Isolation, Plant Growth-Promoting Properties, and Whole-Genome Sequence of a Novel Paenibacillus Species.

This work aimed to isolate and characterize a novel chitin-degrading bacterium from Yok Don National Park, Vietnam, for crop production studies. Among the chitinolytic isolates, strain YSY-4.3 was selected, which grew rapidly and produced a large halo around the colony. 16S rDNA analysis indicated that the strain is a novel species in the genus paenibacillus, and an in vitro evaluation showed that the strain produced phytohormones (IAA, GA3, and zeatin), biofilms, and siderophores; possessed cellulase; and exerted antifungal activity. The whole genome of the strain was 5,628,400 bp with 49.3% GC content, 5056 coding sequences, 48 tRNA, and 1 rRNA. It shared the highest values of digital DNA-DNA hybridization (67.4%) and average nucleotide identity (89.54%) with those of Paenibacillus woosongensis B2_4 (CP126084.1), suggesting a novel species. Of the coding sequences, 4287 proteins were identified by COG, and 2561 were assigned by KEGG. The genome contained at least 51 genes involved in plant growth and resistance to heavy-metal toxicity and 359 carbohydrate-active enzymes. The chitinolytic system of the strain was composed of 15 enzymes, among them, PsChiC, which contained a GH18 catalytic domain and a GH5 catalytic domain, had not been previously reported. In addition, the genome possessed 15 gene clusters encoding antimicrobial metabolites, 10 of which are possible novel clusters. This study expands knowledge regarding novel chitinolytic bacteria from Yok Don National Park and provides a valuable gene resource for future studies.

Novel resources of chitinolytic bacteria isolated from Yok Don National Park, Vietnam.

AIMS: This study focused on the isolation and characterization of chitinolytic bacteria from Yok Don National Park, Vietnam for future studies regarding biofertilizers and biocontrol agents. METHODS AND RESULTS: Chitinolytic bacteria were isolated from soils and chitin flakes soaked in river water at the National Park. On the basis of the halo zones caused by colloidal chitin degradation and colony morphologies, 12 chitinolytic strains were chosen from 15 700 isolates for various examinations. Findings from 16S rDNA analysis indicated that among these strains, 10 could be identified as different species, and the remaining 2 showed less identity to known species and genera. The 12 bacteria possess numerous properties concerning plant growth promotion and/or phytopathogenic biocontrol. Paenibacillus chitinolyticus YSY-3.1, which exhibited the highest chitinase activity and remarkable properties for plant growth, was chosen for sequencing and draft genome analysis. The results showed that the genome is 6571 781 bp in length with 6194 coding sequences, 52.2% G + C, and 96.53% ANI value. It harbors the chitinolytic system comprising 22 enzymes. Among these enzymes, PcChiQ has a loop structure different from that of known family 19 chitinases, PcChiA contains two GH18 catalytic domains rarely found in microorganisms, and PcChiF contains three GH18 catalytic domains that have never been reported. CONCLUSIONS: The 12 identified chitinolytic bacteria exhibit great potential for further studies on plant growth-promoting and/or biocontrol properties. Among these bacteria, two strains might be good candidates for next examinations concerning novel species and/or genera, and strain YSY-3.1 could possess a novel chitinolytic system.

Expression, purification, and basic properties of a novel domain structure possessing chitinase from Escherichia coli carrying the family 18 chitinase gene of Bacillus velezensis strain RB.IBE29.

BACKGROUND: Bacillus velezensis possesses numerous chitinolytic enzymes; however, not much is known about the role of its chitinase molecules. METHODS AND RESULTS: In this study, the chiA gene, which encodes a novel domain structure possessing family 18 chitinase from B. velezensis RB.IBE29, was expressed successfully in Escherichia coli BL21-CodonPlus (DE3)-RIPL using the pColdII expression vector. The recombinant protein, rBvChiA, was purified using the HisTrap FF column. Purified rBvChiA showed hydrolytic activity against insoluble chitin and bound to chitinous substrates. In addition, the purified recombinant enzyme displayed remarkable inhibition effects on the spore germination of Fusarium falciforme and the egg hatch of root-knot nematodes (Meloidogyne spp.), which are the main causes of black pepper diseases in the Central Highlands region, Vietnam. CONCLUSION: The current work results might enable further studies to develop novel chitinase A and strain RB.IBE29 as a natural fungicide and nematicide for sustainable black pepper production and other crops in the Central Highlands, Vietnam. This is the second report describing chitinase from B. velezensis based on the experimental data.

