Insecticidal and Enzyme Inhibition Activities of Leaf/Bark Extracts, Fractions, Seed Oil and Isolated Compounds from Triadica sebifera (L.) Small against Aphis craccivora Koch.

Aphid, Aphis craccivora Koch (Hemiptera: Aphididae), is a major sap-sucking insect pest of leguminous crops and also transmits plant viruses, leading to economic yield loss. Indiscriminate and repeated use of insecticides for control of aphid leads to the development of resistance, and is harmful to the environment, non-target organisms, etc. Plant-based extracts/seed oils (SO) are the best alternatives to insecticides. Insecticidal activities of Triadica sebifera have not been reported against A. craccivora and other insect pests to date. In the current study, the main objective was to study the insecticidal activities of leaf/bark extracts/fractions, seed oil, isolated compounds, and their combinations against A. craccivora. Results showed that, among the extracts, ethanolic bark extract 80% (LC50 = 5115.98 mg/L) was more effective against A. craccivora. Among fractions, the n-hexane fraction of leaves (LC50 = 425.73 mg/L) and the ethyl acetate fraction of bark (LC50 = 813.45 mg/L) were promising. Among compounds, gallic acid was the most effective (LC50 = 1303.68 mg/L) compared to shikimic acid and quercetin. SO (LC50 = 850.94 mg/L) was superior compared to extracts/fractions/compounds. All the combinations showed toxicity and synergistic activity. Leaf/bark extracts and SO significantly inhibited the AChE and GST activity in A. craccivora. Based on field bio-efficacy, the leaf extract/SO or their combinations can be recommended for the control of aphids.

Sesquineolignan and neolignan enantiomers from Triadica sebifera.

Two pairs of new sesquineolignan enantiomers (1a/1b and 1c/1d), two pair of new 4',7-epoxy-8,3'-neolignan enantiomers (2a/2b and 3a/3b), and a pair of new 3',7-epoxy-8,4'-oxyneolignan enantiomers (4a/4b), along with two pairs of known 4',7-epoxy-8,3'-neolignan enantiomers (5a/5b and 6a/6b), were obtained from the stems and leaves of Triadica sebifera. The structures of the enantiomers were elucidated by spectroscopic analyses, and their absolute configurations were assigned by the experimental ECD spectra. Among them, compounds 5b, 6a and 6b showed inhibitory activities against NO production in activated microglial BV-2 cells, with IC50 values of 14.3, 23.2 and 33.3 µM, respectively.

Deep Sequencing of the Fruit Transcriptome and Lipid Accumulation in a Non-Seed Tissue of Chinese Tallow, a Potential Biofuel Crop.

Chinese tallow (Triadica sebifera) is a valuable oilseed-producing tree that can grow in a variety of conditions without competing for food production, and is a promising biofuel feedstock candidate. The fruits are unique in that they contain both saturated and unsaturated fat present in the tallow and seed layer, respectively. The tallow layer is poorly studied and is considered only as an external fatty deposition secreted from the seed. In this study we show that tallow is in fact a non-seed cellular tissue capable of triglyceride synthesis. Knowledge of lipid synthesis and storage mechanisms in tissues other than seed is limited but essential to generate oil-rich biomass crops. Here, we describe the annotated transcriptome assembly generated from the fruit coat, tallow and seed tissues of Chinese tallow. The final assembly was functionally annotated, allowing for the identification of candidate genes and reconstruction of lipid pathways. A tallow tissue-specific paralog for the transcription factor gene WRINKLED1 (WRI1) and lipid droplet-associated protein genes, distinct from those expressed in seed tissue, were found to be active in tallow, underpinning the mode of oil synthesis and packaging in this tissue. Our data have established an excellent knowledge base that can provide genetic and biochemical insights for engineering non-seed tissues to accumulate large amounts of oil. In addition to the large data set of annotated transcripts, the study also provides gene-based simple sequence repeat and single nucleotide polymorphism markers.

A native plant competitor mediates the impact of above- and belowground damage on an invasive tree.

