The mitigation effects of exogenous melatonin on replant disease in apple

Abstract

Melatonin mediates many physiological processes in plants. The problem of apple replant disease is unsolved. Our study objectives were to evaluate the regulatory effect of melatonin on plant resistance to this challenge and investigate the preliminary mechanism by which melatonin helps alleviate the effects of this disease. Two-year-old trees of "Fuji" apple (Malus domestica), grafted onto rootstock M.26, were grown in "replant" soil for 6 months in the absence or presence of a 200 μmol/L melatonin supplement. The addition of melatonin to the soil significantly increased the rates of plant growth and net photosynthesis and chlorophyll concentrations under replant conditions. This molecule elevated the levels of K in leaves and roots and enhanced the activity of soil enzymes. Such supplementation also changed the composition of the bacterial and fungal communities in the soil. We concluded that the application of melatonin to a replant soil can protect their chloroplasts from oxidative damage and release the apple root from membrane damage, and also lead to increased soil enzyme activity and soil quality while altering the composition of bacterial and fungal communities. These changes can then promote seedling growth, stimulate photosynthesis, and elevate K levels, thereby alleviating the effects of apple replant disease.

Melatonin and Its Protective Role against Biotic Stress Impacts on Plants

“…Zhang, et al [67] demonstrated that the combined application of melatonin and ethylicin (an oomycete antifungal) has a synergistic effect that inhibits the in vitro and in vivo growth of Phytophthora nicotianae through disturbed amino acid metabolic homeostasis of this fungus. Exogenous application of melatonin in replant soil enhances apple seedling growth, raises K levels, and stimulates photosynthesis, which subsequently relieves the disorders of replant disease [68]. Similar results have been obtained in fungi such as Botrytis spp., Penicillium spp., Fusarium spp., P. nicotianae, and Alternaria spp.…”

“…Similar results have been obtained in fungi such as Botrytis spp., Penicillium spp., Fusarium spp., P. nicotianae, and Alternaria spp. [67][68][69]. Furthermore, several investigations have studied the role of endophytic rhizobacteria in the reinforcement ability of plants to produce melatonin [70,71].…”

Bacterial and fungal communities are differentially modified by melatonin in agricultural soils under abiotic stress

“…Recently Li et al, (2018) investigated the effect of exogenous melatonin application (200 μM; applied at 20 day intervals for 6 months) without abiotic stress in two soils types associated with horticultural practices (apple orchard and vegetables respectively) by sampling the subsoil region (20-30 cm depth). Bacterial compositions of melatonin-treated soil samples were shown to be similar to controls, however some genera, many unknown, shifted strongly in response to melatonin (Li et al, 2018). Ascomycota, in particular, were negatively affected by melatonin, resulting in greater establishment of Glomeromycota and Basidiomycota in fungal assemblages (Li et al, 2018).…”

“…Bacterial compositions of melatonin-treated soil samples were shown to be similar to controls, however some genera, many unknown, shifted strongly in response to melatonin (Li et al, 2018). Ascomycota, in particular, were negatively affected by melatonin, resulting in greater establishment of Glomeromycota and Basidiomycota in fungal assemblages (Li et al, 2018). It is difficult to directly compare our study with this report, however, these results are complimentary to the trends observed in our investigation and indicative of the importance of soil agricultural histories in microbial response to melatonin.…”

Seasonal Variation in the Rhizosphere and Non-Rhizosphere Microbial Community Structures and Functions of Camellia yuhsienensis Hu

“…The 16S rDNA V3-V4 region of the ribosomal RNA gene was amplified by PCR using primers 341F: 5′-CCTACGGGNGGCWGCAG-3′, 806R: 5′-GGACTACHVGGGTATCTAAT-3′. The PCR amplification of 16S r DNA proceeded, as described in Reference [ 43 ]. The ITS rDNA region of the ribosomal RNA gene was amplified by PCR using primers ITS3-KYO2 (F): 5′-GATGAAGAACGYAGYRAA-3′ and ITS4 (R): 5′-TCCTCCGCTTATTGATATGC-3′ [ 44 ].…”