Harmful self-pollination drives gynodioecy in European chestnut, a self-incompatible tree.

PREMISE: Gynodioecy is a rare sexual system in which two genders (sensu Lloyd, 1980), cosexuals and females, coexist. To survive, female plants must compensate for their lack of siring capacity and male attractiveness. In European chestnut (Castanea sativa), an outcrossing tree, self-pollination reduces fruit set in cosexual individuals because of late-acting self-incompatibility and early inbreeding depression. Could this negative sexual interaction explain the presence of females in this species? METHODS: We studied gender variation in wild populations of European chestnut. In addition, we compared fruit set (the proportion of flowers giving fruits) and other key female fitness components as well as reproductive allocation between genders. We then performed emasculation experiments in cosexual trees, by removing nectar-producing fertile male inflorescences. We also removed sterile but nectar-producing male inflorescences from female trees, as a control. RESULTS: We found a highly variable proportion of male-sterile individuals in the wild in European chestnut. In the experimental plot, trees from each gender had similar size, flower density, and burr set, but different fruit set. Removing nectar-producing male inflorescences from branches or entire trees increased fruit set in cosexual but not in female trees. CONCLUSIONS: These results show that self-pollination impairs fruit set in cosexual trees. Female trees avoid these problems as they do not produce pollen but continue to attract pollinators thanks to their rewarding male-sterile inflorescences, resulting in a much higher fruit set than in cosexuals. This demonstrates that even outcrossed plants can benefit from the cessation of self-pollination, to the point that unisexuality can evolve.

Isolation of Hydrolyzable Tannins from Castanea sativa Using Centrifugal Partition Chromatography.

Castanea sativa wood is a rich source of hydrolyzable tannins, known for their diverse bioactivities. To investigate these bioactive properties further, it is crucial to isolate and characterize hydrophilic compounds effectively. To address this issue, we developed a centrifugal partition chromatography (CPC) method and applied it to an aqueous C. sativa wood extract. We determined the partition coefficients (KD) of the six major compounds using four butanol-/water-based biphasic solvent systems. Initially, we utilized the n-butanol/propanol/water (3:1:4, v/v/v) systems for the first fractionation step. Subsequently, we employed the water/methyl tert-butyl ether/butanol/acetone (8:5:3:4, v/v/v/v) system to fractionate moderately and highly hydrophilic fractions. We calculated the KD values for major compounds of the most hydrophilic fractions using the butanol/ethanol/water (4:1:5, v/v/v) and butanol/isopropanol/water (2:1:3, v/v/v) systems. In total, we isolated 23 compounds through a combination of CPC, size exclusion chromatography, and preparative HPLC. Among these compounds, six have never been previously described. We characterized them by 1D and 2D NMR experiments and high-resolution mass spectroscopy acquisitions.

Genome-Wide Characterization and Functional Validation of the ACS Gene Family in the Chestnut Reveals Its Regulatory Role in Ovule Development.

Ovule abortion significantly contributes to a reduction in chestnut yield. Therefore, an examination of the mechanisms underlying ovule abortion is crucial for increasing chestnut yield. In our previous study, we conducted a comprehensive multiomic analysis of fertile and abortive ovules and found that ACS genes in chestnuts (CmACS) play a crucial role in ovule development. Therefore, to further study the function of ACS genes, a total of seven CmACS members were identified, their gene structures, conserved structural domains, evolutionary trees, chromosomal localization, and promoter cis-acting elements were analyzed, and their subcellular localization was predicted and verified. The spatiotemporal specificity of the expression of the seven CmACS genes was confirmed via qRT-PCR analysis. Notably, CmACS7 was exclusively expressed in the floral organs, and its expression peaked during fertilization and decreased after fertilization. The ACC levels remained consistently greater in fertile ovules than in abortive ovules. The ACSase activity of CmACS7 was identified using the genetic transformation of chestnut healing tissue. Micro Solanum lycopersicum plants overexpressing CmACS7 had a significantly greater rate of seed failure than did wild-type plants. Our results suggest that ovule fertilization activates CmACS7 and increases ACC levels, whereas an overexpression of CmACS7 leads to an increase in ACC content in the ovule prior to fertilization, which can lead to abortion. In conclusion, the present study demonstrated that chestnut ovule abortion is caused by poor fertilization and not by nutritional competition. Optimization of the pollination and fertilization of female flowers is essential for increasing chestnut yield and reducing ovule abortion.

