Influence of the arbuscular mycorrhizal fungus Glomus intrarradices on the saline stress physiology of Lotus glaber.

ANALÍA I. SANNAZZARO, EDGARDO ALBERTÓ, OSCAR A. RUIZ AND ANA B. MENENDEZ

Chascomús, Argentina

Taller; Taller interdisciplinario sobre aspectos genéticos, moleculares y ecofisiológicos del Lotus spp. y sus simbiontes.; 2005

INTECH - CONICET

Lotus glaber is a glycophytic, perennial legume from Europe that occurs widely in salinehabitats. Previous observations indicate the occurrence of genotypes highly tolerant tosalinity in different populations of L. glaber (Mujica and Rumi, 1997). Several workers haveshown that AM fungi protect the plant against salinity (Al-Karaki et al., 2001; Feng et al.,2002). In turn, a high diversity of AM fungal colonization patterns in roots of L. glaber wasfound in fields characterized by their high salinity (Sannazzaro et al., 2004).Our aim was to evaluate the effect of mycorrhizal colonization on growth response to saltstress in two genotypes of L. glaber differing in their tolerance to salinity. We alsohypothesized that polyamines, small organic cations that are thought to play a role in theplant responses to salt stress (Bouchereau et al., 1999; Simon-Sarkadi et al., 2002) areinvolved in such a process.The experiment consisted of a randomized block design with two factors: (1) mycorrhizaltreatments (with or without AM fungus) and (2) two salinity levels of 0 and 200 mM NaCl.L. glaber plants colonized by G. intrarradices grew better than non-AM ones, particularlyunder saline condition, where they showed higher values of net growth, shoot/root ratio,K/Na rate, and protein and chlorophyll contents. An increase in total free polyamine contentof mycorrhized L. glaber plants compared to non-mycorrhized ones, suggests that theseamines may be involved in the salt stress alleviation of this species. The increment inspermine levels in sensitive L. glaber plants grown under salt stress condition could be due tode novo synthesis from its metabolic precursors. In addition, high proline levels wereobserved under salt stress conditions in both genotypes. Our results interestingly indicate thatG. intrarradices established a more efficient symbiosis with the tolerant than with thesensitive genotype. Results suggest that the fungal symbiont could play an important