Plant defence genes are induced in the pathogenic interaction between bean roots and Fusarium solani, but not in the symbiotic interaction with the arbuscular mycorrhizal fungus Glomus mosseae

Abstract

Plant roots enter symbiotic as well as pathogenic interactions with fungi in the rhizosphere. We studied the response of bean (Phaseolus vulgaris L. cv. Saxa) roots to infection by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe and the pathogen Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burkholder) Snyder & Hansen. In a time‐course study of the symbiotic interaction between bean roots and G. mosseae, covering all stages of mycorrhiza development, we detected little change in the expression of the defence‐related genes chitinase, β‐1,3‐glucanase and phenylalanine ammonia‐lyase compared with non‐mycorrhizal control roots. The only difference observed was a transient increase in chalcone synthase transcripts at later stages of mycorrhizal root colonization. In interactions with the pathogen, a marked induction of chitinase and phenylalanine ammonia‐lyase expression was observed at the level of both the transcripts and enzyme activities. Class I β‐1,3‐glucanase levels strongly increased at the transcript level, but there was little change in the overall β‐1,3‐glucanase enzyme activity. In the non‐host interaction between common bean and Fusarium solani (Mart.) Sacc. f. sp. pisi (Linford) Snyder & Hansen defence responses increased only slightly and transiently, if at all.

Flavonoid biosynthesis and degradation play a role in early defence responses of bilberry (Vaccinium myrtillus) against biotic stress

“…Infection of plant tissue by rhizobia and mycorrhiza can induce production of chitinases and defence proteins specific for the interaction (Pozo et al 1999;Salzer et al 2004). PR genes are produced equally, or to a less degree towards rhizobia and mycorrhiza than promoted by a pathogen (Mohr et al 1998). Endophytes typically promote stronger and faster defence responses than pathogens, characterised by production of H 2 O 2 , and elevated activity of the phenylalanine ammonia lyase (PAL) enzyme (Schulz et al 1999;Laukkanen et al 2000).…”

Multitrophic links between arbuscular mycorrhizal fungi and insect parasitoids

“…van Dam et al. (2003) point out that there are no known effects of AM fungi on induced defences in plants, as these fungi seem to suppress the defence response of their hosts (Mohr et al. 1998).…”

Arbuscular mycorrhiza in mini‐mycorrhizotrons: first contact of Medicago truncatula roots with Glomus intraradices induces chalcone synthase

“…Similarly, F. solani f. sp. pisi could not induce a defence response in the closely related P. sativum (Mohr et al. , 1998).…”

“…Our experiments showed that Mt‐chs1 is expressed at a low level also in noninoculated plants. This could have led some authors to conclude that the transcription of CHS, if at all, is only slightly enhanced (Blee & Anderson, 1996; Mohr et al. , 1998).…”