Transcriptomic analysis of Allium sativum uncovers putative genes involved in photoperiodic pathway and hormone signaling under long day and short day conditions.

Photoperiod is dominant environmental factor that controls plant growth and development. Even though research on plants response to photoperiod is significant in agriculture, molecular mechanisms of garlic in response to photoperiod remain largely unknown. In the current investigation, 3 months old garlic plants were treated with long day (LD) and short day (SD) for 10 and 20 days after treatment (DAT). Liquid chromatography-mass spectrometry (LC-MS) analysis of phytohormones exhibited that indole-3-acetic acid (IAA), zeatin riboside (ZR) and salicylic acid (SA) were observed maximum under LD at 10 DAT, whereas abscisic acid (ABA), gibberellic acid 3 (GA3), zeatin (ZT) and jasmonic acid (JA) were observed maximum under LD at 20 DAT. Transcriptome sequencing analysis was done to evaluate the transcriptional response to LD and SD. Differentially expressed genes (DEGs) were detected to have pathway enrichment. i.e., DNA binding transcription factor activity, transcription regulator activity, transferase activity, transferring hexosyl groups, and sequence specific-DNA binding activity, plant hormone signal transduction, circadian rhythm-plant, biosynthesis of amino acids, phenylpropanoid biosynthesis, and starch and sucrose metabolism. Furthermore, 28 and 40 DEGs were identified related to photoperiod and hormone signaling, respectively and their interaction in response to LD and SD were discussed in detail. Outcomes of current investigation might be useful to provide novel resources for garlic bulb formation in response to photoperiod.

Application of garlic allelochemicals improves growth and induces defense responses in eggplant (Solanum melongena) against Verticillium dahliae.

Aqueous garlic extracts (AGE) and garlic allelochemical diallyl disulfide (DADS) have been recently reported to bear bioactive properties to stimulate plant growth and development and alter defense-related physiology. We, therefore, performed a bioassay to study these chemicals as possible biostimulants for defense against Verticillium dahliae in eggplant seedlings. AGE and DADS were applied as a foliar application to the eggplants and samples were collected before and after pathogen inoculation at various intervals to analyze the defense mechanism. The obtained data revealed that with the application of AGE and DADS, the seedlings showed responses including activation of antioxidant enzymes, an abundance of chlorophyll contents, alteration of photosynthesis system, and accumulation of plant hormones compared to the control plants. Furthermore, the microscopic analysis of the AGE or DADS treated plants showed high variability in pathogen density within the root crown at 28 days post-inoculation. The low abundance of reactive oxygen species was noticed in AGE or DADS treated plants, which indicates that the plants were able to successfully encounter pathogen attacks. The AGE and DADS treated plants exhibited a lower disease severity index (32.4% and 24.8% vs 87.1% in controls), indicating successful defense against Verticillium infection. Our results were therefore among the first to address the biostimulatory effects of AGE or DADS to induce resistance in eggplant seedlings against V. dahliae and may be used to establish preparation for garlic-derived bioactive compounds to improve growth and defense responses of eggplants under-protected horticultural situations such as glasshouse or plastic tunnels system.

Allium sativum L. (Garlic) bulb enlargement as influenced by differential combinations of photoperiod and temperature.

Photoperiod and temperature are vital environmental factors that regulate plant developmental processes. However, the roles of these factors in garlic bulb enlargement are unclear. In this report, responses of garlic bulb morphology and physiology to combinations of photoperiod (light/dark: 10/14 h, 12/12 h, 14/10 h) and temperature (light/dark: 25/18 °C, 30/20 °C) were investigated. For garlic cultivar G103, bulb characteristics, phytohormones (IAA, ABA, ZT, tZR, JA), allicin and phenolic acids (p-coumaric and p-hydroxybenzoic) were highest under a photoperiod of 14 h at 30 °C. Maximum GA was observed under 14 h + 30 °C for cv. G2011-5. Maximum caffeic, ferulic and vanillic acids were detected for cv. G2011-5 at 14 h + 30 °C, 12 h + 25 °C and 14 h + 25 °C, respectively. Flavonoids (myricetin, quercetin, kaempferol and apigenin) were not detected in this trial. This is the first report describing the impact of long periods of light duration and higher temperatures on garlic morphology, phytohormones, phenolic acids and allicin content.

Changes in the Soil Microbiome in Eggplant Monoculture Revealed by High-Throughput Illumina MiSeq Sequencing as Influenced by Raw Garlic Stalk Amendment.

The incorporation of plant residues into soil can be considered a keystone sustainability factor in improving soil structure function. However, the effects of plant residue addition on the soil microbial communities involved in biochemical cycles and abiotic stress phenomena are poorly understood. In this study, experiments were conducted to evaluate the role of raw garlic stalk (RGS) amendment in avoiding monoculture-related production constraints by studying the changes in soil chemical properties and microbial community structures. RGS was applied in four different doses, namely the control (RGS0), 1% (RGS1), 3% (RGS2), and 5% (RGS3) per 100 g of soil. The RGS amendment significantly increased soil electrical conductivity (EC), N, P, K, and enzyme activity. The soil pH significantly decreased with RGS application. High-throughput Illumina MiSeq sequencing revealed significant alterations in bacterial community structures in response to RGS application. Among the 23 major taxa detected, Anaerolineaceae, Acidobacteria, and Cyanobacteria exhibited an increased abundance level. RGS2 increased some bacteria reported to be beneficial including Acidobacteria, Bacillus, and Planctomyces (by 42%, 64%, and 1% respectively). Furthermore, internal transcribed spacer (ITS) fungal regions revealed significant diversity among the different treatments, with taxa such as Chaetomium (56.2%), Acremonium (4.3%), Fusarium (4%), Aspergillus (3.4%), Sordariomycetes (3%), and Plectosphaerellaceae (2%) showing much abundance. Interestingly, Coprinellus (14%) was observed only in RGS-amended soil. RGS treatments effectively altered soil fungal community structures and reduced certain known pathogenic fungal genera, i.e., Fusarium and Acremonium. The results of the present study suggest that RGS amendment potentially affects the microbial community structures that probably affect the physiological and morphological attributes of eggplant under a plastic greenhouse vegetable cultivation system (PGVC) in monoculture.