Molecular analysis of genes involved in chitin degradation from the chitinolytic bacterium Bacillus velezensis.

Bacillus velezensis RB.IBE29 is a potent biocontrol agent with high chitinase activity isolated from the rhizosphere of black pepper cultivated in the Central Highlands, Vietnam. Genome sequences revealed that this species possesses some GH18 chitinases and AA10 protein(s); however, these enzymes have not been experimentally characterized. In this work, three genes were identified from the genomic DNA of this bacterium and cloned in Escherichia coli. Sequence analysis exhibited that the ORF of chiA consists of 1,203 bp and encodes deduced 45.46 kDa-chitinase A of 400 aa. The domain structure of chitinase A is composed of a CBM 50 domain at the N-terminus and a catalytic domain at the C-terminus. The ORF of chiB includes 1,263 bp and encodes deduced 47.59 kDa-chitinase B of 420 aa. Chitinase B consists of two CBM50 domains at the N-terminus and a catalytic domain at the C-terminus. The ORF of lpmo10 is 621 bp and encodes a deduced 22.44 kDa-AA10 protein, BvLPMO10 of 206 aa. BvLPMO10 contains a signal peptide and an AA10 catalytic domain. Chitinases A and B were grouped into subfamily A of family 18 chitinases. Amino acid sequences in their catalytic domains lack aromatic residues (Trp, Phe, Tyr) probably involved in processivity and substrate binding compared with well-known bacterial GH18 chitinases. chiB was successfully expressed in E. coli. Purified rBvChiB degraded insoluble chitin and was responsible for inhibition of fungal spore-germination and egg hatching of plant-parasitic nematode. This is the first report describing the analysis of the chitinase system from B. velezensis.

Chitinase system of Aeromonas salmonicida, and characterization of enzymes involved in chitin degradation.

The genes encoding chitin-degrading enzymes in Aeromonas salmonicida SWSY-1.411 were identified and cloned in Escherichia coli. The strain contained two glycoside hydrolase (GH) families 18 chitinases: AsChiA and AsChiB, two GH19 chitinases: AsChiC and AsChiD, and an auxiliary activities family 10 protein, lytic polysaccharide monooxygenase: AsLPMO10A. These enzymes were successfully expressed in E. coli and purified. AsChiB had the highest hydrolytic activity against insoluble chitin. AsChiD had the highest activity against water-soluble chitin. The peroxygenase activity of AsLPMO10A was lower compared to SmLPMO10A from Serratia marcescens. Synergism on powdered chitin degradation was observed when AsChiA and AsLPMO10A were combined with other chitinases of this strain. More than twice the increase of the synergistic effect was observed when powdered chitin was treated by a combination of AsLPMO10A with all chitinases. GH19 chitinases suppressed the hyphal growth of Trichoderma reesei.

Gene deletion of Corynespora cassiicola cassiicolin Cas1 suppresses virulence in the rubber tree.

Corynespora cassiicola is an ascomycete fungus causing important damages in a wide range of plant hosts, including rubber tree. The small secreted protein cassiicolin is suspected to play a role in the onset of the disease in rubber tree, based on toxicity and gene expression profiles. However, its exact contribution to virulence, compared to other putative effectors, remains unclear. We created a deletion mutant targeting the cassiicolin gene Cas1 from the highly aggressive isolate CCP. Wild-type CCP and mutant ccpΔcas1 did not differ in terms of mycelium growth, sporulation, and germination rate in vitro. Cas1 gene deletion induced a complete loss of virulence on the susceptible clones PB260 and IRCA631, as revealed by inoculation experiments on intact (non-detached) leaves. However, residual symptoms persisted when inoculations were conducted on detached leaves, notably with longer incubation times. Complementation with exogenous cassiicolin restored the mutant capacity to colonize the leaf tissues. We also compared the toxicity of CCP and ccpΔcas1 culture filtrates, through electrolyte leakage measurements on abraded detached leaves, over a range of clones as well as an F1 population derived from the cross between the clones PB260 (susceptible) and RRIM600 (tolerant). On average, filtrate toxicity was lower but not fully suppressed in ccpΔcas1 compared to CCP, with clone-dependent variations. The two QTL, previously found associated with sensitivity to CPP filtrate or to the purified cassiicolin, were no longer detected with the mutant filtrate, while new QTL were revealed. Our results demonstrate that: (1) cassiicolin is a necrotrophic effector conferring virulence to the CCP isolate in susceptible rubber clones and (2) other effectors produced by CCP contribute to residual filtrate toxicity and virulence in senescing/wounded tissues. These other effectors may be involved in saprotrophy rather than necrotrophy.

