Effects of Light Quality on Colonization of Tomato Roots by AMF and Implications for Growth and Defense

Abstract

Beneficial soil microbes can enhance plant growth and defense, but the extent to which this occurs depends on the availability of resources, such as water and nutrients. However, relatively little is known about the role of light quality, which is altered during shading, resulting a low red: far-red ratio (R:FR) of light. We examined how low R:FR light influences arbuscular mycorrhizal fungus (AMF)-mediated changes in plant growth and defense using Solanum lycopersicum (tomato) and the insect herbivore Chrysodeixis chalcites. We also examined effects on third trophic level interactions with the parasitoid Cotesia marginiventris. Under low R:FR light, non-mycorrhizal plants activated the shade avoidance syndrome (SAS), resulting in enhanced biomass production. However, mycorrhizal inoculation decreased stem elongation in shaded plants, thus counteracting the plant’s SAS response to shading. Unexpectedly, activation of SAS under low R:FR light did not increase plant susceptibility to the herbivore in either non-mycorrhizal or mycorrhizal plants. AMF did not significantly affect survival or growth of caterpillars and parasitoids but suppressed herbivore-induced expression of jasmonic acid-signaled defenses genes under low R:FR light. These results highlight the context-dependency of AMF effects on plant growth and defense and the potentially adverse effects of AMF under shading.

Plant–Fungi Interactions: Where It Goes?

“…Under natural settings, many of the environmental conditions can change abruptly. Therefore, the response of fungi can also change, and subsequently could have significant ramifications for interaction between the plant fungi [ 122 ]. Changes in air temperature and moisture can affect fungal physiology and metabolism since they are most sensitive to these changes [ 123 ].…”

“…In contrast, infected plants under shaded conditions saw decreased plant growth and reproduction. This reduced plant growth is probably caused by the high C cost of the symbiosis in comparison to the available C and the inability of plants to properly offset the fungal C demand in low light [ 122 ]. On the other hand, as mycorrhizal plants decline rapidly with decreasing light intensity, P uptake by roots becomes marginal, thus leading to poor growth and development of plants [ 122 , 142 ].…”

“…This reduced plant growth is probably caused by the high C cost of the symbiosis in comparison to the available C and the inability of plants to properly offset the fungal C demand in low light [ 122 ]. On the other hand, as mycorrhizal plants decline rapidly with decreasing light intensity, P uptake by roots becomes marginal, thus leading to poor growth and development of plants [ 122 , 142 ]. In a recent study, Garnica et al [ 143 ] demonstrated the impact of light on the development of root endophyte Serendipita herbamans in knotweed ( Reynoutria spp.).…”

Effects of arbuscular mycorrhizal fungi on plant growth and herbivore infestation depend on availability of soil water and nutrients

“…Symbiotic associations between plants and AMF have been intensively studied, and a wide range of benefits from the symbiosis in terms of plant growth have been reported. These benefits include enhancement of plant uptake of water and nutrients, as well as the promotion of tolerance to environmental stresses like drought, salinity, heavy metal contamination, shade and extreme temperature ( Mathur et al., 2018 ; Evelin et al., 2019 ; Pasbani et al., 2020 ; Adeyemi et al., 2021 ; Begum et al., 2021 ; Saha et al., 2022 ). In addition to enhancing plant tolerance to abiotic challenges, AMF are also identified to play important roles in protecting plants against many types of biotic stresses, e.g.…”

Effects of plant-beneficial fungi on plant growth and herbivore resistance under contrasting fertilizer conditions

“…Examples of major biotic factors determining the plant-beneficial effects of fungal inoculation include the plant species and developmental stage (Geisen et al 2021), fungal species or strain (Raad et al 2019;Rasool et al 2021a), and interactions with other microorganisms (Alves et al 2021). Furthermore, environmental factors such as temperature (Di Lelio et al 2021), light availability (Konvalinková and Jansa 2016;Saha et al 2022) and soil characteristics (Del Valle et al 2020) can mediate the effects of plant-beneficial fungi interactions. As a result, the positive effects of plant-beneficial fungi are often unpredictable, posing an important bottleneck for wide adoption in agriculture.…”