Plant competition may mediate the impacts of herbivory on invasive plant species through effects on plant growth and defense. This may predictably depend on whether herbivory occurs above or below ground and on relative plant competitive ability. We simulated the potential impact of above- or belowground damage by biocontrol agents on the growth of a woody invader (Chinese tallow tree, Triadica sebifera) through artificial herbivory, with or without competition with a native grass, little bluestem (Schizachyrium scoparium). We measured two defense responses of Triadica through quantifying constitutive and induced extrafloral nectar production and tolerance of above- and belowground damage (root and shoot biomass regrowth). We examined genetic variation in plant growth and defense across native (China) and invasive (United States) Triadica populations. Without competition, aboveground damage had a greater impact than belowground damage on Triadica performance, whereas with competition and above- and belowground damage impacted Triadica similarly. Whole plant tolerance to damage below ground was negatively associated with tolerance to grass competitors indicating tradeoffs in the ability to tolerate herbivory vs. compete. Competition reduced investment in defensive extrafloral nectar (EFN) production. Aboveground damage inhibited rather than induced EFN production while belowground plant damage did not impact aboveground nectar production. We found some support for the evolution of increased competitive ability hypothesis for invasive plants as United States plants were larger than native China plants and were more plastic in their response to biotic stressors than China plants (they altered their root to shoot ratios dependent on herbivory and competition treatments). Our results indicate that habitat type and the presence of competitors may be a larger determinant of herbivory impact than feeding mode and suggest that integrated pest management strategies including competitive dynamics of recipient communities should be incorporated into biological control agent evaluation at earlier stages.

Plant genotypes affect aboveground and belowground herbivore interactions by changing chemical defense.

Spatially separated aboveground (AG) and belowground (BG) herbivores are closely linked through shared host plants, and both patterns of AG-BG interactions and plant responses may vary among plant genotypes. We subjected invasive (USA) and native (China) genotypes of tallow tree (Triadica sebifera) to herbivory by the AG specialist leaf-rolling weevil Heterapoderopsis bicallosicollis and/or the root-feeding larvae of flea beetle Bikasha collaris. We measured leaf damage and leaves rolled by weevils, quantified beetle survival, and analyzed flavonoid and tannin concentrations in leaves and roots. AG and BG herbivores formed negative feedbacks on both native and invasive genotypes. Leaf damage by weevils and the number of beetle larvae emerging as adults were higher on invasive genotypes. Beetles reduced weevil damage and weevils reduced beetle larval emergence more strongly for invasive genotypes. Invasive genotypes had lower leaf and root tannins than native genotypes. BG beetles decreased leaf tannins of native genotypes but increased root tannins of invasive genotypes. AG herbivory increased root flavonoids of invasive genotypes while BG herbivory decreased leaf flavonoids. Invasive genotypes had lower AG and BG herbivore resistance, and negative AG-BG herbivore feedbacks were much stronger for invasive genotypes. Lower tannin concentrations explained overall better AG and BG herbivore performances on invasive genotypes. However, changes in tannins and flavonoids affected AG and BG herbivores differently. These results suggest that divergent selection on chemical production in invasive plants may be critical in regulating herbivore performances and novel AG and BG herbivore communities in new environments.

Below-ground herbivory limits induction of extrafloral nectar by above-ground herbivores.

