Carrot (Daucus carota L.) production is frequently threatened by southern blight disease caused by the soil-borne necrotrophic fungus Athelia rolfsii. Sustainable strategies to control this pathogen remain limited. In this study, we examined pathogen-induced chemical defenses in wild carrot germplasm and evaluated their antifungal relevance. Volatile metabolite profiling of four wild carrot accessions using headspace SPME-GC-MS revealed strong metabolic shifts following fungal infection. The responses included induction of monoterpenes, sesquiterpenes, fatty-acid-derived volatiles, polyacetylenes, and particularly phenylpropene compounds. Among these, apiole, myristicin, elemicin, and β-asarone accumulated specifically after infection and showed accession-dependent induction patterns. In vitro assays demonstrated that these phenylpropenes inhibit A. rolfsii mycelial growth in a dose-dependent manner, with β-asarone displaying the strongest antifungal activity. Temporal growth analyses further revealed compound-specific suppression dynamics that interfere with fungal expansion over time. Comparative profiling of cultivated carrots showed that red carrot cultivars retain inducible phenylpropene biosynthetic network, whereas widely grown orange cultivars lack this response and are highly susceptible to infection. Importantly, exogenous application of β-asarone at physiological concentrations significantly reduced fungal proliferation and disease severity in infected orange carrots. These findings identify volatile phenylpropenes as key chemical defenses in carrot-fungus interactions and highlight wild germplasm as a valuable reservoir of antifungal metabolites. The results also provide a mechanistic basis for enhancing resistance in carrot cultivars through breeding, metabolic engineering, or biomimetic crop protection strategies.

Phelipanche aegyptiaca is a root parasitic plant that causes significant yield losses in many crops, including carrots (Daucus carota). This study investigates the resistance mechanisms of two wild carrot accessions, PI 21793 (Daucus glaber) and PI 341902 (Daucus littoralis), against P. aegyptiaca compared to a cultivated carrot (P0114; D. carota). Wild carrots induced lower germination rates of P. aegyptiaca seeds and fewer successful tubercles, indicating both pre-attachment and partial post-attachment resistance mechanisms. Strigolactone analysis revealed significant quantitative differences between cultivated and wild carrots. While cultivated carrots exuded high levels of two strigolactones, one of which was putatively identified as the non-canonical strigolactone, 4-oxo-methyl-carlalactone, wild carrots released lower amounts of these compounds. Supplementation with the artificial strigolactone analog GR24 increased germination in P. aegyptiaca inoculated on wild carrots, suggesting that strigolactone deficiency and possibly altered composition are key pre-attachment resistance mechanisms. However, higher germination resulted in no significant improvement in tubercle development on wild carrots. Parasite seedlings showed necrosis-like symptoms at their attachment sites on wild carrot roots, indicating an additional post-attachment resistance mechanism. These findings provide new insights into strigolactone-mediated host resistance and highlight the potential of wild carrot accessions to contribute to the development of resistant cultivars against parasitic plants.

Terpenes are specialized metabolites widely distributed across life, including plants, bacteria, fungi, and insects, where they play diverse ecological and physiological roles. In plants, they contribute to defense, reproduction, and interactions with the environment. Styrax officinalis L. (Styracaceae) is an evergreen-deciduous tree or shrub that produces diverse specialized metabolites, including volatile terpenes of ecological and industrial importance. We used transcriptomic, metabolomic, and biochemical analyses to study S. officinalis, revealing the genetic and enzymatic mechanisms underlying terpene biosynthesis. RNA-seq analysis identified seven terpene synthases (StyTPS1-StyTPS7) and one putative acyclic terpene utilization protein (StyACTS). These genes were cloned, and their functions were experimentally confirmed. Transcript profiling revealed tissue-specific expression of StyTPS1 in flowers, StyTPS2-StyTPS5 in young leaves, and StyTPS6-StyTPS7 in mature leaves. Recombinant proteins with C-terminal His-tags were assayed using geranyl pyrophosphate (GPP), farnesyl pyrophosphate (FPP), and geranylgeranyl pyrophosphate (GGPP). Most TPS enzymes primarily produce acyclic monoterpenes, such as nerol (1). StyTPS3 and StyTPS4 showed substrate promiscuity, forming multiple mono- and sesquiterpenes. StyTPS5 produced defense-related sesquiterpenes, including (Z,E)-α-farnesene (2) and (E)-β-farnesene (3). StyTPS6 catalyzed the formation of diterpenes, including geranyllinalool (4), from GGPP. StyACTS produced linalool (5) and (Z)-nerolidol (6), representing novel functional terpene synthase-like activity in the plant system. The mono-, sesqui-, and diterpene products of StyTPS highlight substantial catalytic plasticity and reflect the evolutionary and ecological fitness of Styrax. These findings provide the first detailed functional map of terpene metabolism in S. officinalis and offer insights into terpene diversity, ecological roles, and biotechnological potential.

