Unravelling the synergistic effects of arbuscular mycorrhizal fungi and vermicompost on improving plant growth,nutrient absorption, and secondary metabolite production in ginger (Zingiber officinale Rosc.)
Frontiers
- 1ICAR-Indian Institute of Spices Research, Kozhikode, India
- 2ICAR-IISR Regional Station, Appangala, Kozhikode, Karnataka, India
The present research explored the impact of varying concentrations of arbuscular mycorrhizal (AM) fungus inoculum and vermicompost on the growth, nutrient absorption, photosynthetic gas exchange, and quality parameters of ginger over a 2-year period in field conditions. In this study, the combination of 50 g each of AM and vermicompost increased plant height, number of tillers, and rhizome yield compared to the control. However, higher dry biomass (61 g) was observed with the combination of 75 g of each amendment. As expected, the application of arbuscular mycorrhizae (AM) positively affects spore count and mycorrhizal dependency percentage ranging from 58 to 70.5 spores per 50 g substrate and 19–36%, respectively. The combined use of vermicompost and AM led to a lower disease incidence of 10.5% in treatments with 25 g of each amendment and 10.1% in treatments with 50 g of each. Nutrient accumulations, particularly phosphorus (P), iron (Fe), and zinc (Zn), exhibited greater levels in ginger plants treated with vermicompost and arbuscular mycorrhizal (AM) inoculation, compared to uninoculated ginger rhizomes. The plants treated with AM and vermicompost increased the biomass accumulation by increasing the stomatal conductance and photosynthetic rate of leaves. AM and vermicompost improved ginger rhizome quality, increasing phenols by 37.8%, flavonoids by 35.7%, and essential oil by 29% compared to the control. The analysis revealed that the total flavonoid content was significantly higher in AM-treated samples compared to the control. However, the phenol content did not exhibit statistical significance across the treatments. Regarding essential oil (EO) content, our experiment highlighted that treatments with AM and vermicompost have consistently yielded higher EO content compared to other treatments. In contrast, there was no discernible trend in the fiber content with the application of AM and vermicompost amendments. PCA and correlation analyses revealed a positive influence on plant growth, nutrient absorption, and quality parameters, except for the incidence of diseases in ginger. Overall, our study finds that the concurrent use of vermicompost and arbuscular mycorrhizae (AM) makes a substantial contribution to the growth, nutrient uptake, photosynthetic, and quality parameters of ginger.
1 Introduction
Ginger (Zingiber officinale Rosc.) is a medicinal herb belonging to the family of Zingiberaceae. It is mainly found in tropical regions, including India, China, Indonesia, and Nigeria. The rhizome is rich in phytochemicals such as zingiberene, α-curcumin, gingerols, and shogaols, which are the primary bioactive compounds in ginger supplements. These bioactive compounds exhibit a broad spectrum of biological activities, including anti-inflammatory, antioxidant, anticancer, antimicrobial, gastroprotective, and cardioprotective effects. These properties make ginger a valuable component in traditional and modern medicine for the prevention and treatment of various diseases (Ravindran et al., 1994). Ginger cultivation is fraught with challenges that significantly impact its production and yield. Insect pests such as shoot borers, rhizome scales, and aphids pose a direct threat to plant health. Pathogenic diseases, particularly bacterial wilt, soft rot, Fusarium yellows, and Pythium rhizome rot, can cause severe crop losses. In addition, non-pathogenic factors such as nutrient deficiencies, water stress, and soil pH imbalances further complicate ginger cultivation. Effective management strategies, including integrated pest management, proper disease control, and optimal cultivation practices, are essential to mitigate these challenges and ensure successful ginger production (Prasath et al., 2014; Bhai et al., 2019).
The increasing demand for organic products underscores the necessity of transitioning ginger production toward organic farming methods (Marsh et al., 2021). Conventional agricultural practices, while effective in boosting short-term yields, lead to soil degradation, nutrient imbalance, and environmental pollution (Igiehon and Babalola, 2018). In contrast, organic farming promotes sustainable practices that enhance soil health, conserve natural resources, and produce healthier products. By adopting organic methods, ginger farmers can contribute to a more sustainable and environmentally friendly agricultural system, meeting consumer demand while ensuring the long-term viability of their farming operations.
