Volatiles from host plant brinjal attract the brinjal Fruit and Shoot Borer -Leucinodes orbonalis Guenee

Brinjal Fruit and Shoot Borer- Leucinodes orbonalis Guenee is a major insect pest on brinjal- Solanum melongena worldwide. An effective strategy used in developing pest controlling agents is the synergism between insect pheromones and host plant volatiles, which can increase the attraction of insect pest. The present study was aimed at investigating the chemical constituents and attractant effects of the volatiles extracted from different parts of the host plant brinjal on the behavior of adult L. orbonalis. Bioassay using Y-shaped olfactometer revealed that the one-day old virgin female, gravid female and male insects respond positively to the host plant volatiles extracted from fruits, leaves and shoots but not to that of flowers. It was shown that the gravid females were significantly attracted to all three volatiles (p < 0.05). Bioassay using X-shaped olfactometer identified that all three types of insects highly preferred the volatiles from fruits (p < 0.05). Gas chromatography-mass spectrometry analysis of volatiles indicated that brinjal plant produces volatile secondary metabolites, which include 2,2′-(Ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl) dibenzoate (12.11%), 3,7-dimethylocta-1,6-dien-3-ol (22.38%), Benzyl alcohol (22.9%) and Benzyl alcohol (27.06%) as major constituents from fruits, shoots, leaves and flowers respectively. Responses of insects to the volatiles from host plant in the absence of visual cues direct us to focus on the importance of host plant volatiles to locate the plant. Results of this study emphasize the major role that host plant volatiles play in the attraction of insect pests towards the plant.     

Do diet and taxonomy influence insect gut bacterial communities?

Many insects contain diverse gut microbial communities. While several studies have focused on a single or small group of species, comparative studies of phylogenetically diverse hosts can illuminate general patterns of host–microbiota associations. In this study, we tested the hypotheses that (i) host diet and (ii) host taxonomy structure intestinal bacterial community composition among insects. We used published 16S rRNA gene sequence data for 58 insect species in addition to four beetle species sampled from the Sevilleta National Wildlife Refuge to test these hypotheses. Overall, gut bacterial species richness in these insects was low. Decaying wood xylophagous insects harboured the richest bacterial gut flora (102.8 species level operational taxonomic units (OTUs)/sample ± 71.7, 11.8 ± 5.9 phylogenetic diversity (PD)/sample), while bees and wasps harboured the least rich bacterial communities (11.0 species level OTUs/sample ± 5.4, 2.6 ± 0.8 PD/sample). We found evidence to support our hypotheses that host diet and taxonomy structure insect gut bacterial communities (P < 0.001 for both). However, while host taxonomy was important in hymenopteran and termite gut community structure, diet was an important community structuring factor particularly for insect hosts that ingest lignocellulose‐derived substances. Our analysis provides a baseline comparison of insect gut bacterial communities from which to test further hypotheses concerning proximate and ultimate causes of these associations.     

Electrophysiological and behavioral responses of Asian and European honeybees to pear flower volatiles

Honeybee pollination behavior is influenced by flower volatiles, which honeybees sense via olfactory receptors. Honeybees are only weakly attracted to pear flowers. To investigate the potential reasons, we extracted and determined the floral volatile compounds from three pear cultivars (Su, Ya, and Xuehua) using headspace solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC–MS). The effects of pear flower volatiles on the Asian honeybee (Apis cerana cerana Fabricius) and the European honeybee (Apis mellifera ligustica Spinola) were determined by electroantennogram (EAG) assays and behavioral tests in a three-arm olfactometer. Among the 76 flower volatiles detected with GC–MS, 21 were found in all three pear cultivars, accounting for approximately 70% of the total volatile content. 3-Methyl-1-butanol and (+)-limonene volatiles had the highest relative content. Five compounds elicited strong EAG responses in both bee species: 2-methylbutyraldehyde, 1-nonanal, 6-methyl-5-hepten-2-one, 3-methyl-1-butanol, and (+)-limonene. Neither bee species showed positive taxis to these volatiles. In behavioral tests, A. mellifera ligustica showed a low preference for 6-methyl-5-hepten-2-one (20%, 400 µg/µL) and 2-phenethyl alcohol (16.7%, 400 µg/µL). Apis cerana cerana showed a low preference for 6-methyl-5-hepten-2-one (6.7%, 400 µg/µL) and 1-nonanal (10%, 400 µg/µL), whereas its preferences for 3-methyl-1-butanol (43.3%, 400 µg/µL) and α-farnesene (40%, 400 µg/µL) were similar to that for the control. Therefore, a lack of attractive volatile compounds could explain why honeybees are only weakly attracted to pear flowers. Therefore, to achieve acceptable pollination in pear orchards, we suggest using flower-scent sugar syrup feeding and a saturation pollination strategy.     