Investigation into the Anti-Acne Effects of Castanea sativa Mill Leaf and Its Pure Ellagitannin Castalagin in HaCaT Cells Infected with Cutibacterium acnes.

Acne vulgaris is a prevalent skin disorder affecting many young individuals, marked by keratinization, inflammation, seborrhea, and colonization by Cutibacterium acnes (C. acnes). Ellagitannins, known for their antibacterial and anti-inflammatory properties, have not been widely studied for their anti-acne effects. Chestnut (Castanea sativa Mill., C. sativa), a rich ellagitannin source, including castalagin whose acne-related bioactivity was previously unexplored, was investigated in this study. The research assessed the effect of C. sativa leaf extract and castalagin on human keratinocytes (HaCaT) infected with C. acnes, finding that both inhibited IL-8 and IL-6 release at concentrations below 25 µg/mL. The action mechanism was linked to NF-κB inhibition, without AP-1 involvement. Furthermore, the extract displayed anti-biofilm properties and reduced CK-10 expression, indicating a potential role in mitigating inflammation, bacterial colonization, and keratosis. Castalagin's bioactivity mirrored the extract's effects, notably in IL-8 inhibition, NF-κB inhibition, and biofilm formation at low µM levels. Other polyphenols, such as flavonol glycosides identified via LC-MS, might also contribute to the extract's biological activities. This study is the first to explore ellagitannins' potential in treating acne, offering insights for developing chestnut-based anti-acne treatments pending future in vivo studies.

Distribution, causal agents, and infection dynamic of emerging ink disease of sweet chestnut in Southern Switzerland.

Emerging diseases caused by both native and exotic pathogens represent a main threat to forest ecosystems worldwide. The two invasive soilborne pathogens Phytophthora cinnamomi and Phytophthora × cambivora are the causal agents of ink disease, which has been threatening Castanea sativa in Europe for several centuries and seems to be re-emerging in recent years. Here, we investigated the distribution, causal agents, and infection dynamics of ink disease in southern Switzerland. A total of 25 outbreaks were identified, 19 with only P. cinnamomi, 5 with only P. × cambivora, and 1 with both species. Dendrochronological analyses showed that the disease emerged in the last 20-30 years. Infected trees either died rapidly within 5-15 years post-infection or showed a prolonged state of general decline until death. Based on a generalized linear model, the local risk of occurrence of ink disease was increased by an S-SE aspect of the chestnut stand, the presence of a pure chestnut stand, management activities, the proximity of roads and buildings, and increasing annual mean temperature and precipitation. The genetic structure of the local P. cinnamomi population suggests independent introductions and local spread of the pathogen.

The fertilization process in Lithocarpus dealbatus (Fagaceae) and its implication on the sexual reproduction evolution of Fagales.

MAIN CONCLUSION: The pistillate flowers of Lithocarpus dealbatus show two pollen tube (PT) arresting sites (the style-joining and micropyle) within the pistil during the postpollination-prezygotic stage. The PT, arrested at the pre-ovule stage, enhanced PT competition allowing the most compatible PTs to enter the ovary to ensure the highest fertilization success. During the shift from animal pollination to wind pollination, plants require a series of changes in reproductive traits. The mode of pollination is striking labile in Fagaceae. Lithocarpus is insect pollinated and is closely related to wind-pollinated Quercus. Little is known about the sexual reproduction of Lithocarpus. This study aimed to reveal the sexual reproduction of Lithocarpus dealbatus and to explore the evolutionary pattern of the key sexual reproduction traits to better understand their possible role in labile pollination. We found that after pollination, L. dealbatus PTs grew slowly in the style reaching style-joining in mid-January of the second year; then PT growth was arrested at style-joining for four months. Only two to three PTs resumed growth in mid-May to reach the micropyle, where PT growth ceased for one month before one PT resumed growth and passed through the micropyle to the embryo sac. Fagaceae showed a generalized mating system. Vast pollen production, small-sized pollen grains, long stigmatic receptive time, and reduced perianth were compatible with beetle pollination syndrome, representing the plesiomorphic status in Fagaceae. A large stigmatic surface and dry pollen grains linked to wind pollination might be independently derived several times in fagaceous lineages. Beetle pollination syndrome can cope with the uncertainty of pollinators to ensure conspecific pollen capture, which represents pre-adaptation status and has a selective advantage when conditions change, favouring wind pollination. The arrest of the PT at style-joining is a unique mechanism in later derived fagaceous lineages to enhance PT competition and promote outcrossing.

