Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2005
Publication Date: 7/5/2005
Citation: Khan, N.I., Tisserat, B., Berhow, M., Vaughn, S.F. 2005. Influence of autoclaved fungal materials on spearmint (Mentha spicata L.) growth, morphogenesis, and secondary metabolism. Journal of Chemical Ecology. 31(7):1579-1593. Interpretive Summary: Living fungal biocontrol agents have long been known to protect plants against diseases and may, in some cases, stimulate plant growth. In this study, we studied the influence of dead autoclaved fungal materials to stimulate spearmint plant growth, development, and secondary metabolism. We conducted a survey study employing several fungal species, isolates, and cellular materials such as culture filtrate, freeze dried mycelium, mycelium suspension, and spore suspension applied either as a drench or as a spray on spearmint plants. Only certain specific fungal species and isolates showed any positive effects on plant growth and morphogenesis. Best growth and morphogenesis responses were obtained employing Aspergillus sp., Penicillium sp., or T. reesei foliar sprays. Spearmint oil (carvone) levels in fungal treated plants were comparable to non-treated controls. However, total carvone levels per plant were higher in fungal treated plants because of their increased fresh weight. A vast amount of waste fungal mycelium is generated from paper pulp and enzyme production industries. Our results suggest that fungal mycelium can stimulate plant growth and may provide a commercial outlet source for industrial fungal waste products.
Technical Abstract: The influence of autoclaved fungal materials such as culture filtrate (CF), freeze dried mycelium (FDM), mycelium suspension (MS), and spore suspension (SS) on the growth, morphogenesis, and carvone production of spearmint (Mentha spicata L.) plants was studied. Fungal materials were either applied as a drench or spray on plants. Spearmint plants (cv. '294099') drenched with SS (1 x 10**8 spores/ml) of Trichoderma reesei failed to exhibit any significant differences for leaf numbers, root numbers, or shoot numbers compared to non-treated controls. However, significantly higher fresh weights and carvone levels were observed in plants drenched with T. reesei SS compared to the untreated controls (P = 0.05). Fungal materials derived from Aspergillus sp. NRRL 32534 and NRRL 363, Fusarium graminearum NRRL 23639, F. sporotrichoides NRRL 3299, Penicillium sp. NRRL 32532, and P. acculeatum NRRL 2129, Rhizopus oryzae NRRL 395, T. reesei NRRL 11460 C30 and NRRL 3652 were sprayed on spearmint foliage. F. graminearum, F. sporotorichoides, or R. oryzae failed to elicit any enhanced growth, morphogenesis, or secondary metabolism responses. Best growth and morphogenesis responses were obtained employing Aspergillus sp., Penicillium s., or T. reesei foliar sprays. For example, spearmint cv. '557807' plants sprayed with 100 mg/l FDM T. reesei isolate NRRL 11460 C30 stimulated higher fresh weights (75%), shoot numbers (39%), leaf numbers (57%), and root numbers (108%) compared to untreated plants (P=0.05). This effect was not dose dependent, since similar growth and morphogenesis responses were obtained by testing 10, 100, or 1,000 mg/l FDM concentrations. Carvone levels in fungal treated foliar sprayed plants were comparable to non-treated controls. However, total carvone levels per plant were higher in fungal treated plants because of their increased fresh weight.