Chrysanthemum Growth Gains from Beneficial Microbial Interactions and Fertility Improvements in Soil Under Protected Cultivation

An investigation was undertaken to analyse the influence of microbial inoculants on growth and enzyme activities elicited, and soil microbiome of two varieties of Chrysanthemum morifolium Ramat, which were grown under protected mode of cultivation. Rhizosphere soil sampling at 45 and 90 DAT (days after transplanting of cuttings) revealed up to four- to five-fold enhancement in the activity of defence-, and pathogenesis-related, and antioxidant enzymes, relative to the uninoculated control. Plant growth and soil microbial parameters, especially soil microbial biomass carbon and potential nitrification exhibited significant increases over control. Available soil nitrogen concentrations showed 40%-44% increment in inoculated treatments. Scanning electron microscopy of the root tissues revealed biofilm-like aggregates and individual short bits of cyanobacterial filaments. Analyses of DGGE profiles of archaeal and bacterial communities did not show temporal variations (between 45 and 90 DAT). However, distinct influences on the number and abundance of phylotypes due to microbial inoculants were recorded. The inoculants - Cyanobacterial consortium (BF1- 4) and Anabaena sp.-Trichoderma sp. biofilm (An-Tr) were particularly promising in terms of the plant and soil related parameters, and remained distinct in the DGGE profiles generated. The effect of Trichoderma viride-Azotobacter biofilm on soil bacterial and archaeal communities was unique and distinct as a separate cluster. This study highlights that microbial inoculants exert positive effects, which are specific even to the rhizosphere soil microbiome of chrysanthemum varieties tested. Such inoculants can serve as soil fertility enhancing options in protected floriculture.