Use of retrotransposon based iPBS markers for determination of genetic relationship among some Chestnut Cultivars (Castanea sativa Mill.) in Türkiye.

BACKGROUND: The aim of this study was to reveal the genetic relationships among some economically important chestnut cultivars for Türkiye by using retrotransposon-based inter primer binding site (iPBS) markers. METHODS AND RESULTS: In this study, a total of 19 iPBS markers were used to determine the genetic relationships among 11 chestnut cultivars (Castanea sativa Mill.). In the study, chestnut cultivars named Haciömer, Osmanoglu, Sariaslama, Erfelek, Kemer, Isiklar, Sekerci, Siyah Bursa, Tülü, Bouche De Betizac and Marigoule were the preferred cultivars utilised. Using the online marker efficiency calculator (iMEC), some indices of polymorphism, such as the mean heterozygosity, polymorphism information content, marker index and discriminating power, were determined. In addition, the size ranges of alleles, number of average alleles, number of total alleles, number of polymorphic alleles, and polymorphism rate were determined at a successful level. The chestnut cultivars of Haciömer and Sekerci were determined to be the most similar cultivars with a similarity coefficient value of 0.924, and they formed a subgroup together with the chestnut cultivars Osmanoglu and Erfelek, showing close similarity with these two cultivars. CONCLUSIONS: The use of iPBS markers in chestnuts in Türkiye was carried out for the first time in this study. The power of iPBS markers to evaluate the genetic relationship for our preferred chestnut cultivars was revealed. For this reason, it has emerged that it will be useful in the molecular characterization of both genotypes in natural chestnut populations and chestnut breeding materials such as varieties and cultivars in chestnut breeding programs.

The Fungal Pathogen Gnomoniopsis castaneae Induces Damaging Cankers in Multiple Domestic Fagaceae Species.

Gnomoniopsis castaneae is internationally recognized as a destructive pathogen of chestnut species. Primarily associated with nut rot, it has also been associated with branch and stem cankers of chestnut and as an endophyte of multiple additional hardwood species. The present study evaluated implications of the recently reported United States presence of the pathogen for domestic Fagaceae species. Stem inoculation assays of Castanea dentata, C. mollissima, C. dentata × C. mollissima, and Quercus rubra (red oak) seedlings were utilized to examine the cankering ability of a regional isolate of the pathogen. The pathogen induced damaging cankers in all assessed species and significant stem girdling in all chestnut species. No previous study has associated the pathogen with damaging infection in Quercus species, and its presence in the United States has the potential to compound ongoing chestnut recovery programs and oak regeneration problems within forest systems.

Auxin and CmAP1 regulate the reproductive development of axillary buds in Chinese chestnut (Castanea mollissima).

KEY MESSAGE: Auxin accumulation upregulates the expression of APETALA1 (CmAP1) and subsequently activates inflorescence primordium development in axillary buds of chestnut. The architecture of fruiting branches is a key determinant of chestnut yield. Normally, axillary buds at the top of mother fruiting branches develop into flowering shoots and bear fruits, and the lower axillary buds develop into vegetative shoots. Decapitation of the upper axillary buds induces the lower buds to develop into flowering shoots. How decapitation modulates the tradeoff between vegetative and reproductive development is unclear. We detected inflorescence primordia within both upper and lower axillary buds on mother fruiting branches. The level of the phytohormones 3-indoleacetic acid (IAA) and trans-zeatin (tZ) increased in the lower axillary buds in response to decapitation. Exogenous application of the synthetic analogues 1-naphthylacetic acid (NAA) or 6-benzyladenine (6-BA) blocked or promoted, respectively, the development of the inflorescence primordia in axillary buds. The transcript levels of the floral identity gene CmAP1 increased in axillary buds following decapitation. An auxin response element TGA-box is present in the CmAP1 promoter and influenced the CmAP1 promoter-driven expression of ß-glucuronidase (GUS) in floral organs in Arabidopsis, suggesting that CmAP1 is induced by auxin. We propose that decapitation releases axillary bud outgrowth from inhibition caused by apical dominance. During this process, decapitation-induced accumulation of auxin induces CmAP1 expression, subsequently promoting the reproductive development of axillary buds.