Influence of feed on anti-inflammatory and antioxidant effects of Zophobas morio

In this study, the antioxidant and anti-inflammatory effects of superworm as one of the potential species for the food industry were investigated. This type of insect was bred on three different types of feed and, at the end of the breeding experiment, the total polyphenols (TPC), antiradical activity, degree of hydrolysis, and anti-inflammatory effects of the peptides were determined. The highest value of polyphenols content was demonstrated in whole enzymatically hydrolysed insects (W), especially in the group fed on soy feed (Wso = 4.2014 ± 0.27 mg GAE/100 g). This group also achieved the highest antiradical activity, as measured by ABTS and DPPH, and the highest anti-inflammatory effect, as measured by COX inhibition. Insects fed on soy feed are unsuitable for food despite their high polyphenol content and antioxidant activity, as high mortality occurs. The largest length in a worm breeding experiment was identified in the group fed the control diet (co = 4.93 ± 0.27 cm) and the heaviest weight in the group on the maize diet (ma = 0.77 ± 0.11 g).     

The importance of relative humidity and trophic resources in governing ecological niche of the invasive carabid beetle Merizodus soledadinus in the Kerguelen archipelago

Comprehensive studies to identify species-specific drivers of survival to environmental stress, reproduction, growth, and recruitment are vital to gaining a better understanding of the main ecological factors shaping species habitat distribution and dispersal routes. The present study performed a field-based assessment of habitat distribution in the invasive carabid beetle Merizodus soledadinus for the Kerguelen archipelago. The results emphasised humid habitats as a key element of the insect’s realised niche. In addition, insects faced food and water stress during dispersal events. We evaluated quantitatively how water availability and trophic resources governed the spatial distribution of this invasive predatory insect at Îles Kerguelen. Food and water stress survival durations [in 100%, 70%, and 30% relative humidity (RH) conditions] and changes in a set of primary metabolic compounds (metabolomics) were determined. Adult M. soledadinus supplied with water ad libitum were highly tolerant to prolonged starvation (LT₅₀ = 51.7 ± 6.2 d). However, food-deprived insect survival decreased rapidly in moderate (70% RH, LT₅₀ = 30.37 ± 1.39 h) and low (30% RH, LT₅₀ = 13.03 ± 0.48 h) RH conditions. Consistently, body water content decreased rapidly in insects exposed to 70% and 30% RH. Metabolic variation evidenced the effects of food deprivation in control insects (exposed to 100% RH), which exhibited a progressive decline of most glycolytic sugars and tricarboxylic acid cycle intermediates. Most metabolite levels were elevated levels during the first few hours of exposure to 30% and 70% RH. Augmented alanine and lactate levels suggested a shift to anaerobic metabolism. Simultaneously, peaks in threonine and glycolytic sugars pointed to metabolic disruption and a progressive physiological breakdown in dehydrating individuals. Overall, the results of our study indicate that the geographic distribution of M. soledadinus populations is highly dependent on habitat RH and water accessibility.     

