Arbuscular Mycorrhizal Fungi as Biofertilizers to Increase the Plant Quality of Sour-Orange Seedlings

Abstract

In addressing the agricultural challenges posed by climate change, the use of biofertilizers, derived from living organisms, promotes environmentally friendly crop cultivation, and represents an adaptive strategy for sustainable agriculture in the face of climate uncertainty. Careful selection of the arbuscular mycorrhizal fungus (AMF) would represent a crucial step in mycorrhizal inoculation, considering the varying levels of compatibility between the AMF and the host plant. This study aimed to assess the impact of two AMF species that are prevalent in citrus soils of south-eastern Spain (Rhizophagus irregularis and Funneliformis mosseae) on the Citrus aurantium seedlings’ behavior. Sour-orange plants showed a high mycorrhizal dependence regardless of the specific AMF species. Both R. irregularis and F. mosseae fungi exhibited high colonization percentages, with R. irregularis outperforming F. mosseae in root colonization. Inoculation with both AMF yielded notable growth improvements, but R. irregularis exhibited higher positive effects in the long term. The heightened P nutrition and increased chlorophyll concentration significantly enhanced the performance of AMF-inoculated plants. With F. mosseae, plants showed more pronounced improvements in P nutrition and a stronger correlation of their dry mass with P concentration; however, in general, inoculation with R. irregularis produced a higher sour-orange-plant performance. Both R. irregularis and F. mosseae fungi produced strong positive effects in sour-orange growth, which positioned them as viable biofertilizer options. These results can contribute to enhancing understanding for the development of an improved design of biofertilizers used in regions that are vulnerable to climate change, such as south-eastern Spain. This promotes a shift towards more sustainable and environmentally friendly agricultural practices by reducing dependence on chemical fertilizers.

Effects of Salinity on ‘Fino 95’ Lemon Trees Inoculated with Arbuscular Mycorrhizal Fungi

“…Another important nutrient that can be modified by AMF is P. Mycorrhizal association increases the acquisition of P by the host plant [68], and the improved growth of mycorrhizal plants in saline conditions is primarily related to a mycorrhiza-mediated enhancement of the host plant P nutrition [23,69,70]. In the present experiment, +AM plants were not fertilized with P, and we expected results to be similar to those previously found in other experiments where +AM plants had not been fertilized with P; besides that, they had high P concentrations because of the P input coming from the fungus [22,71]. All of these experiments were conducted in pots containing substrate composed by soil/sand (1:3) where, due to the high levels of CaCO 3 (19%, typical of southeastern Spain), a significant portion of the high soil P concentration (72 ppm Olsen P) could be in insoluble form.…”

“…All of these experiments were conducted in pots containing substrate composed by soil/sand (1:3) where, due to the high levels of CaCO 3 (19%, typical of southeastern Spain), a significant portion of the high soil P concentration (72 ppm Olsen P) could be in insoluble form. However, we anticipated that the fungal hyphae secretion of acid and alkaline phosphatases [42] would release and solubilize enough P to provide an adequate P nutrition throughout the experiment, as has been observed in previous experiments [22,71]. Contrary to preceding results, the concentrations of P in the roots and leaves of +AM plants were lower than those found in −AM plants (Tables 3 and 4).…”

Impact of Plant–Microbe Interactions with a Focus on Poorly Investigated Urban Ecosystems—A Review

“…In addition to the removal of pollutants, microorganisms (e.g., bacteria and fungi) may be used as biofertilizers, namely, inocula of beneficial microbes derived from the rhizosphere [119,120,131]. Rapid urbanization, with the consequent decrease in agricultural land area, biodiversity deterioration, climate change, and the excessive use of chemical fertilizers and pesticides in farming practices, have caused significant environmental damage and pose a risk to public health by affecting food security and sustainability in agriculture.…”

“…Therefore, we must face important challenges in the agricultural field to meet the nutritional requirements of the ever-increasing global population and the growing demand for healthy foods and move toward environmentally friendly practices and sustainable, climate-smart agriculture. Biofertilizers have been designed as valid alternatives to agrochemicals to optimize crop production while preserving environmental health [131,132]. Due to their plant growth-promoting traits, rhizosphere microorganisms play a crucial role in increasing plant biomass and crop yield under greenhouse and field conditions [132].…”

“…The mycorrhization of Jacaranda mimosifolia D. Don with arbuscular fungi promoted the growth of this ornamental plant under abiotic stresses in urban environments by enhancing its ability to acquire minerals [119]. Similarly, Rhizophagus irregularis and Funneliformis mosseae AMF had strong positive effects on sour orange (Citrus aurantium L.) growth [131]. Therefore, microorganisms (particularly rhizosphere microorganisms) represent a valid alternative to chemical fertilizers for improving crop production and plant growth and health while reducing the negative impact of polluting compounds on urban environments, which are generally heavily polluted and subjected to numerous stresses.…”