Utilization of Response Surface Methodology in Optimization of Proline Extraction from Castanea sativa Honey.

Proline constitutes approximately 85 % of the amino acid composition of honey. Therefore, the quantitative determination of this amino acid in honey samples is used by many national/international authorities to evaluate the quality of honey types. In this study, it was aimed to achieve maximum proline amino acid extraction from honey samples whose botanical origins were confirmed by melissopalynological analysis. For this reason, based on three different spectrophotometric methods used in the literature for proline analysis, proline extraction was optimized with the Response Surface Method (RSM) and Box-Behnken experimental design. Three independent variables were determined as treatment time (2, 6, and 10 min), treatment temperature (22, 46, and 70 °C), and cooling time (5, 25, and 45 min). As a result of the optimization, it was seen that only significantly effective independent variable on the proline content of honey was the processing temperature. The optimum conditions obtained as a result of the RSM were found to be 2 min for the treatment time, 70 °C for the treatment temperature and 45 min for the cooling time. The composite desirability of the optimum conditions (R2 ) was found to be 1.00. It was determined that the method proposed by International Honey Commission (IHC) is efficient for proline analysis, but it provides more proline extraction by reducing of time from 10 min to 2 min in hold time in boiling water bath only during the extraction step. As a result, the conditions to be used in order to achieve maximum proline extraction with different spectrophotometric methods were determined and optimum values were determined. In addition, since the botanical origin of honey samples significantly affects the proline content of honey, it can be suggested that this study be optimized for different monofloral honey samples as well.

Validation of an Alternative Small Stem Assay for Blight Resistance in Chestnut Seedlings and Recommendations for Broader Use.

We evaluated an alternative small stem assay (AltSSA) for blight resistance in backcross hybrid chestnut trees (Castanea dentata/mollissima). Whereas standard small stem assays (SSAs) are done by inoculating small incisions in stems, in our AltSSA, 4- to 5-mm stems are cut off, and the exposed (living) stem tips are inoculated with discs of Cryphonectria parasitica inoculum and temporarily covered with plastic sleeves. Intended primarily for forward selection, this method was designed to be easy to implement, to consistently induce cankering, and to better enable seedling recovery via the development of lateral shoots from the lower stem. After 90+ days, cankers are evaluated and removed, and seedlings are prepared for out-planting. Previous results showed that AltSSAs performed at least as well as a common SSA method in distinguishing resistant and susceptible types. In this follow-up analysis of 35 lines of backcross seedlings studied in 2020 and 2021, we showed that mean orange zone canker length (OZCL) and a multifactor principal components analysis-based blight resistance index gave results consistent with predictions derived from two methods of blight resistance phenotyping and percentage of American chestnut ancestry of the parents of each line. As expected, based upon the apparent polygenic inheritance of blight resistance in backcross chestnut trees, mean OZCL of backcross families ranged from intermediate (F1 hybrid-level) to low (wild-type American chestnut-level). Consistent with prior results, canker production was near 100%, survivorship after out-planting was very high, and postinoculation stem dieback was not apparently related to the stem tip inoculations. Altogether, these results suggest that the AltSSA is a viable method for early detection of relative blight resistance in seedlings and may enable a reduction in the numbers of trees out-planted and placed under care for long-term evaluation and breeding. Thus, the AltSSA can prevent time, resources, and orchard space from being used on susceptible trees.

Identification and Quantification of the Major Phenolic Constituents in Castanea sativa and Commercial Interspecific Hybrids (C. sativa x C. crenata) Chestnuts Using HPLC-MS/MS.

