Benefit and cost analysis and phosphorus efficiency of VA mycorrhizal fungi colonizations with sorghum (Sorghum bicolor) genotypes grown at varied phosphorus levels

Abstract

Sorghum [Sorghum bicolor (L.) Moench] was grown in a greenhouse in a low P (3.6mgkg -1) soil (Typic Argiudolls) inoculated with the vesicular-arbuscular mycorrhizal fungi (VMAF) Glomus fasciculatum and P added at 0, 12.5, 25.0, and 37.5 mgkg -1 soil to determine the effects of VAMF-root associations on plant growth, benefit and cost analysis, and P efficiency (dry matter produced/unit P absorbed). Root colonization with VAMF and shoot growth enhancements decreased with increased soil P applications. Mycorrhizal plants were less P efficient than nonmycorrhizal plants. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants were considered the benefit derived by plants from VAMF-root associations. Shoot dry matter differences between mycorrhizal and nonmycorrhizal plants with similar P concentrations were considered the costs paid by plants for VAMF-root associations. Values of benefit and cost analysis for VAMF-root associations were highest when soil P was lowest and decreased with increasing P applications. Genotypic differences for calculated costs were pronounced, but not benefits. Benefit and cost analysis may be helpful to evaluate host plant genotypes and VAMF species to optimize efficiencies of VAMF symbiosis in different soil environments.

Occurrence of arbuscular mycorrhizal fungi in different cropping systems at Cochabamba, Bolivia (Research Note)

“…Spore densities of different cropping systems seemed not to correlate with differences in soil P which varied considerably, from 4 to 45 mg P g soil -1 . This result disagrees with the wellknown fact that increasing amounts of phosphorus has a negative impact on mycorrhiza (Antunes and Cardoso 1991, Arias et al 1991, Bolan 1991, Fairchild and Miller 1990, Hung et al 1990, Raju et al 1990). Mårtensson and Carlgren (1993) Vestberg, M. et al Arbuscular mycorrhizal fungi in Bolivia found that the number of mycorrhizal spores decreased rapidly over time with increasing annual additions of a soluble phosphorus fertilizer.…”

A comparison of arbuscular and ectomycorrhizal Eucalyptus coccifera: growth response, phosphorus uptake efficiency and external hyphal production

“…Pearson & Jakobsen (1993) compared the efficiency of three AM fungi by measuring hyphal "%C use per unit $#P transported and below-ground "%C use per unit $#P transported. Both Tinker et al (1994) with ECM willow and Raju et al (1990) with AM sorghum calculated costs and benefits to the mycorrhizal plant in terms of C. Tinker et al (1994) determined that ECM willow converted 85 % of the extra C fixed into shoot biomass ( l C-use efficiency). Raju et al (1990) found that in a low-P soil, the percentage benefit of arbuscular mycorrhizas to the sorghum averaged 84 %, but the approach in this experiment was totally different and more related to the concepts suggested by Stribley, Tinker & Snellgrove (1980).…”

Influência da inoculação de fungos micorrízicos arbusculares, da acidez do solo e de fontes de fósforo no crescimento do milho

“…A interação entre FMA e P em muitos vegetais importantes agronomicamente tem sido amplamente investigada (Raju et al 1990;Silva e Siqueira, 1991;Weber e Amorim, 1994), todos eles verificando maior absorção de P.…”