Floral sesquiterpenes and their synthesis in dioecious kiwifruit

Kiwifruit species are vigorously growing dioecious vines that rely on bees and other insects for pollen transfer between spatially separated male and female individuals. Floral volatile terpene cues for insect pollinator attraction were characterized from flowers of the most widely grown and economically important kiwifruit cultivar Actinidia deliciosa ‘Hayward’ and its male pollinator ‘Chieftain’. The sesquiterpenes α-farnesene and germacrene D dominated in all floral tissues and the emission of these compounds was detected throughout the day, with lower levels at night. Two terpene synthase (TPS) genes were isolated from A. deliciosa petals that produced (+)-germacrene D and (E,E)-α-farnesene respectively. Both TPS genes were expressed in the same tissues and at the same times as their corresponding floral volatiles. Here we discuss these results with respect to plant and insect ecology and the evolution and structure of sesquiterpene synthases.Key words: terpene, dioecy, kiwifruit, volatile, ecology, evolution, flower     

Identification of olfactory receptor neurons in Uraba lugens (Lepidoptera: Nolidae) and its implications for host range

Phytophagous insects detect volatile compounds produced by host and non-host plants, using species-specific sets of olfactory receptor neurons (ORNs). To investigate the relationship between the range of host plants and the profile of ORNs, single sensillum recordings were carried out to identify ORNs and corresponding active compounds in female Uraba lugens (Lepidoptera: Nolidae), an oligophagous eucalypt feeder. Based on the response profiles to 39 plant volatile compounds, 13 classes of sensilla containing 40 classes of ORNs were identified in female U. lugens. More than 95% (163 out of 171) of these sensilla contained 16 classes of ORNs with narrow response spectra, and 62.6% (107 out of 171) 18 classes of ORNs with broad response spectra. Among the specialized ORNs, seven classes of ORNs exhibited high specificity to 1,8-cineole, (±)-citronellal, myrcene, (±)-linalool and (E)-β-caryophyllene, major volatiles produced by eucalypts, while nine other classes of ORNs showed highly specialized responses to green leaf volatiles, germacrene D, (E)-β-farnesene and geranyl acetate that are not produced by most eucalypts. We hypothesize that female U. lugens can recognize their host plants by detecting key host volatile compounds, using a set of ORNs tuned to host volatiles, and discriminate them from non-host plants using another set of ORNs specialized for non-host volatiles. The ORNs with broad response spectra may enhance the discrimination between host and non-host plants by adding moderately selective sensitivity. Based on our finding, it is suggested that phytophagous insects use the combinational input from both host-specific and non-host specific ORNs for locating their host plants, and the electrophysiological characterization of ORN profiles would be useful in predicting the range of host plants in phytophagous insects.     

Volatile compounds secreted by Brindley's glands of adult Triatoma infestans: identification and biological activity of previously unidentified compounds.

Volatile emissions of adult male Triatoma infestans were collected on non-polar SPME fibers and analyzed by gas chromatography linked to a mass spectrometer. A complex mixture of 16 short-chain esters and acids were identified. The composition of short-chain aliphatic acids (ethanoic to nonanoic acids) was similar to previously reported results. The most abundant aliphatic acid was 2-methylpropanoic acid, constituting 18% of the total volatile content. Also abundant were the esters 2- and 3-methylbutyl 2-methylpropanoate, which constituted 30% and 22%, respectively, of the total volatile content. A similar pattern of compounds was observed in the volatiles secreted by dissected male Brindley's glands; however, in this case, 2- and 3-methylbutan-1-ol were detected which were not found in live insect volatile emissions. Large variability in volatile composition was also observed among the glands excised from different insects. Electroantennographic (EAG) evaluation of the components of Brindley's gland showed significant responses for 2- and 3-methylbutyl 2-methylpropanoate compared to controls. The mixture of volatiles secreted by excised Brindley's glands and the isolated 2- and 3-methylbutyl 2-methylpropanoate had repellent effects on both male and female T. infestans, possibly associated with a defensive strategy.     

