5-Aminolevulinic Acid and Soil Fertility Enhance the Resistance of Rosemary to Alternaria dauci and Rhizoctonia solani and Modulate Plant Biochemistry.

Hosam O. Elansary,Fahed A. Al-Mana,Diaa O. El-Ansary

doi:10.3390/plants8120585

Hosam O. Elansary, Fahed A. Al-Mana + Show 1 more

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https://doi.org/10.3390/plants8120585

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Abstract

Fungal infection of horticultural and cereal crops by Alternaria dauci and Rhizoctonia solani represents an important biotic stress that could be alleviated by application of 5-aminolevulinic acid (ALA) to fertile and poor soils. Therefore, in this study, the morphological, physiological, biochemical, and genetic effects of ALA application (eight weekly applications at 3–10 ppm) to A. dauci- and R. solani-infected Salvia rosmarinus (rosemary) in fertile and poor soils were investigated. ALA-treated plants produced the longest and highest number of branches and had higher fresh and dry weights. There were increases in the major essential oil constituents (1,8-cineole, linalool, camphor, and borneol), as shown by Gas chromatography–mass spectrometry (GC-MS); higher antioxidant activities in DPPH and β-carotene-bleaching assays; upregulated superoxide dismutase (SOD) and catalase (CAT) antioxidant enzyme activities; increased total phenolics, chlorophyll, soluble sugars, and proline; increased gas exchange parameters; enhanced leaf water potential and relative water content (RWC); and upregulated expression of DREB2 and ERF3 (stress-related genes) and FeSOD, Cu/ZnSOD, and MnSOD (antioxidant genes). Several mechanisms were involved, including stress tolerance, antioxidative, and transcription regulation mechanisms. Furthermore, ALA performance was increased in higher-quality soils with higher nutrient content. This study demonstrated the novel application of ALA as a biotic stress ameliorant with enhanced performance in fertile soils.

Highlights

Plants infected with A. dauci/R. solani and treated with high doses of aminolevulinic acid (ALA) (5 and 10 ppm) produced the longest and highest number of branches under different soil mixes
The fresh and dry weights were the highest in infected and healthy plants treated with high doses of ALA
Plants infected with A. dauci/R. solani and treated with ALA showed higher values of total phenolics compared to ALA-untreated plants

Summary

Introduction

Fungal infection of horticultural and cereal crops by Alternaria dauci and Rhizoctonia solani represents an important biotic stress that could be alleviated by application of 5-aminolevulinic acid (ALA) to fertile and poor soils. This study demonstrated the novel application of ALA as a biotic stress ameliorant with enhanced performance in fertile soils. The effects of ALA as a stress ameliorant during biotic stress conditions have not yet been explored. Alternaria dauci (Pleosporaceae) is a common plant pathogen that infects most horticultural crop leaves and causes water-soaked leaf spot, yellowing of leaves, and leaf death. It can cause seedling damping-off, seed stalk blight, and infection of the inflorescence.

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