Plant volatile organic compounds (VOCs) play crucial roles in mediating plant-environment interactions, including pest attraction and deterrence, as well as attracting pollinators and deterring herbivores. The Mediterranean fruit fly (medfly) is a significant pest in fruit crops, requiring precise monitoring to optimize control measures. Our study investigates the differences in VOC profiles between identified “hot spot” areas within orchards where medfly populations tend to concentrate, and “cold spots,” where infestations are less frequent. Using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC–MS), we found that hot spots exhibited distinct VOC profiles, particularly an increase in compounds such as (E)-2-hexenal, (Z)-2-hexanol, (E,E)-2,4-hexadienal, and (E)-2-hexenyl acetate, which are known medfly attractants. These findings suggest that variations in orchard VOC emissions may provide a means of identifying regions at higher risk of infestation, thereby allowing for targeted pest management strategies. This study offers insights into VOC-mediated pest attraction and highlights the potential for refining monitoring systems based on spatial chemical variations in orchards.

The Mediterranean fruit fly (medfly, Ceratitis capitata [Wiedemann]) (Diptera: Tephritidae), is a significant pest causing sizeable economic burden and fruit damage to crops worldwide, especially in the Mediterranean area. In deciduous orchards, monitoring the population of Mediterranean flies is an intensive and expensive process. This study aimed to explore alternatives to optimise the time and effort-intensive practice of medfly field monitoring, and promote site-specific management strategies, such as targeted pesticide applications or mass trapping, which could be implemented in high-density areas identified within orchards. In our previous work, the medfly population was found to begin infestation in small locations (few trees) within the orchard. This dynamic often precedes the infestations in the rest of the orchard. This study aims to characterise the differences between these locations (termed 'hot spots') and areas representing the rest of the orchard (termed 'cold spots'). We examined differences in microclimate conditions (temperature, humidity and leaf area index) in apple orchards and quantified fruits nutrient level. The results characterised hot spots (HS) with a higher leaf area index, lower temperatures and higher humidity than cold spots. In addition, the fruits in the HS had higher nitrogen levels. To deepen our investigation, we also used remote sensing validation with thermal images to assess its potential for future hotspot detection. The differences we found can help to identify HS in other orchards and provide guidelines for using this knowledge to optimise pest control.

Styrax is the largest genus of the family Styracaceae, with about 130 species distributed across America, Europe, and Southeast Asia. The oleo-resin of these woody shrubs, called Styrax benzoin, has a long tradition of use as incense and in therapeutics, which has stimulated research and industrial applications. Many studies have been carried out on the biological applications of different Styrax species, but some gaps still remain to be filled, particularly regarding the phenology and the biological activity and application in different fields. Hence, this review gathers updated and valuable information on the distribution and phenology of Styrax spp., considering their phytochemicals, biological activity, current and possible applications in medicine, animal feeding, energy production, and the food industry. Overall, Styrax obassia and Styrax japonicus are the most studied, but Styrax officinalis has been thoroughly investigated for its phytochemicals. The recent literature highlights promising applications in oncology and also as an energy crop. The data described in this review could be useful in upgrading the quantity and quality of Styrax benzoin, as well as expanding knowledge on emerging applications, such as bio-pesticides or the development of active packaging for the food industry.