Comparison of volatile leaf compounds and herbivorous insect communities on three willow species

 Plants produce volatile compounds known to influence insect preferences for oviposition and feeding. To examine whether volatile leaf compounds are correlated with the herbivorous insect community, we analyzed volatile compounds in leaves from three co-occurring willow species, Salix serissaefolia, S. eriocarpa, and S. integra, and investigated their associated insect communities in 3 months across different years. The gas chromatographic profiles of volatile compounds were highly specific to each willow species and remained constant in the study months. In a comparison between the chemical composition of the volatile compounds and the taxon composition of the insect communities, dissimilarity patterns in chemical composition among the three willow species were very close to those in herbivorous insect communities. These findings indicate that willow leaves produce specific volatiles that are highly correlated with the community structure of herbivorous insects associated with them. Received: October 10, 2002 / Accepted: March 17, 2003     

Volatiles from Botrytis cinerea‐infected and healthy berries of Vitis vinifera influence the oviposition behaviour of Epiphyas postvittana

Interactions among plants, plant‐feeding insects, and plant – pathogenic fungi are partially mediated by volatile compounds. Herbivorous insects use sensory cues to choose host plants for feeding and/or oviposition that are likely to support survival and development of progeny. It is known that some fungus‐induced alterations in plants can modify plant volatiles, which are recognized by the olfactory receptors of the insect, either as an attractant or as a deterrent. We tested for the presence of behaviour‐modifying volatiles emanating from the berries of Vitis vinifera L. (Vitaceae) infected with Botrytis cinerea Pers. (Helotiales). We tested the olfactory behaviour of adults of Epiphyas postvittana Walker (Lepidoptera: Tortricidae) to these volatiles using two‐choice and wind‐tunnel experiments. We hypothesized that olfactory cues influence E. postvittana's oviposition behaviour. We found that volatiles emanating from B. cinerea‐infected berries did not significantly attract the gravid females of E. postvittana; consequently, they laid significantly fewer eggs on infected berries. Furthermore, significantly fewer females of E. postvittana were found attracted to infected berries in the wind tunnel assay. Ethanol and 3‐methyl‐1‐butanol were abundant in B. cinerea‐infected berries. Oviposition assays made with laboratory standards of ethanol and 3‐methyl‐1‐butanol confirmed their role in regulating the olfactory behaviour of E. postvittana site selection.     

Volatiles that encode host-plant quality in the grapevine moth

Plant volatiles are signals used by herbivorous insects to locate host plants and select oviposition sites. Whether such volatiles are used as indicators of plant quality by adult insects in search of host plants has been rarely tested. We tested whether volatiles indicate plant quality by studying the oviposition of the grapevine moth Lobesia botrana on the grapevine plant Vitis vinifera. Host plants were infected with a variety of microorganisms, and larval fitness was correlated to the infected state of the substrate. Our results show an oviposition preference for volatiles that is significantly correlated with the fitness of the substrate. The chemical profiles of the bouquets from each V. vinifera–microorganism system are clearly differentiated in a PCA analysis. Both the volatile signal and the quality of the plant as larval food were affected by the introduction of microorganisms. Our study represents a broad approach to the study of plant–insect interactions by considering not only the direct effect of the plant but also the effect of plant–microorganism interactions on insect population dynamics.     

A study of chemical Composition,Antioxidants, and volatile compounds in roasted Arabic coffee

Coffea arabica (Rubiaceae) is a basic drink for all Gulf societies, especially Saudi Arabia, it is the main part of the Saudi tradition. This investigation was carried out to track the chemical composition, caffeine content by UV–visible spectrophotometer, acrylamide content by using a gas chromatograph, free radical scavenging capacity by DPPH methods as well as determined the browning index and separated the volatiles compounds using GC–MS for the most common three degree of roasted Arabic coffee; light (180 ± 10 °C; 6.0 ± 1.0 min), medium (180 ± 10 °C; 8.0 ± 1.0 min), and dark (180 ± 10 °C; 10.0 ± 1.0 min). Data revealed that light roasted coffee has the highest significant (p < 0.05) value of moisture content (4.80%), crude protein (13.05%), and lowest value of ether extract (10.39%) and crude fiber (24.24%). The caffeine content was found to be 1.13% in light coffee, which increased to 1.17% in medium coffee, then decreased to 1.08% in dark coffee. The quantity of acrylamide detected in light roasted coffee (0.41 mg/100 g) was the greatest, whereas medium roasted coffee comparatively produced low amounts (0.31 mg/100 g). The light roasted coffee gave the highest antioxidant activity (88.72 mg TE/g), while the dark roasted coffee gave the least activity (78.76 mg TE/g). Browning index increases with roasting time. Hydrocarbons, alcohols, and esters were the most represented in roasted coffee headspace. Silanes and sec-butyl nitrite compounds were absent in the medium roasted headspace. Except for amines, all 11 classes of volatile compounds were present in the headspace of dark roasted coffee.     

