Influence of Nitrogen and Sulfur Fertilizers and Inoculation with Arbuscular Mycorrhizal Fungi on Yield and Pungency of Spring Onion

Abstract

A pot experiment was conducted out to investigate the yield and pungency of spring onion (Allium fistulosum L.) as affected by inoculation with arbuscular mycorrhizal (AM) fungi and addition of nitrogen (N) and sulfur (S) fertilizers. Plants were inoculated with either Glomus mosseae or Glomus intraradices or grown as uninoculated controls. Two levels of N and S were applied to the soil in factorial combinations of 50 and 250 mg N kg −1 soil and 0 and 60 mg S kg −1 soil. Plants were grown in a greenhouse for 25 weeks and then harvested. Mycorrhizal colonization resulted in increased shoot dry weight, shoot-to-root ratio, shoot length, sheath diameter, and phosphorus (P) concentrations. Shoot dry-matter yield was significantly affected by added N, but not by S. Shoot dry weight increased with increasing N supply (except for non-mycorrhizal controls without additional S fertilizer). Shoot total S concentration (TSC), enzyme-produced pyruvate (EPY), and organic sulfur concentration (OSC) in plants inoculated with Glomus mosseae were significantly lower than those of non-mycorrhizal controls, while these parameters in plants inoculated with Glomus intraradices were comparable to or higher than in the controls. Neither N nor S supply affected shoot EPY or OSC, whereas shoot TSC (except in plants inoculated with Glomus mosseae) and SO 2− 4 concentrations were usually significantly increased by S supply. In soil of high S and low P availability, mycorrhizal colonization had a profound influence on both the yield and the pungency of spring onion.

Mycorrhizal Symbiosis and Plant Reproduction

“…Mycorrhizal infection may also influence plant secondary metabolism (Guo et al 2006;Venkateswarlu et al 2008), and secondary metabolites are key molecules in the interaction between plants and their pests (Pickett et al 1999;Mayer 2004). For example, infection by of Douglas-fir by Laccaria laccata can increase resistance to fungal pathogens, possibly by inducing greater production of phenolic compounds by the host (Sylvia 1983).…”

Pungency of Spring Onion as Affected by Inoculation with Arbuscular Mycorrhizal Fungi and Sulfur Supply

“…Although AM fungalmediated growth promoting effects have been shown previously in pot experiments (Tawaraya et al, 1999;, to our knowledge the present study is the first in which experimental observation has shown that mycorrhizal colonization can have a large influence on the pungency of spring onion. Previous experiments showed that mycorrhizal fungi tended to affect the pungency of Allium cepa (Guo et al, 2006a) and Allium fistulosum (Guo et al, 2006b). However, the EPY value did not differ significantly between the mycorrhizal plants and the Table 3 Enzyme Produced Pyruvate (EPY, μ mol ml −1 ), shoot total sulfur concentration (TSC, %), root total sulfur concentration (%), shoot and root sulfur content (mg pot −1 ), and mycorrhizal S dependency (%) of spring onion EPY Shoot Root Shoot S Root S Mycorrhizal S Sulfur supply and (μ mol TSC TSC content content dependency mycorrhizal status ml a By analysis of variance; ***, P < 0.001; **, P < 0.01; *, NS, not significant.…”

“…In previous work, the effect of mycorrhizal inoculation and N and S fertilization on the pungency of spring onion grown in soil was investigated. The EPY production tended to be mediated by mycorrhizal colonization, but not by N or S supply level (Guo et al, 2006b). The aim of the present study was to investigate further the effect of mycorrhizal colonization and S supply on the pungency of spring onion in order to give more insight into the flavor regulation of the spring onion plants.…”

A 60-year journey of mycorrhizal research in China: Past, present and future directions

“…Concentrations of S and pyruvic acid were generally greater in the shoots of AM-associated onions (Allium spp.) than in non-AM onions, and inoculation of these with four Glomus species may strongly encourage a pungent flavor [143][144][145]. Improved tolerance of salt stress was found to be related to higher soluble sugar accumulation in maize roots inoculated with Glomus mosseae [138].…”