Due to the lack of studies on chestnut metabolites, this study was conducted to identify and quantify the major phenolic constituents in chestnuts. Data were compared with the three most commonly grown interspecific hybrids of C. sativa and C. crenata ('Bouche de Betizac', 'Marsol', and 'Maraval') and three "native" accessions of C. sativa. High-performance liquid chromatography coupled with mass spectrometry was used to identify and quantify these compounds. Four dicarboxylic acid derivatives, five hydroxybenzoic acids, nine hydroxycinnamic acids, and three flavanols were identified and quantified, most of them for the first time. Hydroxybenzoic acids were the major phenolic compounds in all chestnut cultivars/accessions, followed by flavanols, dicarboxylic acid derivatives, and hydroxycinnamic acids. Of all the compounds studied, the (epi)catechin dimer was the most abundant in chestnut. The assumption that cultivars from commercial hybrids have a better and different metabolic profile than "native" accessions was refuted.

Proanthocyanins and anthocyanins in chestnut (Castanea mollissima) shell extracts: biotransformation in the simulated gastrointestinal model and interaction with gut microbiota in vitro.

BACKGROUND: Chestnut (Castanea mollissima) shell is rich in flavonoids and our previous studies showed that proanthocyanins and anthocyanins were the two markedly varied flavonoids in chestnut shell extracts (CSE) during digestion. Here, the biotransformation of proanthocyanins and anthocyanins in a simulated gastrointestinal model, and the interactions between non-absorption CSE (NACSE) and gut microbiota in vitro, were investigated by ultra-high-performance liquid chromatography combined with triple-quadrupole mass spectrometry and 16S rRNA sequencing. RESULTS: Chestnut shell was richer in proanthocyanins and anthocyanins, while the loss of proanthocyanins was greater after digestion. Additionally, the content of anthocyanin decreased after gastric digestion but increased after intestinal digestion and remained stable after fermentation. After fermentation, delphinidin-3-O-sambubioside and pelargonidin-3-O-galactoside were newly formed. Furthermore, microbiome profiling indicated that NACSE promoted the proliferation of beneficial bacteria, while inhibiting pathogenic bacteria. CONCLUSION: All these data suggest that CSE may be a promising candidate to protect gut health. © 2023 Society of Chemical Industry.

In-Tree Behavior of Diverse Viruses Harbored in the Chestnut Blight Fungus, Cryphonectria parasitica.

The ascomycete Cryphonectria parasitica causes destructive chestnut blight. Biological control of the fungus by virus infection (hypovirulence) has been shown to be an effective control strategy against chestnut blight in Europe. To provide biocontrol effects, viruses must be able to induce hypovirulence and spread efficiently in chestnut trees. Field studies using living trees to date have focused on a selected family of viruses called hypoviruses, especially prototypic hypovirus CHV1, but there are now known to be many other viruses that infect C. parasitica Here, we tested seven different viruses for their hypovirulence induction, biocontrol potential, and transmission properties between two vegetatively compatible but molecularly distinguishable fungal strains in trees. The test included cytosolically and mitochondrially replicating viruses with positive-sense single-stranded RNA or double-stranded RNA genomes. The seven viruses showed different in planta behaviors and were classified into four groups. Group I, including CHV1, had great biocontrol potential and could protect trees by efficiently spreading and converting virulent to hypovirulent cankers in the trees. Group II could induce high levels of hypovirulence but showed much smaller biocontrol potential, likely because of inefficient virus transmission. Group III showed poor performance in hypovirulence induction and biocontrol, while efficiently being transmitted in the infected trees. Group IV could induce hypovirulence and spread efficiently but showed poor biocontrol potential. Nuclear and mitochondrial genotyping of fungal isolates obtained from the treated cankers confirmed virus transmission between the two fungal strains in most isolates. These results are discussed in view of dynamic interactions in the tripartite pathosystem.IMPORTANCE The ascomycete Cryphonectria parasitica causes destructive chestnut blight, which is controllable by hypovirulence-conferring viruses infecting the fungus. The tripartite chestnut/C. parasitica/virus pathosystem involves the dynamic interactions of their genetic elements, i.e., virus transmission and lateral transfer of nuclear and mitochondrial genomes between fungal strains via anastomosis occurring in trees. Here, we tested diverse RNA viruses for their hypovirulence induction, biocontrol potential, and transmission properties between two vegetatively compatible but molecularly distinguishable fungal strains in live chestnut trees. The tested viruses, which are different in genome type (single-stranded or double-stranded RNA) and organization, replication site (cytosol or mitochondria), virus form (encapsidated or capsidless) and/or symptomatology, have been unexplored in the aforementioned aspects under controlled conditions. This study showed intriguing different in-tree behaviors of the seven viruses and suggested that to exert significant biocontrol effects, viruses must be able to induce hypovirulence and spread efficiently in the fungus infecting the chestnut trees.