Identification and characterization of chitinolytic bacteria isolated from a freshwater lake.

To develop a novel type of biocontrol agent, we focus on bacteria that are characterized by both chitinase activity and biofilm development. Chitinolytic bacteria were isolated from sediments and chitin flakes immersed in the water of a sand dune lake, Sakata, in Niigata, Japan. Thirty-one isolates from more than 5100 isolated strains were examined chitinase activity and biofilm formation. Phylogenetic analysis of these isolates based on the 16S rRNA gene sequences revealed that most isolates belonged to the family Aeromonadaceae, followed by Paenibacillaceae, Enterobacteriaceae, and Neisseriaceae. The specific activity of chitinase of four selected strains was higher than that of a reference strain. The molecular size of one chitinase produced by Andreprevotia was greater than that of typical bacterial chitinases. The dialyzed culture supernatant containing chitinases of the four strains suppressed hyphal growth of Trichoderma reesei. These results indicate that these four strains are good candidates for biocontrol agents.

Endophytic bacterial dataset of the Cavendish banana grown in Dak Lak Province of Vietnam using 16S rRNA gene metabarcoding.

The Cavendish banana (Musa cavendishii L.) is one of the main perennial crops grown in Dak Lak Province of Vietnam. However, data on the endophytic bacterial community of this plant are unknown. In this work, a representative sample, mixing from 5 root samples collected from five banana gardens (the Dwarf Cavendish cultivar) in Dak Lak, was used for analyzing the endophytic microbiome using 16S rRNA gene metabarcoding. Results showed that 5 phyla, 7 classes, 20 orders, 31 families, and 47 genera of endophytic bacteria were identified from the sample. Bacteria belonging to phylum Proteobacteria were the most predominant, with 72.64%, and functions involved in biosynthesis were the most abundant, with 75.35%, of the endophytic bacterial community. Data help to understand the endophytic bacterial community of the Cavendish banana cultivated in Dak Lak, Vietnam. These data can be useful for further experiments concerning relationships between the growth of the Cavendish banana and endophytic bacteria. This is the first report on the endophytic bacteria of the Cavendish banana cultivated in Dak Lak, Vietnam.

16S rRNA metagenomic dataset on endophytic bacterial community of the cashew plant (Anacardium occidentale L.) grown in Dak Lak Province of Vietnam.

Vietnam is currently one of the largest producers and exporters of cashew nuts in the world. Cashew (Anacardium occidentale L.) is one of the main industrial crops cultivated in Dak Lak Province of Vietnam. Comprehending the endophytic bacteria of this plant, a new biofertilizer for sustainable cashew nut production can be progressed. In this report, the cashew root sample was collected from cashew fields in 2021 in Dak Lak. The DNeasy Powersoil kit was used to extract the genomic DNA of endophytic bacteria from the root sample. The 16S rRNA genes (V1-V9 regions) were amplified by PCR, and libraries of amplicons were prepared using the Swift amplicon 16S plus ITS panel kit. The Illumina MiSeq platform was applied to sequence amplicon libraries using 16S rRNA metagenomics. Taxonomic analyses showed that Gammaproteobacteria (38.77 %) and Alphaproteobacteria (37.76 %) were the predominant classes among the endophytic bacteria. Functional analyses revealed that biosynthesis (72.78 %) was the primary function of the endophytic bacterial community. Raw sequences (Fastq files) have been deposited in Mendeley Data [1]. The obtained data provide insight into the endophytic bacterial community of cashews cultivated in Dak Lak Province of Vietnam. The data are valuable for further developing a new biofertilizer for cashew nut production using endophytic bacteria. Ours is the first report about endophytic bacterial communities of cashews cultivated in this province as well as the Central Highlands of Vietnam.

Whole genome sequence data of Paenibacillus tyrfis YSS-72.2.G2, a chitinolytic bacterium newly isolated from a National Park of Vietnam.