BACKGROUND AND AIMS: Many plants produce extrafloral nectar (EFN), and increase production following above-ground herbivory, presumably to attract natural enemies of the herbivores. Below-ground herbivores, alone or in combination with those above ground, may also alter EFN production depending on the specificity of this defence response and the interactions among herbivores mediated through plant defences. To date, however, a lack of manipulative experiments investigating EFN production induced by above- and below-ground herbivory has limited our understanding of how below-ground herbivory mediates indirect plant defences to affect above-ground herbivores and their natural enemies. METHODS: In a greenhouse experiment, seedlings of tallow tree (Triadica sebifera) were subjected to herbivory by a specialist flea beetle (Bikasha collaris) that naturally co-occurs as foliage-feeding adults and root-feeding larvae. Seedlings were subjected to above-ground adults and/or below-ground larvae herbivory, and EFN production was monitored. KEY RESULTS: Above- and/or below-ground herbivory significantly increased the percentage of leaves with active nectaries, the volume of EFN and the mass of soluble solids within the nectar. Simultaneous above- and below-ground herbivory induced a higher volume of EFN and mass of soluble solids than below-ground herbivory alone, but highest EFN production was induced by above-ground herbivory when below-ground herbivores were absent. CONCLUSIONS: The induction of EFN production by below-ground damage suggests that systemic induction underlies some of the EFN response. The strong induction by above-ground herbivory in the absence of below-ground herbivory points to specific induction based on above- and below-ground signals that may be adaptive for this above-ground indirect defence.

Genetic Analysis and Construction of a Fingerprint for Licensed Triadica sebifera Cultivars Using SSR Markers.

Triadica sebifera is an important landscaping tree species because of its colorful autumn leaves. In recent years, some cultivars have been bred and licensed, but it can be difficult to identify them from their morphological traits due to their similar phenotypes. To explore the genetic relationships and construct a fingerprint of the cultivars, the licensed T. sebifera cultivars were analyzed using SSR markers. A total of 179 alleles were identified among the 21 cultivars at 16 SSR loci, and these alleles exhibited a high level of genetic diversity (He = 0.86). The genetic variations mainly occurred among cultivars based on an analysis of molecular variance (AMOVA). According to phylogenetic analysis, principal coordinate analysis (PCoA), and Bayesian clustering analysis, the genetic relationships were independent of geographic distances, which may be mainly due to transplantations between regions. Some cultivars with different leaf colors showed obvious genetic differentiation and may be preliminary candidates for cross-breeding. Finally, the fingerprint for the licensed cultivars was constructed with two SSR markers. The results of this study can provide technical support for the application and legal protection of licensed Triadica sebifera cultivars.

Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores.

To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and below-ground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal above-ground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and below-ground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics.

Specificity of extrafloral nectar induction by herbivores differs among native and invasive populations of tallow tree.

BACKGROUND AND AIMS: Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, few studies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage. METHODS: Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallow tree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production. KEY RESULTS: Plants from introduced populations had more leaves producing constitutive EFN than did native populations, but the content of soluble solids of EFN did not differ. Herbivores induced EFN production more than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (2·1 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations. CONCLUSIONS: These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants.

Shift of Host Range for the Immature Stages of the Lanternfly, Pyrops watanabei (Matsumura) (Hemiptera, Fulgoridae) Native to Taiwan.

Although Pyrops watanabei is a species native to Taiwan, many fundamental aspects of the species are still poorly documented. Populations of the lanternfly in locations of northern Taiwan were found in abundance and were suitable for the conduction of an investigation from 1 July 2021 to 30 June 2022. We established the shift in the main host plants with different developmental stages. The occurrence of immature individuals on Heptapleurum heptaphyllum increased with age from eggs to nymphs in the third instar; however, it declined from the fourth instar onwards due to a shift in preference to Triadica sebifera. In 2021, the earliest detection of an egg mass was on 1 July. More eggs were recorded in August, and some could be found in September and October of the same year. In 2022, we found an egg mass on 28 June. In August 2021, nymphs in the first and second instars were detected. Then, nymphs in the third and fourth instars appeared after September and October 2021, respectively. Furthermore, nymphs in the fifth instar were sighted as late as March 2022. Finally, this study will provide a basis for further evaluation of the impact of invasion of Pyrops candelaria on the ecology of Pyrops watanabei.

Foliar Herbivory Reduces Rhizosphere Fungal Diversity and Destabilizes the Co-occurrence Network.

