Thymol Edible Coating Controls Postharvest Anthracnose by Regulating the Synthesis Pathway of Okra Lignin

Arthropod Pests, Nematodes, and Microbial Pathogens of Okra (Abelmoschus esculentus) and Their Management—A Review

Okra (Abelmoschus esculentus) is an important agricultural crop of the Malvaceae family, cultivated across tropical, subtropical, and warm temperate regions. However, okra production faces numerous challenges from diverse pest species, including insects, nematodes, arachnids, and mites, that significantly reduce its yield. Major economic pests include the cotton aphid, cotton spotted bollworm, Egyptian bollworm, cotton mealybug, whitefly, cotton leafhopper, cotton bollworm, two-spotted spider mite, root-knot nematode, reniform nematode, cotton leaf roller, and flea beetle. Additionally, less prevalent pests such as the blister beetle, okra stem fly, red cotton bug, cotton seed bug, cotton looper, onion thrips, green plant bug, and lesion nematode are also described. This review also addresses fungal and oomycete diseases that present high risks to okra production, including damping-off, powdery mildew, Cercospora leaf spot, gray mold, Alternaria leaf spot and pod rot, Phyllosticta leaf spot, Fusarium wilt, Verticillium wilt, collar rot, stem canker, anthracnose, and fruit rot. In addition to these fungal diseases, okra is also severely affected by several viral diseases, with the most important being okra yellow vein mosaic disease, okra enation leaf curl disease, and okra mosaic disease, which can cause significant yield losses. Moreover, okra may also suffer from bacterial diseases, with bacterial leaf spot and blight, caused primarily by Pseudomonas syringae, being the most significant. This manuscript synthesizes the current knowledge on these pests. It outlines various management techniques and strategies to expand the knowledge base of farmers and researchers, highlighting the key role of integrated pest management (IPM).

Konjac glucomannan/microcapsule of thymol edible coating reduces okra pericarp browning by regulating antioxidant activity and ROS synthesis

Okra is susceptible to browning during storage. The effects of konjac glucomannan/microcapsule of thymol edible coating (TKL) on antioxidant activity and reactive oxygen (ROS) synthesis of okra during low-temperature storage were investigated. Thymol edible coating of thymol concentration 40 mg/mL (TKL40) had a regulatory effect on okra browning. After 14 days of storage, compared with the control group, the weight loss rate of TKL was reduced by 5.26 %, the hardness was increased by 24.14 %, and the L⁎ value was increased by 31 %. Moreover, TKL40 increased the scavenging capacity of okra for DPPH and ABTS free radicals, and activated catalase and superoxide dismutase activities by promoting the accumulation of total phenolics and flavonoids. TKL40 also reduced the cell membrane damage of okra during low-temperature storage by reducing the increase of malondialdehyde and H2O2 during okra storage. Meanwhile, it delayed the increase of relative conductivity and the production of O2.-, inhibited the activity of polyphenol oxidase in the late stage, so reduced the combination of polyphenol oxidase and phenolics to reduce the browning. Therefore, TKL40 reduces okra pericarp browning by regulating antioxidant activity and ROS synthesis.

Chemical, antioxidant, and antifungal analysis of oregano and thyme essential oils from Ecuador: Effect of thyme against Lasiodiplodia theobromae and its application in banana rot