Effects of native pollinator communities on the physiological and chemical parameters of loquat tree (Eriobotrya japonica) under open field condition

Wild and managed pollinators are the key component of biodiversity, contributing to important ecosystem services such as pollination and supporting human food security. Pollination by insects is a crucial component of the food chain that ensures the production of fruits and strongly affects the fruit quality, but the effect of insect pollination on fruit physiological and chemical parameters is largely unknown. The current study was conducted to determine the insect pollinators diversity and their relative abundance in the loquat (Eriobotrya japonica) orchard during 2017–2019. Further, the effect of insect pollinators pollination on the physiological and chemical parameters of fruit quality as compared to control pollinated flowers was investigated. The results revealed that a total of 22 species from 3 families (Apidae, Halictidae, and Syrphidae) were identified during the flowering season. The Apidae and Syrphidae were the most frequently observed families with major groups honey bees (67.89%) and hoverflies (21.57%), respectively. Moreover, results indicated that the fruit yield by the open-pollinated flowers (22.31 ± 0.34 kg/tree) was significantly higher than the control pollinated flowers (14.80 ± 0.25 kg/tree). Physiological and chemical parameters of loquat fruit differed significantly when fruits obtained from open-pollinated flowers as compared to control pollinated flowers. These results suggested that native insect pollinators play important role in the fruit quality of loquat. Hence, maintenance of appropriate habitat of native pollinators near loquat orchards is necessary to ensure good productivity and fruit quality.     

Volatile compounds of endophyte-free and infected tall fescue (Festuca arundinacea Schreb.).

Volatile compounds produced by intact plants and ground leaf tissue from endophyte-infected (E+) and endophyte-free (E-) tall fescue (Festuca arundinacea Schreb.) were collected by a purge-and-trap procedure and analyzed by gas chromatography/mass spectrometry The volatile compound profile from ground leaf tissue was similar between E+ and E- clonal plants; however, the sheaths of E+ clonal plants produced higher levels of 1-octen-3-ol, a characteristic volatile compound derived from lipid peroxidation in fungi, which was absent in E- clonal plants. Intact plants produced fewer volatiles than macerated leaves. At 25 degrees C, (Z)-3-hexen-1-ol acetate was the most abundant compound, accounting for 77 and 89% of the total volatile emission from E+ and E- plants, respectively. Higher temperature (32 degrees C) significantly reduced the production of (Z)-3-hexen-1-ol acetate. Nonanal was the most abundant compound at 32 degrees C accounting for 52 and 45% of the total volatile emission from E+ and E- plants. Treatment of E+ and E- plants with jasmonic acid (JA) dramatically altered the volatile compound profile. The levels of (E)-beta-ocimene increased more than 200-fold and accounted for at least 43% of the total volatile emission. Although the presence of endophyte resulted in some qualitative and quantitative differences in the production of volatile compounds, they are unlikely to account for the differences in insect resistance between E+ and E- plants. Nevertheless, the production of a unique spectrum of volatiles after JA treatment may represent a significant plant-based defense response in tall fescue that is independent of endophyte.     