Frozen in time: Rangewide genomic diversity, structure, and demographic history of relict American chestnut populations.

American chestnut (Castanea dentata) was once the most economically and ecologically important hardwood species in the eastern United States. In the first half of the 20th century, an exotic fungal pathogen-Cryphonectria parasitica-decimated the species, killing billions of chestnut trees. Two approaches to developing blight-resistant American chestnut populations show promise, but both will require introduction of adaptive genomic diversity from wild germplasm to produce diverse, locally adapted restoration populations. Here we characterize population structure, demographic history, and genomic diversity in a range-wide sample of 384 wild American chestnuts to inform conservation and breeding with blight-resistant varieties. Population structure analyses suggest that the chestnut range can be roughly divided into northeast, central, and southwest populations. Within-population genomic diversity estimates revealed a clinal pattern with the highest diversity in the southwest, which likely reflects bottleneck events associated with Quaternary glaciation. Finally, we identified genomic regions under positive selection within each population, which suggests that defence against fungal pathogens is a common target of selection across all populations. Taken together, these results show that American chestnut underwent a postglacial expansion from the southern portion of its range leading to three extant genetic populations. These populations will serve as management units for breeding adaptive genetic variation into the blight-resistant tree populations for targeted reintroduction efforts.

Temporal changes in pathogen diversity in a perennial plant-pathogen-hyperparasite system.

Hyperparasites can affect the evolution of pathosystems by influencing the stability of both pathogen and host populations. However, how pathogens of perennial hosts evolve in the presence of a hyperparasite has rarely been studied. Here, we investigated temporal changes in genetic diversity of the invasive chestnut blight pathogen Cryphonectria parasitica in the presence of its parasitic mycovirus Cryphonectria hypovirus 1 (CHV1). The virus reduces fungal virulence and represents an effective natural biocontrol agent against chestnut blight in Europe. We analysed genome-wide diversity and CHV1 prevalence in C. parasitica populations in southern Switzerland that were sampled twice at an interval of about 30 years. Overall, we found that both pathogen population structure and CHV1 prevalence were retained over time. The results suggest that recent bottlenecks have influenced the structure of C. parasitica populations in southern Switzerland. Strong balancing selection signals were found at a single vegetative incompatibility (vic) locus, consistent with negative frequency-dependent selection imposed by the vegetative incompatibility system. High levels of mating among related individuals (i.e., inbreeding) and genetic drift are probably at the origin of imbalanced allele ratios at vic loci and subsequently low vc type diversity. Virus infection rates were stable at ~30% over the study period and we found no significant impact of the virus on fungal population diversity. Consequently, the efficacy of CHV1-mediated biocontrol was probably retained.

Metabolites derived from fungi and bacteria suppress in vitro growth of Gnomoniopsis smithogilvyi, a major threat to the global chestnut industry.

INTRODUCTION: Chestnut rot caused by the fungus Gnomoniopsis smithogilvyi is a disease present in the world's major chestnut growing regions. The disease is considered a significant threat to the global production of nuts from the sweet chestnut (Castanea sativa). Conventional fungicides provide some control, but little is known about the potential of biological control agents (BCAs) as alternatives to manage the disease. OBJECTIVE: Evaluate whether formulated BCAs and their secreted metabolites inhibit the in vitro growth of G. smithogilvyi. METHODS: The antifungal potential of BCAs was assessed against the pathogen through an inverted plate assay for volatile compounds (VOCs), a diffusion assay for non-volatile compounds (nVOCs) and in dual culture. Methanolic extracts of nVOCs from the solid medium were further evaluated for their effect on conidia germination and were screened through an LC-MS-based approach for antifungal metabolites. RESULTS: Isolates of Trichoderma spp., derived from the BCAs, significantly suppressed the pathogen through the production of VOCs and nVOCs. The BCA from which Bacillus subtilis was isolated was more effective in growth inhibition through the production of nVOCs. The LC-MS based metabolomics on the nVOCs derived from the BCAs showed the presence of several antifungal compounds. CONCLUSION: The results show that G. smithogilvyi can be effectively controlled by the BCAs tested and that their use may provide a more ecological alternative for managing chestnut rot. The in vitro analysis should now be expanded to the field to assess the effectiveness of these alternatives for chestnut rot management.