From an agricultural perspective, carrots are a significant tap root vegetable crop in the Apiaceae family because of their nutritional value, health advantages, and economic importance. The edible part of a carrot, known as the storage root, contains various beneficial compounds, such as carotenoids, anthocyanins, dietary fiber, vitamins, and other nutrients. It has a crucial role in human nutrition as a significant vegetable and raw material in the nutraceutical, food, and pharmaceutical industries. The cultivation of carrot fields is susceptible to a wide range of biotic and abiotic hazards, which can significantly damage the plants’ health and decrease yield and quality. Scientific research mostly focuses on important biotic stressors, including pests, such as nematodes and carrot flies, as well as diseases, such as cavity spots, crown or cottony rot, black rot, and leaf blight, caused by bacteria, fungi, and oomycetes. The emerging challenges in the field include gaining a comprehensive understanding of the interaction between hosts and pathogens in the carrot–pathogen system, identifying the elements that contribute to disease development, expanding knowledge of systemic treatments, exploring host resistance mechanisms, developing integrated control programs, and enhancing resistance through breeding approaches. In fact, the primary carrot-growing regions in tropical and subtropical climates are experiencing abiotic pressures, such as drought, salinity, and heat stress, which limit carrot production. This review provides an extensive, up-to-date overview of the literature on biotic and abiotic factors for enhanced and sustainable carrot production, considering the use of different technologies for the shelf-life extension of carrots. Therefore, it addresses the current issues in the carrot production chain, opening new perspectives for the exploration of carrots both as a food commodity and as a source of natural compounds.

Volatile phenylpropenes comprise one of the largest groups of plant phenylalanine-derived volatiles that not only possess ecological roles but also exhibit numerous pharmacological activities. Despite their wide distribution in the plant kingdom, biosynthesis of only a small subset of these compounds has been discovered. Here, we elucidated yet unknown steps in the biosynthesis of isoelemicin and elemicin using carrot (Daucus carota subsp. sativus), which produces a wide spectrum of volatile phenylpropenes, as a model system. Comparative transcriptomic analysis combined with metabolic profiling of two carrot cultivars producing different spectrums and levels of phenylpropene compounds revealed that biosynthesis of isoelemicin and elemicin could proceed via the (iso)eugenol-independent pathway, which diverges from the lignin biosynthetic pathway after sinapyl alcohol. Moreover, in planta results showed that two different NADPH-dependent reductases, a newly identified 5-methoxy isoeugenol synthase (DcMIS) and previously characterized (iso)eugenol synthase (DcE(I)GS1), both of which use sinapyl acetate as a substrate, are responsible for the biosynthesis of immediate precursors of isoelemicin and elemicin, respectively. In contrast to penultimate reactions, the final steps in the formation of these phenylpropenes are catalyzed by the same newly characterized methyltransferase, S-adenosyl-l-methionine:5-methoxy(iso)eugenol O-methyltransferase, that methylates the para-hydroxyl group of their respective precursors, thus completing the (iso)eugenol-independent route for the biosynthesis of isoelemicin and elemicin.

Plant apocarotenoids have been shown to have a diverse biological role in herbivore–plant interactions. Despite their importance, little is known about herbivores' effect on apocarotenoid emissions in Lactuca sativa. In this study, we examined changes in apocarotenoid emissions in lettuce leaves after infestation by two insects, viz., Spodoptera littoralis larvae and Myzus persicae aphids. We found that β-ionone and β-cyclocitral showed higher concentrations than the other apocarotenoids, with a significant increase as per the intensity of infestation of both herbivore species. Furthermore, we performed functional characterization of Lactuca sativa carotenoid cleavage dioxygenase 1 (LsCCD1) genes. Three LsCCD1 genes were overexpressed in E. coli strains, and recombinant proteins were assayed for cleavage activity on an array of carotenoid substrates. The LsCCD1 protein cleaved β-carotene at the 9,10 (9′,10′) positions producing β-ionone. The transcript analysis of LsCCD1 genes revealed differential expression patterns under varying levels of herbivores' infestation, but the results were inconsistent with the pattern of β-ionone concentrations. Our results suggest that LsCCD1 is involved in the production of β-ionone, but other regulatory factors might be involved in its induction in response to herbivory. These results provide new insights into apocarotenoid production in response to insect herbivory in lettuce.

