This study aimed to reuse groundnut oil processing by-product, groundnut cake (GNC) for the low-cost production of prodigiosin (PG) via microbial technology and to assess its novel potential application for the management of black pepper nematodes. Serratia marcescens TUN02 was found as the most active PG-producing strain. Various small-scale experiments conducted in flasks indicated that GNC at 1% may be used as the sole carbon/nitrogen source for cost-effective PG production by fermentation. Notably, no further commercial ingredients and salts are required to supplement into the culture medium of this fermentation. PG was further investigated for scale-up production in a 14-L bioreactor system and PG was produced at high yield (6886 mg/L) with large-scale volume (4 L) in a short cultivation time (10 h). PG was then purified and its nematicidal activity was evaluated and showed effective inhibition of juveniles and egg hatching of Meloidogyne incognita species, harmful on black pepper, with low IC50 values of 0.2 and 0.32 mg/mL, respectively. The simple medium containing 1% GNC is the first report of cost-effective biosynthesis of PG, as well as potential in vitro anti-egg hatching activity of PG. These results indicated the potential application of GNC for low-cost bioproduction of PG for promising and novel use in the management of black pepper nematodes.
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.
Robusta coffee is a major commercial crop in the Central Highland of Vietnam with high economic and export value. However, this crop is adversely affected by various pathogens, particularly nematodes. This study aimed to screen active anti-nematode rhizobacterial strains for sustainable coffee production. Among more than 200 isolates, the isolate TUN03 demonstrated efficient biocontrol with nearly 100% mortality of J2 coffee nematodes Meloidogyne spp. and 84% inhibition of nematode egg hatching. This active strain was identified as Pseudomonas aeruginosa TUN03 based on its 16S rRNA gene sequence and phylogenetic analysis. In greenhouse tests, the strain TUN03 significantly reduced the coffee nematode population in the rhizome-soil with an 83.23% inhibition rate and showed plant growth-promoting effects. Notably, this is the first report of the nematicidal effect of P. aeruginosa against coffee nematodes. This potent strain further showed an antifungal effect against various crop-pathogenic fungi and was found to be the most effective against Fusarium solani F04 (isolated from coffee roots) with a 70.51% inhibition rate. In addition, high-performance liquid chromatography analysis revealed that this bacterial strain also secretes plant growth regulators including indole acetic acid (IAA), gibberellic acid (GA3), kinetin, and zeatin in significant amounts of 100, 2700, 37, and 9.5 µg/mL, respectively. The data from this study suggest that P. aeruginosa TUN03 may be a potential biocontrol agent and biofertilizer for the sustainable production of Robusta coffee and other crops.
Background
Nano-particles of metals can be routinely synthesized. The cereal seeds treatment with the particles can improve early growth and crop production. Moreover, the treatment is robust and economical.
Methods
Metal (Fe0, Cu0, Co0), zinc oxide (ZnO) and chitosan-stabilized silver nano-particles were synthesized and applied to cereal seeds. The germination rate, early plant development and inhibition effects on pathogenic fungi were quantified.
Results
It was found that all nano-particles had a positive effect on the development of healthy cereal seedlings. In particular, the length of the above-ground part of the seedlings was increased by 8–22%. The highest inhibition effect was observed on Helminthosporium teres with the application of Co0 and chitosan-Ag. Pre-sowing treatment with metal nano-particles reduced the number of infected grains by two times for wheat and 3.6 times for barley. The application also increases the chlorophylls and carotenoids in both uninfected and infected seedlings.
Conclusions
The results demonstrated a robust application of nano-particles in improving cereal production.
Graphical Abstract
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