Streptomyces virginiae XDS1-5, an antagonistic actinomycete, as a biocontrol to peach brown rot caused by Monilinia fructicola.

BACKGROUND: Peach brown rot, caused by the pathogen Monilinia fructicola, represents a significant postharvest infectious disease affecting peach fruit. This disease is responsible for a substantial increase in fruit decay rates, leading to significant economic losses, often exceeding 50%. Currently, there is a growing interest in identifying biocontrol agents to mitigate peach brown rot, with a predominant interest in Bacillus species. RESULTS: In this investigation, we isolated 410 isolates of actinomycetes from non-farmland ecosystem soil samples. Subsequently, 27 isolates exhibiting superior inhibitory capabilities were selected. Among these, strain XDS1-5 demonstrated the most robust fungistatic effect against brown rot disease, achieving an 80% inhibition rate in vitro and a 66% inhibition rate in vivo. XDS1-5 was identified as belonging to the Streptomyces virginiae species. Furthermore, a fermentation filtrate of XDS1-5 exhibited the ability to metabolize 34.21% of the tested carbon sources and 7.37% of the tested nitrogen sources. Particularly noteworthy was its capacity to disrupt the cell membrane structure directly, leading to increased cell membrane permeability and cytoplasmic leakage. Additionally, our investigation indicated that indoline, a metabolite produced by XDS1-5, played a pivotal role in inhibiting the growth of M. fructicola. CONCLUSION: In summary, our study has identified a biocontrol actinomycete, XDS1-5, with the potential to effectively inhibit postharvest brown rot disease in peaches. This finding holds great significance for the biological control of peach brown rot, offering promising prospects for mitigating the economic losses associated with this devastating disease. © 2024 Society of Chemical Industry.

Self-Healable and Recyclable Dual-Shape Memory Liquid Metal-Elastomer Composites.

Liquid metal (LM)-polymer composites that combine the thermal and electrical conductivity of LMs with the shape-morphing capability of polymers are attracting a great deal of attention in the fields of reconfigurable electronics and soft robotics. However, investigation of the synergetic effect between the shape-changing properties of LMs and polymer matrices is lacking. Herein, a self-healable and recyclable dual-shape memory composite, comprising an LM (gallium) and a Diels-Alder (DA) crosslinked crystalline polyurethane (PU) elastomer, is reported. The composite exhibits a bilayer structure and achieves excellent shape programming abilities, due to the phase transitions of the LM and the crystalline PU elastomers. To demonstrate these shape-morphing abilities, a heat-triggered soft gripper, which can grasp and release objects according to the environmental temperature, is designed and built. Similarly, combining the electrical conductivity and the dual-shape memory effect of the composite, a light-controlled reconfigurable switch for a circuit is produced. In addition, due to the reversible nature of DA bonds, the composite is self-healable and recyclable. Both the LM and PU elastomer are recyclable, demonstrating the extremely high recycling efficiency (up to 96.7%) of the LM, as well as similar mechanical properties between the reprocessed elastomers and the pristine ones.

Tough hybrid microgel-reinforced hydrogels dependent on the size and modulus of the microgels.

Microgel-reinforced (MR) hydrogels are tough hydrogels with dispersed rigid microgels embedded in a continuous soft matrix. MR gels have the great potential to provide not only mechanical toughness but also the desired functional matrix by incorporation of various functional microgels. Understanding the toughening mechanism of the MR hydrogels is critical for the rational design of the desired functionally tough MR gels. However, our current knowledge of the toughening mechanism of MR gels mainly comes from the MR hydrogels with both chemically crosslinked dispersed microgels and a continuous matrix. Little is known about the hybrid MR gels with physically crosslinked microgels embedded in a chemically crosslinked matrix. Herein, we synthesize such hybrid MR hydrogels with the ionic crosslinked calcium alginate microgels incorporated into the chemically crosslinked polyacrylamide (PAAm) matrix. The alginate microgels show strong size and modulus effects on the toughening enhancement: the larger microgels could toughen the MR gels more than the small ones, and the microgels with medium modulus could maximize the toughness of the MR gels. By comparison of the mechanical performances of the MR and the corresponding double network (DN) hydrogels, we have proposed that the hybrid MR gels may have the same toughening mechanism as the bulk DN gel. This work tries to better understand the structure-property relationships of both MR and DN gels and help in the design of more functionally tough MR gels with the desired properties.