Horticultural crops are an essential part of food and nutritional security. Moreover, these form an integral part of the agricultural economy and have enormous economic potential. They are a rich source of nutrients that are beneficial to human health. Plant breeding of horticultural crops has focussed primarily on increasing the productivity and related traits of these crops. However, fruit and vegetable quality is paramount to their perishability, marketability, and consumer acceptance. The improved nutritional value is beneficial to underprivileged and undernourished communities. Due to a declining genetic base, conventional plant breeding does not contribute much to quality improvement as the existing natural allelic variations and crossing barriers between cultivated and wild species limit it. Over the past two decades, ‘omics’ and modern biotechnological approaches have made it possible to decode the complex genomes of crop plants, assign functions to the otherwise many unknown genes, and develop genome-wide DNA markers. Genetic engineering has enabled the validation of these genes and the introduction of crucial agronomic traits influencing various quality parameters directly or indirectly. This review discusses the significant advances in the quality improvement of horticultural crops, including shelf life, aroma, browning, nutritional value, colour, and many other related traits.

Stem rot, caused by the Sclerotium rolfsii, imposes severe yield losses in peanuts (Arachis hypogaea L.) worldwide. Breeding for resistance is challenging because not enough is known about mechanisms for resistance. The goals of this study were to (a) evaluate the field resistance of recombinant inbred lines derived from a resistant x susceptible cross, (b) associate quantitative loci (QTLs), and (c) reveal potential mechanisms for resistance. Lines were inspected during 3 yr in field conditions. Plants were manually inoculated and rated for three parameters: disease level, number of damaged plants/center, and disease power. Significant effects were found for the lines and the environment in all three parameters. Heritability and year-to-year correlations were highly significant, suggesting a consistent response of the lines to the stem rot pressure. Quantitative trait loci mapping was performed based on a previously constructed genetic map. Overall, 20 significant QTLs were found for the resistance parameters, concentrating in four locations on chromosomes A07, A03, B03, and B05. Out of the four loci, three were reported in previous studies with different genetic backgrounds suggesting a wide effect. The B05 QTL was the strongest, with the phenotypic variation explained of 11.6-21.7%. Interestingly, this QTL is colocalized with a previously identified major locus for branching habit trait. An additional field trial performed on 14 lines found a significant branching habit effect, wherein bunch-types lines were more resistant than spreading-types, suggesting that plant architecture can be a possible factor influencing the infection rate of S. rolfsii on the field level.

Laurus nobilis L. is an aromatic medicinal plant widely cultivated in many world regions. L. nobilis has been increasingly acknowledged over the years as it provides an essential contribution to the food and pharmaceutical industries and cultural integrity. The commercial value of this species derives from its essential oil, whose application might be extended to various industries. The chemical composition of the essential oil depends on environmental conditions, location, and season during which the plants are collected, drying methods, extraction, and analytical conditions. The characterization and chemotyping of L. nobilis essential oil are extremely important because the changes in composition can affect biological activities. Several aspects of the plant's secondary metabolism, particularly volatile production in L. nobilis, are still unknown. However, understanding the molecular basis of flavor and aroma production is not an easy task to accomplish. Nevertheless, the time-limited efforts for conservation and the unavailability of knowledge about genetic diversity are probably the major reasons for the lack of breeding programs in L. nobilis. The present review gathers the scientific evidence on the research carried out on Laurus nobilis L., considering its cultivation, volatile composition, biochemical and molecular aspects, and antioxidant and antimicrobial activities.

