Biotechnology
N. Khaledi; F. Hassani
Abstract
Thyme (Thymus vulgaris L.) is rich in phenolic monoterpenes such as thymol and carvacrol. Seed-borne fungi can reduce the quality and quantity of crop and also change the amount and type of secondary metabolites in plants by affecting seed health. The aim of this study was to isolate and identify the ...
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Thyme (Thymus vulgaris L.) is rich in phenolic monoterpenes such as thymol and carvacrol. Seed-borne fungi can reduce the quality and quantity of crop and also change the amount and type of secondary metabolites in plants by affecting seed health. The aim of this study was to isolate and identify the seed-borne fungi from thyme seed samples and to evaluate the effects of seeds infection on the production and expression of genes involved in the biosynthesis pathway of thymol and carvacrol compounds. To identify seed-borne fungi of thyme seed samples collected from fields of Alborz province, sampling was done according to the criteria of the International Seed Testing Association (ISTA). The amount of thymol and carvacrol compounds was measured using high performance liquid chromatography (HPLC) and the expression of TvTPS1, DXR, CYP178, and CYP180 genes was assayed by reverse transcription polymerase chain reaction (RT-PCR). Six Alternaria brassicicola isolates were identified based on morphological and molecular characteristics. Analysis of cell wall degrading enzymes activity revealed that cellulase and pectinase were more important than xylanase and chitinase on the pathogenicity and aggressiveness of isolates. Seeds infection by A. brassicicola significantly affected vigor and seed germination indices. The findings of this study showed that the pathogenicity and aggressiveness of A. brassicicola fungal isolates can change the expression level of different genes encoding thymol and carvacrol compounds in seedlings obtained from seed pretreatments with different isolates through different mechanisms including production of extracellular enzymes resulted in increasing (isolates Ab4 and Ab5) and/or decreasing (isolates Ab1, Ab6, Ab2, and Ab3) the production and accumulation of phenolic monoterpenes in thyme seedlings. This is the first report on the identification of seed-borne fungus A. brassicicola from thyme seed samples in Iran and also the role of seeds infection on the production and expression of genes involved in the thymol and carvacrol biosynthesis pathway.
Improvement and breeding
N. Khaledi; A. Dehshiri; F. Hassani
Abstract
This study was aimed at investigating the effects of biopriming with a number of native isolates of Trichoderma harzianum on the germination and seed vigor indices of a native cumin (Cuminum cyminum L.) population. Also, the effects of extracellular enzymes produced by these isolates as elicitors on ...
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This study was aimed at investigating the effects of biopriming with a number of native isolates of Trichoderma harzianum on the germination and seed vigor indices of a native cumin (Cuminum cyminum L.) population. Also, the effects of extracellular enzymes produced by these isolates as elicitors on the production and accumulation of secondary metabolites in the seedlings obtained from bioprimed seeds were studied. Based on the results, all the T. harzianum isolates were able to produce the enzymes amylase, protease, cellulase, xylanase, chitinase, and lipase. The results also showed that the cumin seed biopriming significantly affected the germination and seed vigor indices and improved the quality and health of seeds and seedlings. In this study, the essential oil of seedlings obtained from the bioprimed seeds was extracted by water distillation and its chemical compounds were identified by GC and GC/MS. The results showed that the main compounds identified included β-pinene, ρ-cymene, limonene, γ-terpinene, terpinen-4-ol, α-terpineol, cuminaldehyde, and β-farnesene. Also, T. harzianum and the enzymes secreted by it as elicitors increased the expression of genes associated with the production and accumulation of secondary metabolites in cumin. This is the first report on the effects of seed biopriming with the native isolates of T. harzianum on the essential oil compounds of cumin seedlings. The findings of this research showed that the amount of extracellular enzymes secreted by the T. harzianum isolates is different and affects the production and accumulation of secondary metabolites in cumin.
