Effect of potential bioinoculants and organic manures on root-rot and wilt, growth, yield and quality of organically grown Coleus forskohlii in a semiarid tropical region of Bangalore (India)

Based on earlier results obtained in pot experiments, 2-year field experiments were conducted with five bioinoculants and neem cake under organic field conditions (with vermicompost as a nutritional supplement) to evaluate their potential to control root-rot and wilt (a complex problem involving Fusarium chlamydosporum and Ralstonia solanacearum) of the medicinal plant Coleus forskohlii. Plants treated with arbuscular mycorrhizal fungus (Glomus fasciculatum), neem cake or Pseudomonas fluorescens showed significantly increased plant height (1531%), plant spread (2533%), number of branches (6367%) and dry root (129200%) yields, and reduced disease incidence (4750%) compared to controls. Increases in yields were reflected by increases in N (5181%), P (1776%) and K (4474%) uptake. The forskolin content of the roots was found not to be affected by any of the bioinoculants, but forskolin yield (calculated) was increased significantly by treatment with G. fasciculatum (227%), neem cake (222%) or P. fluorescens (159%).