Acorus calamus is a perennial aromatic medicinal plant from the Acorusaceae family, known for its pharmaceutical and medicinal value. A combined chemical, biochemical, and molecular study was conducted to evaluate the differential accumulation of volatile organic compounds (VOCs) in rhizomes and leaves of A. calamus essential oil. Here, we performed VOC profiling and transcriptome-based identification and functional characterization of terpene synthase (TPS) genes. A total of 110 VOCs were detected from the rhizomes and leaves of A. calamus, and some VOCs showed significant differences between them. The further transcriptome-based analysis led to the identification of six putative TPSs genes. In phylogenetic analysis, three TPSs belonged to the TPS-g clade, one to each of the TPS-a, TPS-c, and TPS-e clades. The heterologous E. coli-based expression of recombinant TPSs identified three genes (AcTPS3, AcTPS4, and AcTPS5) as bifunctional linalool/nerolidol synthase. The correlation of TPS gene expression and VOC metabolite profiles supported the function of these genes in A. calamus. Our findings provide a roadmap for future efforts to enhance the molecular mechanisms of terpene biosynthesis and our understanding of Acorus-insect interactions.

Hyoscyamine, anisodamine and scopolamine are tropane alkaloids present in some Solanaceae species and used in modern medicine. L-Hyoscyamine is hydroxylated to 6β-hydroxyhyoscyamine (anisodamine) and then epoxidated to scopolamine by the dual action of hyoscyamine 6β-hydroxylase (H6H), a 2-oxoglutarate dependent dioxygenase. A natural mutation in the Gly-220 residue to Cys was previously shown to be associated with the loss of function of H6H in Mandragora officinarum, preventing the accumulation of anisodamine and scopolamine in these plants. We show here that a deliberate Gly220Cys mutation in the Datura innoxia DiH6H protein caused a loss of both its enzymatic abilities and rendered it unable to hydroxylate L-hyoscyamine into anisodamine and to epoxidate anisodamine into scopolamine. By using protein modeling based on an available crystal structure of H6H from Datura metel, we show how the Cys220 residue causes a steric interference in the active site cavity impairing the interaction of both substrates, hyoscyamine and anisodamine with the active site of the protein. We also address the enantiomeric preference of DiH6H based on molecular modeling.

Under reduced solar UV radiation, such as in polycarbonate-covered nurseries, the two-spotted spider mite Tetranychus urticae is a major pest of all citrus cultivars, while under natural solar radiation, only sensitive cultivars are infested. We hypothesized that citrus resistance to T. urticae is induced by UV. We infested seedlings of Citrus volkameriana rootstock with T. urticae under natural and under UV-screened solar radiation, along with non-infested control seedlings. We then monitored the establishment of the spider mites and analyzed the volatile leaf profile using GC-MS. The density of spider mites was reduced dramatically on seedlings exposed to solar UV. Overall, ninety volatile compounds (47 monoterpenes, 35 sesquiterpenes, and 8 aldehydes) were detected in the leaves, many of them known to be herbivore-induced and/or UV enhanced. Their levels were affected not only by solar UV radiation or by mite infestation independently. Synergistic interaction of these two factors resulted in 90% of the volatiles suppressed by T. urticae infestation in the absence of UV radiation. This suggests that plant induced resistance is dependent on exposure to UV radiation.

Carrot psylla is one of the devastating pests of carrot throughout northern Europe and the Mediterranean basin. Here we characterized the behavioral response of psylla females towards different carrot germplasm and identified the chemical cues involved in the host selection of psylla females by oviposition choice experiments and metabolic profiling of leaf volatiles. In choice assays, carrot psylla displayed differential responses to tested 14 germplasm. Among germplasm, wild accessions 21793 and 20465 were highly preferred by carrot psylla, while wild accessions 20465 and the orange cultivar Nairobi were less. In non-choice experiments conducted only with this four-germplasm revealed that the carrot psylla females gave higher preference to the Nairobi and wild accession 20465, indicating the vicinity to other host plants in the same area might affect female preference. Moreover, the nymph development and survival experiments showed the lowest nymphs survival rate on the wild accessions 21793 and 20497. Furthermore, the volatile emissions among different carrot cultivars infested with psylla showed qualitative and quantitative differences versus intact plants. Among these volatiles, apiol, β-asarone, myristicin, and sabinene showed a relationship with psyllas growth and survival. We also showed that myristicin and sabinene exogenous applications caused a dramatic reduction in the number of eggs laid by psylla and subsequent nymph survival. This is an initial study of the volatiles that mediate attraction and oviposition preference of carrot psylla in response to its host plant. The results from this study provide baseline information for the development of new control strategies against carrot psylla.

