Ethylene induced nitrile and VOC synthesis by soil microbes; Improved root elongation & reduced risk of fungal infection in plants.

The scope of the project was to develop a method to induce soil microbes to inhibit fungal infection and improve root elongation. The study was randomized. Gladiolus bulbs selected for the study were visibly inspected to for viability and visible signs of infection. Two trials were conducted from Aug. 5 th – Sept. 5 th 2014 with 4 replicates per condition over a 7-d period in damp outdoor conditions in late summer. A mixed culture of plant growth promoting rhizobacteria (PGPR) were collected from soil surrounding the roots of young fruit bearing trees. Microbes were mixed with minimal media (no-carbon source), and cultured with an ethylene and used as potting soil. Bulbs planted in ethylene induced soil displayed 0% visible fungal growth, while 38% of bulbs grown in control conditions displayed some form of fungal growth and/or infection. Ethylene induced soil increased root length by 225% in bulbs in 7-d period. GC Mass Spectrophotometry data suggest ethylene may induce soil microbes to synthesize several VOCs including (ethanol, 3-methyl-1-butanol, pentanol) and esters (ethyl acetate), that may have synergistic benefits to lower the risk of fungal infection by soil mold, while nitrile compounds improve root elongation. The findings are preliminary, additional studies are required to understand the mechanism.