Cell Defense Responses Associated with Localized and Systemic Resistance to Phytophthora parasitica Induced in Tomato by an Arbuscular Mycorrhizal Fungus

Abstract

The arbuscular mycorrhizal fungus Glomus mosseae is able to confer bioprotection against Phytophthora parasitica in tomato roots. Localized and induced systemic resistance (ISR) have been demonstrated to be involved in pathogen control in mycorrhizal and nonmycorrhizal roots with a split root experimental system. Decreased pathogen development in mycorrhizal and nonmycorrhizal parts of mycorrhizal root systems is associated with accumulation of phenolics and plant cell defense responses. G. mosseae-containing cortical cells in the mycorrhizal tissues are immune to the pathogen and exhibit a localized resistance response with the formation of cell wall appositions reinforced by callose adjacent to intercellular hyphae. The systemically induced resistance in nonmycorrhizal root parts is characterized by elicitation of host wall thickenings containing non-esterified pectins and PR-1a protein in reaction to intercellular pathogen hyphae, and by the formation of callose-rich encasement material around P. parasitica hyphae that are penetrating root cells. PR-la protein is detected in the pathogen wall only in these tissues. None of these cell reactions are observed in nonmycorrhizal pathogen-infected root systems, where disease development leads to host cell death. The cellular and molecular basis of bioprotection by an arbuscular mycorrhizal fungus is discussed in relation to that induced by other nonpathogenic microorganisms.

Pre-inoculation with arbuscular mycorrhizal fungi suppresses root knot nematode (Meloidogyne incognita) on cucumber (Cucumis sativus)

“…Our results suggest that the three fungi tested can to some extent inhibit the development and reproduction of the RKN and thus may be considered to control RKN disease in cucumber. The protective effect of AM fungi may be due to systematic or local (Cordier et al 1998;de la Pena et al 2006) operating mechanisms which may mediate the physical and physiological plant response to the RKN. Alternatively, AMF may have a direct suppressive effect on nematodes as both organisms might compete for root space and feeding sites (Francl 1993).…”

Effect of Arbuscular Mycorrhizal Fungi on Growth and Development of Potato (Solanum tuberosum) Plant

“…Depending on the individual AMF and soil conditions many plant species show large positive growth response to AMF colonisation (Cordier et al, 1998). Both potato plant varieties are highly responsive to several AM Fungi which tend to associate with potato roots and later peel to improved plant growth and nutrient uptake.…”

Induced Resistance in Mycorrhizal Tomato is correlated to Concentration of Jasmonic Acid

“…Increased phenols locally induced by AM fungi were reported for some plant, but the literature on increased phenols systemically induced by AM fungi is still scarce. Cordier et al [14] found that decreased colonization by Phythophthora parasitica in mycorrhizal and non-mycorrhizal parts of mycorrhizal plants was associated with an accumulation of phenolics. Ortho-dihydric phenol level was also found to be increased in mycorrhizal plants.…”