Insect herbivores can adversely impact terrestrial plants throughout ontogeny and across various ecosystems. Simultaneously, the effects of foliar herbivory may extend belowground, to the soil microbial community. However, the responses in terms of the diversity, assembly, and stability of rhizosphere fungi to aboveground herbivory remain understudied. Here, using high-throughput sequencing, the effects of foliar insect herbivory on rhizosphere fungal microbes were investigated in a common garden experiment that manipulated herbivory intensity and time from herbivore removal. The number of observed fungal species was reduced by a greater herbivory intensity, with some species evidently sensitive to herbivory intensity and time since herbivore removal. Rhizofungal assembly processes were altered by both herbivory intensity and time since herbivore removal. Further, we found evidence that both factors strongly influenced fungal community stability: a high intensity of herbivory coupled with a shorter time since herbivore removal resulted in low stability. These results suggest that foliar herbivory can adversely alter fungal diversity and stability, which would in turn be harmful for plant health. Fortunately, the effect seems to gradually diminish with time elapsed after herbivore removal. Our findings provide a fresh, in-depth view into the roles of rhizofungi in enhancing the adaption ability of plants under environmental stress.

Host Plants of the Immature Stages of the Invasive Longan Lanternfly, Pyrops candelaria (L.) (Hemiptera, Fulgoridae) in Taiwan.

The longan lanternfly, Pyrops candelaria (L.), has been invading mainland Taiwan since 2018, but the distribution of the species has been confined to northern Taiwan until now. The manual removal of the adult insects from the longan is still the main control strategy because of the uncertainty around other key host plants, especially for eggs and nymphs. In this study, large numbers of eggs and nymphs were found on Triadica sebifera (L.) Small and Acacia confusa Merr. The occurrence of immature individuals on Triadica sebifera increased with developmental stage from eggs to the last instar from May to July 2021. On 30 April, the first egg mass was recorded. More egg masses were recorded in May, and some could be found in July. In May, only two younger instars were detected. Third and fourth instars began to appear from June, while the fifth instar was mainly recorded from July onwards. The results of this study provide great strategic value for decision-makers to allow for effective control of the target tree species. For now, we proved that longan and pomelo trees, preferred by adults, are not the key hosts for the immature stages of this insect, because few immature individuals were found on them. Therefore, we suggest that the existence of Triadica sebifera should be considered when analyzing possible spreading areas of this invasive lanternfly in Taiwan.

Impact of Field Densities of the Naturalized Defoliator Caloptilia triadicae (Lepidoptera: Gracillariidae) on the Invasive Weed Chinese Tallowtree.

Chinese tallowtree, Triadica sebifera (L.) Small (Euphoriaceae), is one of the most aggressive weeds of coastal wetlands and forests of the southeastern United States. The lack of specialist herbivores in the invaded range may be one of the factors that contribute to the invasive nature of this weed. Chinese tallowtree has been the target of a classical biological control project since 2006. Several herbivore species are being tested for biological control of Chinese tallowtree. Concurrently, an adventive herbivore, Caloptilia triadicae Davis (Lepidoptera: Gracillariidae), was found feeding on Chinese tallowtree in the southeastern United States in 2004 and now occurs throughout the invaded range. Field populations of C. triadicae from two sites caused extensive mining damage to the Chinese tallowtree leaves. The greatest damage occurred after 30 d of exposure to C. triadicae in the herbivory treatment and amounted to about 25-30 leaf mines (early instars) and leaf rolls (late instars) per plant. Insecticide-treated plants had atmost 5-10 leaf mines and rolls per plant. Despite this difference, plant growth in height, number of new branches, and leaves did not differ significantly from plants protected from herbivory. Analysis of harvested plant results suggested that, in general, herbivory had little impact on biomass. However, there was a slight reduction in trunk weights in the unrestriced herbivory treatment compared with the insecticide-treated plants. Although this study exposed experimental plants to only 60 d of herbivory, these results suggested that C. triadicae alone will not exert sufficient control of invasive populations of Chinese tallowtree. Furthermore, they indicated that continued development of biological control agents that target Chinese tallowtree are needed.

Comparative Lipidomics and Proteomics of Lipid Droplets in the Mesocarp and Seed Tissues of Chinese Tallow (Triadica sebifera).

