mediating the effects of both factors remain unknown. Methods We compared the germination of seeds under moderate solutions of NaCl (50 mM) and polyethylene glycol (PEG, -0.6Mpa) in 28 Arabidopsis thaliana accessions. Because Bayreuth (Bay) and Shadara (Sha) accessions showed contrasting sensitivity responses to both stresses, we carried out a QTL analysis using Bay x Sha recombinant inbred lines (RIL) to identify loci involved in the control of germination under mild salt and osmotic stresses. Key Results We mapped two loci associated with salt sensitivity response, named SSR1 and SSR2 QTL, and four loci for osmotic sensitivity response, named OSR1 to OSR4 QTL. The effects of SSR1 QTL on toxic salt sensitivity and the osmotic contribution of OSR1 were confirmed by heterogeneous inbred families (HIF). Whilst SSR1 QTL appeared significant under a wide range of NaCl concentrations, OSR1 QTL was a novel loci identified specifically under moderate drought stress. Interestingly OSR1 QTL  also showed pleiotropic effects on biomass accumulation in response to  dehydratation. Conclusions The regulation of germination at moderate salt and osmotic stresses involves the action of independent major loci, revealing the existence of loci specifically associated with the toxic component of salt and not just its osmotic effect. Furthermore, this work demonstrates that novel loci control germination under osmotic stress conditions simulating more realistic ecological environments found by populations of seeds in nature.