Paenibacillus tyrfis YSS-72.2.G2 is a soil chitinolytic bacterium newly isolated from Yok Don National Park of Vietnam. Our previous results demonstrated that this bacterium was a strong chitinase producer, possessed plant growth promotion, and had high activity against phytopathogenic fungi. However, the genome sequence of this strain is unknown. This work aimed to establish data on the genome sequence of P. tyrfis YSS-72.2.G2 and its chitinase system for further assessments regarding biocontrol mechanisms and plant growth promotion. The P. tyrfis YSS-72.2.G2 genome is 7,756,121 bp in size and 53.4 % G+C. It harbors 6,948 protein-coding genes, 5 rRNA genes, 82 tRNA genes, 4 ncRNA genes, 99 pseudo genes, and 5 CRISPR arrays. Genes involved in heavy metal resistance (5 genes), iron acquisition (5 genes), and IAA biosynthesis (5 genes) were predicted in the genome. There were 234 carbohydrate-active enzymes found in this genome; among them, 13 enzymes possibly possess activity against phytopathogens. Chitin-degrading system of YSS-72.2.G2 contains 15 chitinolytic enzymes. In addition, 28 gene clusters coding for antimicrobial metabolites were identified, of these, 14 show no sequence similarities to the known clusters. The raw sequences were submitted to the Sequence Read Archive on the National Center for Biotechnology Information with accession number PRJNA946889. The genome sequence of P. tyrfis YSS-72.2.G2 has been deposited in the DDBJ/GenBank/EMBL database under accession number NZ_BSDJ00000000. Data provide insight into the genomic information of strain YSS-72.2.G2. This is the first work reporting data on the genome sequence of P. tyrfis isolated from Vietnam.

Data on gene cloning, expression, purification, and characterization of the glycoside hydrolase family 11 from Bacillus velezensis.

Bacillus velezensis RB.IBE29 is a chitinolytic bacterium originally isolated from the rhizospheric soil of black pepper grown in Vietnam. This bacterium is a strong biocontrol agent against plant pathogens and possesses a novel chitinase system. Genome sequences available in CAZy database revealed B. velezensis possesses one gene encoding xylanase belonging to glycoside hydrolase family 11; however, this enzyme has yet to be un-experimentally characterized. In this work, xyA gene was isolated from the genomic DNA of strain RB.IBE29 and cloned in Escherichia coli DH5α cells using the pUC19 vector. Sequencing analysis showed that the ORF of xyA contains 642 bp and encodes the deduced xylanase with 213 aa and 23.27 kDa. The domain structure of the enzyme has a signal peptide and a family 11 catalytic domain. xyA (without peptide sequence) was successfully expressed in E. coli BL21-CodonPlus (DE3)-RIPL cells using the pColdII vector and purified using the HisTrap FF column. Purified recombinant xylanase degraded xylan substrates, had the highest hydrolytic activity at 55°C in 20 mM sodium phosphate buffer (pH 6.0), and MgCl2, CoCl2, and MnCl2 enhanced the enzymatic activity. Nucleotide sequence of xyA was submitted to the DDBJ/GenBank/EMBL under accession number LC779040. This is the first data on the gene cloning, expression, purification, and characterization of the glycoside hydrolase family 11 from B. velezensis.

Root endophytic microbiome dataset of sugarcane (Saccharum officinarum L.) cultivated in the Central Highlands, Vietnam, established by the 16S rRNA metagenomics.

Sugarcane (Saccharum officinarum L.) is one of the main annual crops grown in the Central Highlands of Vietnam. By understanding the taxonomic and functional profiles of root endophytic microbiome, we can develop a new cultivation technique for the sustainable production of this plant. In this work, a representative sample was obtained by mixing the roots collected from five different sugarcane fields in Dak Lak Province, the Central Highlands, in 2021. The genomic DNA of the endophytic bacteria was extracted using the DNeasy Powersoil kit, and the V1-V9 regions of the 16S rRNA genes were amplified by PCR. Libraries of 16S rRNA gene amplicons were prepared using the Swift amplicon 16S plus ITS panel kit. Finally, the Illumina MiSeq platform was used to sequence the 16S rRNA gene amplicons library. The raw data of the endophytic microbiome were uploaded to the National Center for Biotechnology Information (NCBI) with Bioproject PRJNA923851 and can be retrieved at https://www.ncbi.nlm.nih.gov/Traces/study/?acc=%20PRJNA923851. The obtained data provide basic information on the root endophytic microbiome of sugarcane cultivated in the Central Highlands of Vietnam. The data can also be useful for further developing a new technique for sustainable sugarcane production based on indigenous microorganisms. This work is the first report on the endophytic microbiome of sugarcane cultivated in this region.