Understanding the Resistance Mechanism in Brassica napus to Clubroot Caused by Plasmodiophora brassicae.

Exploring the mechanism of plant resistance has become the basis for selection of resistance varieties but reports on revealing resistant mechanism in Brassica napus against Plasmodiophora brassicae are rare. In this study, RNA-seq was conducted in the clubroot-resistant B. napus breeding line ZHE-226 and in the clubroot-susceptible rapeseed cultivar Zhongshuang 11 at 0, 3, 6, 9, and 12 days after inoculation. Strong alteration was detected specifically in ZHE-226 as soon as the root hair infection happened, and significant promotion was found in ZHE-226 on cell division or cell cycle, DNA repair and synthesis, protein synthesis, signaling, antioxidation, and secondary metabolites. Combining results from physiological, biochemical, and histochemical assays, our study highlights an effective signaling in ZHE-226 in response to P. brassicae. This response consists of a fast initiation of receptor kinases by P. brassicae; the possible activation of host intercellular G proteins which might, together with an enhanced Ca2+ signaling, promote the production of reactive oxygen species; and programmed cell death in the host. Meanwhile, a strong ability to maintain homeostasis of auxin and cytokinin in ZHE-226 might effectively limit the formation of clubs on host roots. Our study provides initial insights into resistance mechanism in rapeseed to P. brassicae.

The Major Fusarium Species Causing Maize Ear and Kernel Rot and Their Toxigenicity in Chongqing, China.

Fusarium verticillioides, F. proliferatum, and F. meridionale were identified as the predominant fungi among 116 Fusarium isolates causing maize ear and kernel rot, a destructive disease in Chongqing areas, China. The toxigenic capability and genotype were determined by molecular amplification and toxin assay. The results showed that the key toxigenic gene FUM1 was detected in 47 F. verticillioides and 19 F. proliferatum isolates. Among these, F. verticillioides and F. proliferatum isolates mainly produced fumonisin B1, ranging from 3.17 to 1566.44, and 97.74 to 11,100.99 µg/g for each gram of dry hyphal weight, with the averages of 263.94 and 3632.88 µg/g, respectively, indicating the F. proliferatum isolates on average produced about an order of magnitude more fumonisins than F. verticillioides did in these areas, in vitro. Only NIV genotype was detected among 16 F. meridionale and three F. asiaticum isolates. Among these, 11 F. meridionale isolates produced NIV, varying from 17.40 to 2597.34 µg/g. ZEA and DON toxins were detected in 11 and 4 F. meridionale isolates, with the toxin production range of 8.35-78.57 and 3.38-33.41 µg/g, respectively. Three F. asiaticum isolates produced almost no mycotoxins, except that one isolate produced a small amount of DON. The findings provide us with insight into the risk of the main pathogenic Fusarium species and a guide for resistance breeding in these areas.

Identification and Characterization of Three Monilinia Species from Plum in China.

In total, 112 Monilinia spp. single-spore isolates were collected from plum fruit (Prunus salicina) symptomatic for brown rot disease from Yunnan, Hubei, and Zhejiang provinces and Chongqing municipality, China between 2012 and 2014. Three distinct colony morphologies (phenotypes) were observed on potato dextrose agar and two isolates per phenotype were selected for further analysis. Colony color, colony shape, conidia size, number of germ tubes per conidia, and pathogenicity on plum were investigated. The ribosomal internal transcribed spacer regions 1 and 2 as well as a polymerase chain reaction-based method that amplified fragments of the glyceraldehyde-3-phosphate dehydrogenase (G3PDH) and ß-tubulin (TUB2) genes were used to identify the isolates to the species level. The three phenotypes were identified to be three different species: Monilinia fructicola, Monilia mumecola, and Monilia yunnanensis. Phylogenetic analysis based on G3PDH and TUB2 nucleotide sequences revealed that isolates within species clustered together regardless of host or geographical origin, suggesting that these factors did not play an important role for the evolutionary separation of the described species.