Lipid droplets (LDs) are composed of a monolayer of phospholipids (PLs), surrounding a core of non-polar lipids that consist mostly of triacylglycerols (TAGs) and to a lesser extent diacylglycerols. In this study, lipidome analysis illustrated striking differences in non-polar lipids and PL species between LDs derived from Triadica sebifera seed kernels and mesocarp. In mesocarp LDs, the most abundant species of TAG contained one C18:1 and two C16:0 and fatty acids, while TAGs containing three C18 fatty acids with higher level of unsaturation were dominant in the seed kernel LDs. This reflects the distinct differences in fatty acid composition of mesocarp (palmitate-rich) and seed-derived oil (α-linoleneate-rich) in T. sebifera. Major PLs in seed LDs were found to be rich in polyunsaturated fatty acids, in contrast to those with relatively shorter carbon chain and lower level of unsaturation in mesocarp LDs. The LD proteome analysis in T. sebifera identified 207 proteins from mesocarp, and 54 proteins from seed kernel, which belong to various functional classes including lipid metabolism, transcription and translation, trafficking and transport, cytoskeleton, chaperones, and signal transduction. Oleosin and lipid droplets associated proteins (LDAP) were found to be the predominant proteins associated with LDs in seed and mesocarp tissues, respectively. We also show that LDs appear to be in close proximity to a number of organelles including the endoplasmic reticulum, mitochondria, peroxisomes, and Golgi apparatus. This comparative study between seed and mesocarp LDs may shed some light on the structure of plant LDs and improve our understanding of their functionality and cellular metabolic networks in oleaginous plant tissues.

An experimental test of the EICA Hypothesis in multiple ranges: invasive populations outperform those from the native range independent of insect herbivore suppression.

The success of invasive plants may reflect environmental differences in their native and introduced ranges including both abiotic and biotic conditions, such as release from aboveground herbivory. However, in response to these novel conditions, plants from invasive populations may have higher growth rates and lower defense levels compared to those in the native range. This may contribute to their success in the introduced range but perhaps not in the native range. Here, we grew 1000 Triadica sebifera plants from 14 native and introduced populations in seven common gardens with unmanaged background vegetation for three growing seasons in three geographic venues that varied in T. sebifera status and insect herbivore communities: Texas -T. sebifera is invasive, low levels of generalist herbivory; Hawaii - T. sebifera introduced but not invasive, high levels of generalist herbivory from exotic herbivores; China - native range, both generalist and specialist herbivores. We suppressed aboveground insects with insecticide on half the plants. Aboveground damage in the first growing season was lowest in Texas and insecticide sprays reduced damage in China. At the end of the first growing season, plants were tallest on average in China and shortest in Hawaii. However, height in later years and mass were highest on average in Texas and lowest in Hawaii. However, there was large variation in damage and plant performance among gardens within venues. Our results suggest that more rapid aboveground growth rates contribute to T. sebifera's success in both the invasive and native ranges independent of aboveground herbivory. However, strong variation among sites indicates that T. sebifera plants from invasive populations only have a strong advantage in a subset of sites in Texas.

In-situ transesterification of seeds of invasive Chinese tallow trees (Triadica sebifera L.) in a microwave batch system (GREEN(3)) using hexane as co-solvent: Biodiesel production and process optimization.

In-situ transesterification (simultaneous extraction and transesterification) of Chinese tallow tree seeds into methyl esters using a batch microwave system was investigated in this study. A high degree of oil extraction and efficient conversion of oil to biodiesel were found in the proposed range. The process was further optimized in terms of product yields and conversion rates using Doehlert optimization methodology. Based on the experimental results and statistical analysis, the optimal production yield conditions for this process were determined as: catalyst concentration of 1.74wt.%, solvent ratio about 3 (v/w), reaction time of 20min and temperature of 58.1°C. H(+)NMR was used to calculate reaction conversion. All methyl esters produced using this method met ASTM biodiesel quality specifications.