Rice (Oryza sativa L.) cultivated in the Central Highlands of Vietnam: Dataset on the endophytic microbiome.

Rice (Oryza sativa L.) is the main annual crop cultivated in the Central Highlands region of Vietnam. Understanding the endophytic bacterial community of this plant, a new technique for sustainable production can be developed. In this work, a representative sample was obtained by combining rice (RVT variety) root samples collected from five different fields in Dray Sap Commune, Krong Ana District, Dak Lak Province, the Central Highlands of Vietnam. Using the Illumina MiSeq technology, the 16S rRNA metagenomics was applied to the sequencing amplicons library. The QIIME2 matched with the SILVA SSURef reference database was employed to analyze the taxonomic profile, and the PICRUSt2 and MetaCyc databases were used to predict the functional profile of rice endophytic prokaryotes. Results revealed that Enterobacterales was the most predominant class (57.7%) in the bacterial community, and biosynthesis was the primary function of the rice endophytic microbiome (75.95%). Raw sequences obtained in this work are available from the National Center for Biotechnology Information (NCBI) (Bioproject ID: PRJNA994482) and Mendeley Data [1]. Data in this work provide insight into the endophytic microbiome of rice (RVT variety) cultivated in the Central Highlands of Vietnam. These data are valuable for developing a new method for producing locally sustainable rice employing endophytic bacteria. This is the first report on the endophytic microbiome of rice cultivated in this region.

Complete genome sequence data of chitin-degrading Bacillus velezensis RB.IBE29.

This work reports the complete genome sequence of chitinolytic Bacillus velezensis RB.IBE29 recently isolated from the rhizosphere of black pepper cultivated in the Central Highlands region of Vietnam. This bacterium had strong antagonistic activity against phytopathogens and possessed a novel chitinase system. The complete genome of strain RB.IBE29 was sequenced using the platforms of Illumina (2×150 PE) and Oxford Nanopore technologies. Assembly showed that strain RB.IBE29 has one 3,957,092-bp circular chromosome with 46.5 % G+C content. DFAST analysis revealed the genome contains 3819 protein-coding genes, 27 rRNAs, 86 tRNAs, 1 tmRNA, 144 pseudogenes, and shares an ANI value of 97.51 % with that of reported B. velezensis NRRL B-41580. The B. velezensis RB.IBE29 genome possesses at least 42 genes concerning heavy metal resistance and plant-growth promotion. CAZymes analysis showed that 103 genes coding for carbohydrate-active enzymes were predicted in the genome, including 41 genes for glycoside hydrolases, 34 genes for glycosyl transferases, 3 genes for polysaccharide lyases, 17 genes for carbohydrate esterases, 6 genes for auxiliary activities, and 2 genes for carbohydrate-binding modules. Of these deduced enzymes, at least 8 probably possess activities against phytopathogens, such as family 18 chitinases, family 16 glucanase, and family 46 chitosanase. AntiSMASH analysis exhibited that 15 biosynthetic gene clusters were found in the genome; among them, 5 show no sequence similarity to known bacterial clusters. The raw sequences in this work were deposited in Mendeley Data. The complete genome sequence of strain RB.IBE29 was submitted to the DDBJ/GenBank/EMBL under accession number AP028932. The obtained data provide insight into the biocontrol ability and plant-growth promotion of B. velezensis RB.IBE29. The data are valuable for further explorations concerning crop production and other fields using gene expression approaches.

Rhizosphere microbiome dataset of Robusta coffee (Coffea canephora L.) grown in the Central Highlands, Vietnam, based on 16S rRNA metagenomics analysis.

