Interactions between the soilborne root pathogenPhytophthora nicotianae var.parasitica and the arbuscular mycorrhizal fungusGlomus mosseae in tomato plants

Abstract

In order to study the influence of Arbuscular Mycorrhiza (AM) on the development of root rot infection, tomato plants were raised with or without Glomus mosseae and/or Phytophthora nicotianae var. parasitica in a sand culture system. All plants were fed with a nutrient solution containing one of two phosphorus (P) levels, 32 #M (I P) or 96 #M (IIP), to test the consequence of enhanced P nutrition by the AM fungus on disease dynamics. Mycorrhizal plants had a similar development to that of control plants. Treatment with Phytophthora nicotianae var. parasitica resulted in a visible reduction in plant weight and in a widespread root necrosis in plants without mycorrhiza. The presence of the AM fungus decreased both weight reduction and root necrosis. The percentage reduction of adventitious root necrosis and of necrotic root apices ranged between 63 and 89% The enhancement of P nutrition increased plant development, but did not appreciably decrease disease spread. In our system, mycorrhiza increased plant resistance to P. nicotianae var. parasitica infection. Although a contribution of P nutrition by mycorrhiza cannot be excluded, other mechanisms appear to play a crucial role.Abbreviations: AM -arbuscular mycorrhizae, G-Phy--plants without G. mosseae nor P. nicotianae var. parasitica, G + Phy--plants with G. mosseae but without P. nicotianae var. parasitica, G-Phy + -plants without G. mosseae but with R nicotianae var. parasitica, G + Phy + -plants with both G. mosseae and P nicotianae var. parasitica, I P -first phosphorus level (32 #M), IIP -second phosphorus level (96/zM).

Nucleus size in the host cells of an Arbuscular Mycorrhizal system: a mathematical approach to estimate the role of ploidy and chromatin condensation

“…Early Mech) plants, inoculated with Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe (BEG 12) inoculum by Biorize (Dijon, France), and non-mycorrhizal (control) plants were grown as previously described by Trotta et al (1996) and were harvested after one month.…”

The symbiosis between Nicotiana tabacum and the endomycorrhizal fungus Funneliformis mosseae increases the plant glutathione level and decreases leaf cadmium and root arsenic contents

“…Petit Havana) were sterilized in 10% sodium hypochlorite for 10 min, carefully washed three times with sterile deionized water, and germinated for 1 week in Vitro Vent vessels (Duchefa Biochemie, Haarlem, NL), on sterile MS medium (Murashige and Skoog, 1962) provided with 1% sucrose and 1% agar. Subsequently the sterile plantlets continued to grow in the same vessels for a further 7 weeks, and were then transplanted into pots filled with sterile quartz sand, fed everyday with Long Ashton nutrient solution, pH 5.6, containing 32 mM phosphorus (in the form NaH 2 PO 4 ) (Trotta et al, 1996) washed with deionized water, and then separated into roots and leaves. Root and leaf fresh weights (FW) were taken, part of the samples were frozen in liquid nitrogen and placed at À80 C for thiol-peptide analysis; part of the root samples was conserved in 70% ethanol for mycorrhizal evaluation.…”

Apical meristems of tomato roots and their modifications induced by arbuscular mycorrhizal and soilborne pathogenic fungi

“…In A. porrum, symbiotic fungi alter the morphology, activity and size of root apices Fusconi et al, 1994) and consequently the root architecture (Berta et al, 1990). Pathogenic fungi, too, can alter the root system morphology (Larkin et al, 1995 ;Trotta et al, 1996), though their effect on the apices is unknown.…”

“…Some pots were inoculated with chopped roots of Allium porrum L. infected with Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe (BEG 12) and cultured as described in Trotta et al, 1996. One month later, nonmycorrhizal and mycorrhizal plants were inoculated with c. 10& zoospores of Phytophthora nicotianae var.…”