Synthesis of some novel pyridine compounds containing bis‐1,2,4‐triazole/thiosemicarbazide moiety and investigation of their antioxidant properties,carbonic anhydrase,and acetylcholinesterase enzymes inhibition profiles

Some novel derivatives of thiosemicarbazide and 1,2,4‐triazole‐3‐thiol were synthesized and evaluated for their biological activities. The title compounds were prepared starting from readily available pyridine‐2,5‐dicarboxylic acid. The reaction carboxylic acid with absolute ethanol afforded the corresponding dimethyl pyridine‐2,5‐dicarboxylate ( 1 ). The reaction of dimethyl‐2,5‐pyridinedicarboxylate ( 1 ) with hydrazine hydrate good yielded pyridine‐2,5‐dicarbohydrazide ( 2 ). Refluxing compound 2 with alkyl/aryl isothiocyanate derivatives for 3–8 h afforded 1,4‐disubstituted thiosemicarbazides ( 3a–e ). Base‐catalyzed intra‐molecular dehydrative cyclization of these intermediates furnished the 4,5‐disubstituted bis‐mercaptotriazoles ( 4a–e ) in good yield (85%–95%). Among the target compounds, 2,2′‐(pyridine‐2,5‐diyldicarbonyl)bis[N‐(p‐methoxyphenyl)hydrazinecarbothioamide] ( 3c ) showed very high activity with value of 72.93% against 1,1‐diphenyl‐2‐picrylhydrazyl free radical at the concentration of 25 μg/mL. The inhibitory effects of the target compounds against acetylcholinesterase (AChE), hCA I, and II were studied. AChE, cytosolic hCA I and II isoforms were potently inhibited by synthesized these derivatives with K_is in the range of 3.07 ± 0.76–87.26 ± 29.25 nM against AChE, in the range of 1.47 ± 0.37–10.06 ± 2.96 nM against hCA I, and in the range of 3.55 ± 0.57–7.66 ± 2.06 nM against hCA II, respectively.     

储粮环境挥发性化合物与储粮害虫的关系研究进展

每种粮食的储粮环境中都存在有其特征性挥发物,储粮害虫的发生对储粮环境中挥发物具有重要影响。本文简述了顶空式固相微萃取法、浸入式固相微萃取法、电子鼻检测法等储粮挥发物的提取方法及其优缺点,对小麦 Triticum aestivum L.、稻谷 Olyza sativa L.、玉米 Zea mays L.和燕麦 Avena sativa L.等主要储藏粮食种类的挥发性化合物成分、粮食挥发物对昆虫行为反应的影响、主要储粮害虫(赤拟谷盗 Tribolium castaneum、锈赤扁谷盗 Cryptolestes ferrugineus 和象虫 Sitophilus spp.)发生与粮食挥发物的关系等研究进展进行综述,探讨了储粮环境挥发性化合物与储粮害虫关系未来的研究方向,以期对今后储粮害虫生态防治研究与应用提供参考信息。     

Microflora species and their volatile compounds affecting development of an alcohol dehydrogenase homozygous strain (Adh-I) of Bactrocera (Dacus) oleae (Diptera: Tephritidae)

Microflora species and volatiles emitted from artificial diets were examined from the larvae of three homozygous alcohol dehydrogenase (Adh) strains of the olive fruit fly, Bactrocera (Dacus) oleae (Gmelin), reared under identical conditions. Differences in volatile composition were detected when Adh-I homozygous larvae developed in a diet lacking the preservative p-hydroxybenzoic acid methyl ester (nipagin). Larval development of the Adh-I strain in the preservative-free diet was reduced by 50%, whereas pupal emergence was completely inhibited. The larval development and pupal emergence of Adh-F and Adh-S strains were not affected. Unique microorganisms with characteristic volatile profiles were isolated from the preservative-free diet of the Adh-I strain that were different from those, isolated from Adh-S, Adh-F, laboratory colony, and wild insect populations. Our results indicated that the variations in volatile composition of the artificial diets, and the inhibition of larval development and pupal emergence in Adh-I strain were related to changes in the microflora that developed in the diets of the Adh-I strain.     