Vietnam is the second-largest coffee producer in the world after Brazil. Of the two main coffee production species, namely, Arabica and Robusta, Vietnam is the largest producer of Robusta worldwide [1]. Based on previous reports, the planted coffee area in Vietnam was 695.600 ha and its production was 1.76 million tons in 2020, in which the Central Highlands region accounts for approximately 73% of the planted area and production [2]. Hence, this region is known as the capital of coffee plantations and production in Vietnam. Previous studies have focused on the diversity of rhizospheric bacteria from this plant species cultivated in this region based on cultivation methods [3], [4], [5], [6], [7], [8]. However, no report has been found on the rhizospheric microbial diversity of this important plant in Vietnam. To our knowledge, a dataset of rhizospheric microbial communities of the coffee plant grown in the Central Highlands is still unclear. This report presents a dataset of the rhizosphere microbiome from a representative sample obtained by mixing five rhizospheric soil samples of Coffea canephora L. cultivated in the Central Highlands region using metagenomic next-generation sequencing. This dataset provides information on the rhizospheric microbial diversity of Robusta coffee, particularly its functionality. Therefore, cultivation techniques for sustainable Robusta coffee production in the region could be developed by applying indigenous rhizospheric microbial resources.

Taxonomic and functional profiles of Coffea canephora endophytic microbiome in the Central Highlands region, Vietnam, revealed by analysis of 16S rRNA metagenomics sequence data.

Vietnam is the largest producer of Robusta coffee (Coffea canephora L.) [1]. Among regions in Vietnam, the Central Highlands is the capital of the coffee plantation and production [2]. Previous works have established a dataset of rhizospheric microbial diversity and its functionality to develop sustainable Robusta coffee production techniques in this region [3], [4], [5], [6]; however, a dataset of the endophytic microbiome of this plant species has been found is still unknown. The work presented here is the first report on the microbial and functional diversity of the endophytic microbiome of Coffea canephora L. grown in the region. A representative root sample was obtained by mixing five different root samples collected from a 6-year-old Robusta coffee field in Dak Lak Province, the Central Highlands, on 30 October 2021. After that, 16S rRNA metagenomic next-generation sequencing was conducted on the sample using the Illumina MiSeq platform. The raw sequence of endophytic microbiome data in this work was uploaded in Fastq format on NCBI with Bioproject PRJNA821717 and can be accessed at https://www.ncbi.nlm.nih.gov/Traces/study/?acc=PRJNA821717. The dataset can be useful for understanding basic information about the prokaryotic ecology of this important plant in the Central Highlands, Vietnam. The data can also be valuable for developing cultivation techniques for sustainable Coffea canephora L. production by applying indigenous microbial resources.

Analysis of endophytic microbiome dataset from roots of black pepper (Piper nigrum L.) cultivated in the Central Highlands region, Vietnam using 16S rRNA gene metagenomic next-generation sequencing.

Vietnam is the most prominent black pepper producer and exporter in the world. In 2020, the cultivated area of black pepper in Vietnam was 132.000 hectares and its production was 270.000 tons, in which the Central Highlands region took about 70% of both the cultivated area and production [1]. Hence, this region is thought to be the capital of black pepper cultivation and production in Vietnam. Numerous researches have investigated biodiversity and collected various beneficial endophytic bacteria from this plant in this region; however, traditional methods only were used to isolate such bacteria [2], [3], [4], [5]. Therefore, these studies have a limitation to providing insight into the profiles of the endophytic microorganism dataset in the black pepper plant. Most recently, our work based on the 16S rRNA gene amplicon sequencing revealed an insight into profiles of microbial diversity and its functionality from the sample collected from a forest in this region; however, that work was just focused on soil microbiome dataset from the dry deciduous dipterocarp forest in Yok Don national park [6]. To our knowledge, a dataset of endophytic microbiome of black pepper plant cultivated in the Central Highlands remains unclear. This report presents a dataset of the endophytic microbiome from a representative sample combined from five different root samples of black pepper (Vinh Linh local variety) cultivated in the Central Highlands of Vietnam using 16S rRNA gene metagenomic next-generation sequencing. The dataset in this work can provide information on the endophytic microbial diversity and its functionality. It can also be useful for developing cultivation techniques by applying endophytic microbial genetic resources for sustainable black pepper production in the Central Highlands, Vietnam, towards the nutrient need in different stages of development and growth.

Soil microbiome dataset from Yok Don national park in the Central Highlands region of Vietnam.

