Diverse Response of Five Ornamental Plant Species to Mixed Indigenous and Single Isolate Arbuscular-Mycorrhizal Inocula in Marginal Soil Amended with Organic Matter

Abstract

Five ornamental plant species, Petunia hybrida, Tegetes erecta, Callistephus chinensis, Papaver rhoeas, and Dianthus caryophyllus were inoculated with a consortium of indigenous arbuscular mycorrhizal (AM) fungi (Mi) and a single culture of Glomus intraradices (Gi) in non-sterile, P-deficient sandy loam soil amended with organic matter under field conditions. Mycorrhizal inoculation increased flowering only in C. chinensis, whereas in P. hybrida and T. erecta fewer flowers were recorded in AM-inoculated plants. Total number of flowers in AM-inoculated plants increased by a maximum of 39% in C. chinensis over uninoculated controls. AM colonization and propagule density were found to vary with host and type of AM culture used. Maximum AM colonization was recorded in T. erecta (87.9%) and P. hybrida (85.5%) when inoculated with Mi or 73.6% and 75%, respectively, when inoculated with Gi. The highest AM inoculum production was also recorded in these two hosts with an up to 200-fold increase in the number of infectious propagules at harvest. The smaller number of flowers in P. hybrida and T. erecta was attributed to heavy root colonization coupled with production of large numbers of spores, perhaps indicating the possibility of a fungal carbon drain. This study has the potential to enhance the production of ornamental crops, particularly in nutrient-deficient soils using biologically-based farming systems. Also, a buildup of the mycorrhizal inoculum in soil amended with organic matter during the cropping of these ornamental hosts could be useful in producing AM fungal inoculum for large-scale applications and for decreasing inoculum costs.