Various methods have been explored to decrease reliance on synthetic fertilizers in agroecosystems, with biostimulants emerging as a promising solution for promoting sustainability (Zhang et al., 2023; Xu et al., 2024). Biostimulants play a crucial role in assisting agroecosystems in managing environmental stress by enhancing the absorption of vital nutrients and plant-water balance, improving photosynthesis, and consequently contributing to the production of high-quality agricultural products (Hu et al., 2022; Li et al., 2022). As research and development in this field continue, biostimulants are likely to play an increasingly vital role in sustainable agriculture, helping to meet the growing demand for food while preserving natural resources and protecting the environment. Arbuscular mycorrhizae are a widely recognized biostimulant that can provide numerous benefits to plants and function not only as biofertilizers but also as bioprotectors and bioregulators, enhancing overall plant health and productivity through symbiosis.
In addition, this fungus can penetrate the root cortical cells and form specific haustoria-like structures termed arbuscules. These structures act as mediators for exchanging metabolites among the fungi and the host cytoplasm (Begum et al., 2019). Arbuscular mycorrhizae contribute not only to the breakdown of soil organic matter but also play a pivotal role in the plant’s ability to sequester atmospheric carbon dioxide (Qiu et al., 2023; Wang et al., 2024). This is achieved through the sink effect and facilitation of the transfer of photosynthates from aboveground organs to the roots. This function is crucial in enhancing the physical characteristics of soil like aggregation and assisting the plant in acquiring nutrients and water from the soil (Sharda and Koide, 2010; Wu et al., 2011; Khan et al., 2020). AM fungi have the capacity to influence the rhizosphere environment, potentially enhancing the production of plant metabolites (Falcao et al., 2024).
The use of bio-organic compounds provides a viable option for enhancing soil physicochemical properties, plant growth, and yield. Applying compost can improve the stability and physical characteristics of soil by augmenting organic matter, overall porosity, hydraulic conductivity, formation of aggregates, and the capacity to retain water. These modifications can result in shifts in the soil microbiome, ultimately enhancing plants’ ability to withstand abiotic stresses (Benaffari et al., 2022). Employing beneficial microbes along with compost is recognized as a vital and efficient strategy for enhancing nutrient utilization efficiency in less-than-ideal conditions. Co-amending soils with compost and microbial inocula can often result in a synergistic effect on plant growth. Vermicompost contains humic acid, which can promote spore production and hyphal growth in mycorrhizal fungi. The application of a small amount of compost together with AM inoculation can have a symbiotic effect, enhancing plant growth and phosphorus and zinc uptake. The substantial microbial diversity and nutrient richness present in compost and vermicompost can collaboratively contribute to the growth of AM fungi (Cavagnaro, 2014). Numerous horticultural crops, including bananas, potatoes, grapevine, apples, strawberries, artichokes, melons, and chilies, have stated the positive growth parameters as a result of AM inoculation (Schellenbaum et al., 1991; Vosátka and Gryndler, 2000; Borkowska, 2002; Declerck et al., 2002; Locatelli and Lovato, 2002; Fortunato et al., 2005; Benkebboura et al., 2024; Pereira et al., 2024). While Taber and Trappe (1982) were the first to investigate the presence of AM in rhizomes of ginger (Z. officinale) grown in Fiji and Hawaii, the impact and underlying mechanism of AM fungi, in conjunction with compost, on improving the growth of ginger, are still not fully understood. Arbuscular mycorrhizal fungi elevate photosynthetic gas exchange and augment water absorption by orchestrating intricate communication processes between the host and the fungus (Birhane et al., 2012). The addition of organic manure with AM fungi improved the soil respiration and other photosynthetic parameters in Lettuce (Chatzistathis et al., 2024). In addition, Govindjee (1995) reported that AM fungi enhanced photosynthesis through changes in chlorophyll fluorescence (Fv/Fm). Available information on the mechanisms of AM associated with photosynthetic light use is limited.
In this study, AM fungi (Rhizophagus sp.) with or without compost were tested on ginger plants under field conditions for 2 years. Previous research has demonstrated the positive effects of both AM fungi and vermicompost on plant growth and yield individually. However, limited studies have investigated the combined effects of these biostimulants on ginger plants under field conditions. Considering the synergistic potential of AM fungi and compost, it is hypothesized that their combined application will lead to improvements in ginger growth and yield compared to their individual application or absence thereof. With this hypothesis, we aimed (a) to evaluate the impact of AM fungi with vermicompost application on the plant growth, nutrient uptake, and disease incidence of ginger and (b) to assess the influence of AM fungi with vermicompost application on physiological measurements and quality parameters of ginger.