Biogeneration of volatile organic compounds produced by <Emphasis Type="Italic">Phormidium autumnale</Emphasis> in heterotrophic bioreactor

The objective of this study was to investigate the volatile organic compounds (VOCs) produced from heterotrophic cultivation of the cyanobacterium Phormidium autumnale with different sources of monosaccharides. The volatiles were isolated by headspace solid-phase micro-extraction in different residence times, separated by gas chromatography, and identified by mass spectrometry (SPME-GC/MS). The profile of volatiles contained a total of 44 volatile compounds when P. autumnale was grown heterotrophically on glucose and 35 when grown on fructose. A combined total of 68 compounds was identified and 11 volatiles were common to both extracts. The compound 3-methyl-butanol was identified among the major volatile compounds formed, reaching a concentration of 141.5 μg mg^?1 dry weight for the glucose-grown cultures and 69.5 μg mg^?1 for the fructose-grown cultures after 144 h. Many of the compounds detected during heterotrophic cultivation originated from terpenoids (β-ionone, β-cyclocitral, and 5,6-epoxy-β-ionone), fatty acids (hexanol, hexanal), or the 2-keto acid pathway (3-methyl-butanol, propanol, butanol).     

Influence of plant growth regulators on volatiles produced by in vitro grown shoots of Agastache rugosa (Fischer & C.A.Meyer) O. Kuntze

The composition of volatile organic compounds emitted by in vitro shoots of Agastache rugosa (Fischer & C.A. Meyer) O. Kuntze (Lamiaceae) was studied using headspace solid-phase microextraction–gas chromatography–mass spectrometry and compared to the those emitted by adult plants and in vitro-germinated seedlings. Shoot-tip explants were cultured on a solid MS medium supplemented with either 4.4 μM 6-benzyladenine (BA), 9.3 μM kinetin, or 0.45 μM thidiazuron and with either 0.57 μM indole-3-acetic acid (IAA) or 0.41 μM picloram. Shoot proliferation was observed in all these treatments. The presence of these plant growth regulators in the culture medium significantly influenced the composition of volatiles as well as morphogenetic responses observed. The number and quality of regenerating shoots and frequency of axillary bud break were highest in medium containing the BA + IAA combination. Sixty-five compounds were identified in the headspace of the in vitro-produced material and plants cultivated in the field. The in vitro shoots emitted both hydrocarbon (limonene, α-pinene) and oxidized (menthone, isomenthone, pulegone) monoterpenes. The composition of monoterpenes differed depending on the type of auxin—rather than cytokinin—in the medium. The emission of phenylallyl compounds, such as estragole, a major compound in field-grown plants, was markedly lower in shoot cultures.     

Development of an efficient micropropagation system for Tecoma stans (L.) Juss. ex Kunth using thidiazuron and effects on phytochemical constitution

The present study was designed to investigate the stimulatory effects of different doses (0.1 to 2.5 μM) of thidiazuron (TDZ) on in vitro shoot induction and proliferation of mature nodal explants of Tecoma stans. Of the tested concentrations, 2.0 μM TDZ proved to be optimal for maximum regeneration (91%) with a mean shoot number of 5.6 ± 0.67, and length of 2.38 ± 0.08 cm, after 4 wk of incubation. To determine the negative effects of prolonged TDZ exposure, after 4 wk of incubation at optimized level of TDZ, the cultures were transferred to a secondary medium either lacking plant growth regulators or supplemented with benzyladenine (BA) alone, or in combination with different auxins (indole-3-acetic acid, indole-3-butyric acid, or α-naphthalene acetic acid; NAA). Among the tested concentrations, 2.5 μM BA in combination with 0.5 μM NAA yielded the maximum mean shoot number (16.60 ± 0.40), and average shoot length (4.76 ± 0.15 cm) after 4 wk of culture. The best rhizogenesis (93%) was achieved on ½ MS medium containing 1.5 μM NAA, with a mean root number of 7.60 ± 0.40 and length of 4.11 ± 0.23 cm, after 4 wk of incubation. The micropropagated plantlets were successfully acclimatized and hardened off in Soilrite™ with a 90% survival rate. The plantlets grew well with normal growth, flowering and showed, by gas chromatography–mass spectroscopy, an increase in the number of bioactive compounds compared with the donor plant. This is the first report on T. stans in vitro regeneration using TDZ.