The objective of this study was to evaluate the antioxidant capacity by spectrophotometric methods, the in vitro and in vivo antifungal effect against Lasiodiplodia theobromae and the constitution of the essential oils (EO) of oregano and thyme in comparison with their commercial counterparts. The results showed by the EOs of extracted thyme (T-EO), commercial thyme (CT-EO), extracted oregano (O-EO) and commercial oregano (CO-EO), demonstrated antioxidant profiles with a radical neutralizing potential (DPPH•) of IC50: 1.11 ± 0.019; 1.08 ± 0.05; 40.56 ± 0.227 and 0.69 ± 0.004 mg/mL, respectively. They also revealed a ferric ion reducing capacity (FRAP) of 93.05 ± 0.52; 97.72 ± 0.42; 21.85 ± 0.57 and 117.24 ± 0.64 mg Eq Trolox/g. A reduction in β-carotene degradation of 65.71 ± 0.04; 51.97 ± 0.66; 43.58 ± 1.56 and 57.46 ± 1.56 %. A total phenol content (Folin-Ciocalteu) of 132.97 ± 0.77; 141.89 ± 2.56; 152.04 ± 0.10 and 25.66 ± 0.40 mg EGA/g. Chemical characterization performed by gas chromatography mass spectrometry (GC-MS) showed that the respective major components of the samples were thymol (T-EO: 45.78 %), thymol (CT-EO: 43.57 %), alloaromadendrene (O-EO: 25.17 %) and carvacrol (CO-EO: 62.06 %). Regarding antifungal activity, it was evident that at the in vitro level, both commercial EOs had a MIC of 250 ppm while the extracted thyme EO had a MIC of 500 ppm; In vivo studies demonstrated that the application of thyme EO had a behavior similar to the synthetic fungicide, slowing down rot in bananas under storage conditions. Finally, partial least squares discriminant analysis (PLS-DA) and heat maps suggest p-cymene, carvacrol, linalool, eucalyptol, 4-terpineol, (z)-β-terpineol, alkanhol, caryophyllene, β-myrcene, d-limonene, α-terpinene, α-terpineol, d-α-pinene, camphene, caryophyllene oxide, δ-cadinene, terpinolene and thymol as relevant biomarkers associated with the assessed bioactive properties demonstrating the potential of extracted essential oils for the development of a botanical biofungicide.

Formulization and characterization of guar gum and almond gum based composite coating and their application for shelf-life extension of okra (Hibiscus esculentus)

The current novel study aims was to development and characterization of gum based (guar gum: almond gum) composite formulations with or without addition of oregano essential oils to extend the shelf life of okra at ambient condition. In this study, the optimized composite of guar gum: almond gum (75:25 V/V) prepared with addition of different concentrations (0.05, 0.1 and 0.15 % (V/V) of oregano essential oils to study their physicochemical, rheological, antimicrobial and particle size & zeta potential distribution. In addition, the effects of prepared edible coatings on shelf-life of okra vegetables were also investigated by assessing their postharvest quality attributes at ambient (23 °C) storage up to 7 days storage. The results revealed, increasing concentration of essential oils in composite coating significantly increased in pH, TSS, particle size, antimicrobial (Apergillus. niger, Escherichia coli, Staphylococcus aureus) activity respectively. Furthermore, the increasing EOs improved viscosity (n) and stability of the coatings matrix. In addition, the applications of guar gum (0.25 %): almond gum (0.5 %) composite ratio (75,25) with oregano essential oils exhibited excellent properties and potential to maintain the postharvest characteristics of okra throughout the storage period. The results of this study revealed that the addition of higher concentration (0.15 %) of essential oils in composite formulation of 75 % guar gum +25 % almond gum (03) showed higher value of pH (5.45), antioxidant activity (20.87 %), particle size (899.1 nm), zeta potential (-8.6 mV), polydispersity index (50.6 %) and higher antimicrobial activity against E.coli (19 mm), S. aureus (29 mm) and A. niger (35 mm) as compared to other formulations. Therefore, the lower composite formulation (01) with lower concentration (0.05 %) of oregano essential oil was found most effective formulation to maintain the shelf life of okra for up to 4 days as compared to other treated and control okra samples at ambient temperature by retarded the weight loss (12.74 %), maintained higher firmness (0.998 N), lower respiration rate (484.32 ml Co2/kg/h) respectively on 7 days of storage. The microbial load in the okra samples treated with different guar gum: almond gum composite showed lower microbial load in terms of total plate count and yeast & mold counts as compared to control samples. Samples treated with O3 coating showed lowest TPC (0.1 × 108 cfu/g) and YMC (6.63 × 106 cfu/g) followed by O2 (0.48 × 108 cfu/g, 7.9 × 106 cfu/g) and O1 (0.78 × 108 cfu/g, 9.45 × 106 cfu/g) respectively on 6rd day of storage, overall results indicated that the application of composite coating with different concentrations of oregano essential oils were effective to maintained postharvest shelf life of okra up to 4 days at ambient condition.