The Central Highlands region contains most of the national parks in Vietnam with different ecosystems, including the national parks of Kon Ka Kinh, Chu Mon Ray, Chu Yang Sin, Yok Don, Bidoup-Nui Ba, and Ta Dung. Thus, this region is considered a center with the highest biodiversity in Vietnam [1]. Among the national parks, Yok Don is unique in its conservation of the dry deciduous dipterocarp forest. Furthermore, Yok Don is the second-largest park in Vietnam; it has the most different ecosystem compared with other national parks in this region [2]. Although some studies have investigated biodiversity preservation in the region, some other studies have only dealt with medicinal plants, lichens, and the rhizospheric bacteria of cultivated black pepper [1,[3], [4], [5]. To the best of our knowledge, no research on the microbial communities in Yok Don national park and in the Central Highlands has been reported. At present, global warming and a decrease in the forest area in the Central Highlands have led to the ongoing reduction in biodiversity and microbial resources. The current study reports the microbiome dataset from the soil sample collected in Yok Don national park. Metagenomic next-generation sequencing was used to characterize the microbial communities in the sample. The metagenome dataset generated provides information on microbial diversity and its functionality and can be useful for further studies on the conservation and use of microbial genetic resources in this region.

Metagenomic next-generation sequencing of the microbiome dataset from the surface water sample collected from Serepok River in Yok Don National Park, Vietnam.

The Central Highlands region is considered as the center with the highest biodiversity in Vietnam because it has the majority of national parks such as Yok Don, Chu Yang Sin, Bidoup-Nui Ba, Ta Dung, Chu Mon Ray, and Kon Ka Kinh and nature reserves such as Ngoc Linh, Kon Chu Rang, Ea So, Nam Ka, and Nam Nung with different ecosystems [1]. Of the national parks and nature reserves, Yok Don has the most different ecosystem. Yok Don is the second biggest national park, and it is the only national park that conserves dry deciduous dipterocarp forests in Vietnam [2]. Presently, the decrease in forest area and global warming have led to the continuous reduction in microbial resources in this region. Thus, a dataset of the soil microbiome in this region has been established to explore microbial resources for conservation and further application in sustainable agricultural production in this region [3]; however, to the best of our knowledge, a dataset of water microbiome remains unknown. This work presented a microbiome dataset from surface water samples collected from Serepok River in Yok Don National Park, Vietnam. Metagenomic next-generation sequencing was used to characterize microbial communities in the sample. The raw sequence in this work was uploaded in Fastq format on NCBI, which can be accessed at https://www.ncbi.nlm.nih.gov/Traces/study/?acc=PRJNA853090. This metagenome dataset can provide valuable information on surface water microbial communities and their functionality. It can also be used for further studies on the conservation and application of indigenous microbial resources for sustainable crop production in this region.

Genetic Determinism of Sensitivity to Corynespora cassiicola Exudates in Rubber Tree (Hevea brasiliensis).

An indirect phenotyping method was developed in order to estimate the susceptibility of rubber tree clonal varieties to Corynespora Leaf Fall (CLF) disease caused by the ascomycete Corynespora cassiicola. This method consists in quantifying the impact of fungal exudates on detached leaves by measuring the induced electrolyte leakage (EL%). The tested exudates were either crude culture filtrates from diverse C. cassiicola isolates or the purified cassiicolin (Cas1), a small secreted effector protein produced by the aggressive isolate CCP. The test was found to be quantitative, with the EL% response proportional to toxin concentration. For eight clones tested with two aggressive isolates, the EL% response to the filtrates positively correlated to the response induced by conidial inoculation. The toxicity test applied to 18 clones using 13 toxinic treatments evidenced an important variability among clones and treatments, with a significant additional clone x treatment interaction effect. A genetic linkage map was built using 306 microsatellite markers, from the F1 population of the PB260 x RRIM600 family. Phenotyping of the population for sensitivity to the purified Cas1 effector and to culture filtrates from seven C. cassiicola isolates revealed a polygenic determinism, with six QTL detected on five chromosomes and percentages of explained phenotypic variance varying from 11 to 17%. Two common QTL were identified for the CCP filtrate and the purified cassiicolin, suggesting that Cas1 may be the main effector of CCP filtrate toxicity. The CCP filtrate clearly contrasted with all other filtrates. The toxicity test based on Electrolyte Leakage Measurement offers the opportunity to assess the sensitivity of rubber genotypes to C. cassiicola exudates or purified effectors for genetic investigations and early selection, without risk of spreading the fungus in plantations. However, the power of this test for predicting field susceptibility of rubber clones to CLF will have to be further investigated.