“Novel Funnel Bottle Approach to Harness Rhizofungal Hormones and Effect of Volatile Organic Compounds on Finger Millet Growth Under Salinity Stress”
摘要
Soil salinity significantly hinders crop yield, presenting a substantial challenge for global agriculture. This study aimed to address this issue by evaluating the effectiveness of two plant growth-promoting fungi (PGPF), Trichoderma harzianum JUSPF-1 and T. reesei JUSPF-110, in improving the tolerance of finger millet seedlings under NaCl stress. An investigation was done on siderophore production. Phosphate solubilization potential was assessed under optimized conditions. The hormones and volatile organic compounds (VOCs) emitted by these PGPF isolates were detected using LC–MS/MS and GC–MS. The influence of fungal hormones was assessed using a novel funnel bottle bioassay to analyze root architecture and morphology of finger millet seedlings across NaCl concentrations ranging from 0, 100, 200, 300, to 400 mM NaCl concentrations. Additionally, the effect of fungal VOCs was evaluated using a Petri dish bioassay at 0 and 400 mM NaCl concentrations. Further, a greenhouse study validated the physio-biochemical parameters (total chlorophyll, electrolyte leakage, SA, IAA, proline) and mineral composition of control and treated finger millet seedlings exposed to NaCl. Our findings indicate that T. harzianum and T. reesei could withstand NaCl concentrations up to 800 mM. LC–MS/MS analysis identified fifteen phytohormones in each isolate, including IAA, SA, cis-jasmone, GA4, and epibrassinolide. GC–MS analysis detected 182 VOCs together, with significant compounds being 1-Nonadecene, 1-Eicosene, 6-Pentyl-2H-pyran-2-one, DL-tryptophan, N-glycyl, and 1-Triacontanol. The results of the funnel bottle bioassay revealed a substantial enhancement in the shoot length and root architecture of finger millet seedlings under varying NaCl regimes (0 to 400 mM). Similarly, the Petri plate bioassay exhibited the effectiveness of fungal VOC in promoting the shoot and root length of finger millet under 0 and 400 mM NaCl concentration. Conversely, the untreated seedlings subjected to 400 mM NaCl stress showed significant reductions in growth parameters, as observed in both the bioassays. Greenhouse experiments confirmed the efficacy of the fungal treatments in enhancing seedling tolerance to salinity stress. This was evidenced by increased levels of endogenous hormones such as IAA (67.6 and 123.5%), SA (112.4 and 135.0%), total chlorophyll (44.6 and 69.8%), and proline (91.4 and 151.3%), along with decreased electrolyte leakage (30.6 and 45.4%) in T. harzianum and T. reesei respectively, compared to control. Treated seedlings also exhibited reduced Na+ levels and maintained favorable Na+/K+ and Na+/Ca2+ ratios. Therefore, this study elucidates the efficacy of T. harzianum JUSPF-1 and T. reesei JUSPF-110 in enhancing salinity resilience in finger millet, highlighting the significant role of fungal hormones, VOCs, and their contributions to overall plant health. This novel funnel bottle and VOC plate bioassays used in this study are efficient, convenient, and cost-effective in understanding the plant–microbe interactions. The results of this study offer a promising biotechnological strategy to mitigate the deleterious effects of NaCl-induced stress, providing a potentially sustainable approach for improving crop resilience in salt-affected soils.
Graphical AbstractGraphical representation showing the effect of fungal hormones and VOCs on finger millet growth under salinity stress