Sweet tea (Lithocarpus polystachyus rehd.) as a new natural source of bioactive dihydrochalcones with multiple health benefits.

Sweet tea (Lithocarpus polystachyus Rehd.) has been consumed as herbal tea to prevent and manage diabetes for a long time. Recent studies indicate that sweet tea is rich in a variety of bioactive compounds, especially a class of nonclassical flavonoids, dihydrochalcones. In order to provide a better understanding of sweet tea and its main dihydrochalcones on human health, this review mainly summarizes related literature in the recent ten years, with the potential molecular mechanisms emphatically discussed. Phlorizin, phloretin, and trilobatin, three natural sweeteners, are the main dihydrochalcones in sweet tea. In addition, sweet tea and its dihydrochalcones exhibit plenty of health benefits, such as antioxidant, anti-inflammatory, antimicrobial, cardioprotective, hepatoprotective, antidiabetic, and anticancer effects, which are associated with the regulation of different molecular targets and signaling pathways. Therefore, sweet tea, as a rare natural source of dihydrochalcones, can be processed and developed into nutraceuticals or functional foods, with the potential application in the prevention and management of certain chronic diseases.

Buckeye Rot of Tomato in India: Present Status, Challenges, and Future Research Perspectives.

Tomato in India is commonly exposed to various diseases of fungal, bacterial, and viral origin, resulting in substantial yield losses (≥50%). Buckeye rot (caused by Phytophthora nicotianae var. parasitica) is among the major constraints in the successful cultivation of tomato crops in various parts of the world, including the Solan district of Himachal Pradesh state, India. The fruit rot becomes more devastating under high humidity and wet soils. Symptoms generally appear on green fruit as alternate dark- and light-brown concentric rings. The genome size of P. nicotianae var. parasitica is 82 Mb with >23,000 predicted genes. High humidity (>60%) and optimal temperatures (20 to 25°C), along with rainfall (≥10 mm), help to disperse the pathogen because the inoculum reaches the fruit through splashing rain. Sporangia germinate indirectly by producing zoospores at 20 to 25°C or directly via germ tubes at >25°C. In the absence of suitable resistant varieties, no single management practice is sufficient to keep the disease below the economic threshold level; therefore, integration of cultural and chemical methods is preferable. This article aims to focus on the etiology and management challenges of buckeye rot. We recommend innovative disease management strategies such as identification and deployment of resistant cultivars as well as spraying of synthetic chemical fungicides, biocontrol agents, and use of abiotic chemicals that induce resistance for developing sustainable crop production practices.

Transcriptome Analysis Reveals the Regulatory Networks of Cytokinin in Promoting Floral Feminization in Castanea henryi.

Castanea henryi is a monoecious plant with a low female-to-male ratio, which limits its yield. The phytohormone cytokinin (CK) plays a crucial role in flower development, especially gynoecium development. Here, the feminizing effect of CK on the development of C. henryi was confirmed by the exogenous spraying of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU). Spraying CPPU at 125 mg·L-1 thrice changed the male catkin into a pure female catkin, whereas at 5 mg·L-1 and 25 mg·L-1, only a part of the male catkin was transformed into a female catkin. A comparative transcriptome analysis of male catkins subjected to CPPU was performed to study the mechanism of the role of CKs in sex differentiation. Using Pearson's correlation analysis between hormone content and hormone synthesis gene expression, four key genes, LOG1, LOG3, LOG7 and KO, were identified in the CK and GA synthesis pathways. Moreover, a hub gene in the crosstalk between JA and the other hormone signaling pathways, MYC2, was identified, and 15 flowering-related genes were significantly differentially expressed after CPPU treatment. These results suggest that CK interacts with other phytohormones to determine the sex of C. henryi, and CK may directly target floral organ recognition genes to control flower sex.