β-Ionone is a natural plant volatile compound, and it is the 9,10 and 9′,10′ cleavage product of β-carotene by the carotenoid cleavage dioxygenase. β-Ionone is widely distributed in flowers, fruits, and vegetables. β-Ionone and other apocarotenoids comprise flavors, aromas, pigments, growth regulators, and defense compounds; serve as ecological cues; have roles as insect attractants or repellants, and have antibacterial and fungicidal properties. In recent years, β-ionone has also received increased attention from the biomedical community for its potential as an anticancer treatment and for other human health benefits. However, β-ionone is typically produced at relatively low levels in plants. Thus, expressing plant biosynthetic pathway genes in microbial hosts and engineering the metabolic pathway/host to increase metabolite production is an appealing alternative. In the present review, we discuss β-ionone occurrence, the biological activities of β-ionone, emphasizing insect attractant/repellant activities, and the current strategies and achievements used to reconstruct enzyme pathways in microorganisms in an effort to to attain higher amounts of the desired β-ionone.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Carotenogenesis has been intensively studied in carrot roots, and transcriptional regulation is thought to be the major factor in carotenoid accumulation in these organs. However, little is known about the transcriptional regulation of carotenoid biosynthetic genes concerning carotenoid accumulation during infestation by the obligate parasite Phelipanche aegyptiaca . HPLC analysis revealed a decrease in carotenoid levels of the different carrot cultivars when parasitized by P . aegyptiaca . Besides, we isolated and analyzed P . aegyptiaca tubercles parasitizing the various carrot root cultivars and show that they accumulate different carotenoids compared to those in non-infested carrot roots. Expression analysis of PHYTOENE SYNTHASE ( PSY1) and CAROTENOID ISOMERASE ( CRTISO ) as well as the strigolactone apocarotenoid biosynthetic genes DWARF27 ( D27 ), CAROTENOID CLEAVAGE DIOXYGENASE 7 ( CCD7 ) and CCD8 revealed that their transcript levels showed significant variation in P . aegyptiaca infested carrot roots. After parasite infestation, the expression of these genes was strongly reduced, as were the carotenoid levels and this was more pronounced in the uncommon non-orange varieties. We also analyzed the parasite genes encoding D27, CCD7 and CCD8 and show that they are expressed in tubercles. This raises important questions of whether the parasite produces its carotenoids and apocarotenoids including strigolactones and whether the latter might have a role in tubercle development.

The black fig fly (Silba adipata) is one of the major pests of figs worldwide. This study investigated the effect of pollination on black fig fly infestation and volatile emission during fruit development of facultative parthenocarpic Ficus carica. The results from in-field oviposition preference of black fig fly, olfactory analysis, and fruit volatile profiles indicate that the black fig fly gave a strong preference to unpollinated figs that showed higher emissions of volatile organic compounds. Terpenes are known to be important compounds determining many insect-plant interactions, so we report a transcriptome-based identification and functional characterization of a terpene synthase (TPS) gene family in F. carica. The protein expression in Escherichia coli of eight terpene synthases (TPSs) revealed that three were monoterpene synthases belonging to the TPS-b clade, with FcTPS6 catalyzing the formation of 1,8-cineole while the other two converted GPP into linalool. Four sesquiterpene synthases from the TPS-a clade catalyze the formation of germacrene D (FcTPS1), E-β-caryophyllene (FcTPS2), cadinene (FcTPS3) and δ-elemene (FcTPS5) while one sesquiterpene synthase FcTPS4 from the TPS-b clade showed nerolidol synthase activity. Most of the enzymatic products closely matched the volatile terpenes emitted from fig fruits and all the genes were expressed during fruit development. This study provides new insights into fig-insect interactions and understanding the molecular mechanisms of terpene biosynthesis and could provide the foundations for sustainable pest management strategies.