Study on Interactions between the Major Apple Valsa Canker Pathogen Valsa mali and Its Biocontrol Agent Saccharothrix yanglingensis Hhs.015 Using RT-qPCR

Abstract

The mechanism of biocontrol agent Saccharothrix yanglingensis Hhs.015 action against Valsa mali, a major apple Valsa canker pathogen, was examined using a novel, sensitive (minimum detection limit 100 pg/μL) and reliably RT-qPCR technique. Prior to lesion formation, total concentration of V. mali in the bark showed a significant decrease (p<0.05) after 24 h of Hhs.015 treatment. This was more pronounced at 48 and 96 h post treatment. After lesion formation, levels of V. mali remained constant at the boundary between infected and uninfected bark tissues, although the relative expansion rate of the lesion was significantly reduced (p<0.05). Gene expression levels of endo-polygalacturonase, a marker for fungal pathogenicity, were sharply reduced while host induced resistance callose synthase levels increased significantly (p<0.05) at the boundary bark at 9 d after Hhs.015 treatment. The results showed that biocontrol agent Hhs.015 prevented infection of V. mali by inhibiting pathogen growth, down-regulating pathogenicity factor expression and inducing a high level of host resistance.

Diversity and Antimicrobial Potential of Cultivable Endophytic Actinobacteria Associated With the Medicinal Plant Thymus roseus

“…The inhibition ratio of T4SB028 against Alternaria solani, Valsa malicola, and Valsa mali was 67.06, 64.20, and 70.55%, respectively. This had accordance with the previous study (le Roes-Hill and Meyers, 2009;Fan et al, 2016;Law et al, 2017). This result demonstrated the potential of strains Streptomyces sp.…”

“…For instance, a total of 150 endophytic actinobacteria were isolated from three medicinal plant species (Annonaceae squamosa, Camptotheca acuminata, and Taxus chinen), and 72.4% of them showed inhibition against more than one indicator microorganism, including Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Candida albicans, and Aspergillus niger (Wu et al, 2009). In addition, endophytic actinobacteria were antagonistic against Pythium aphanidermatum and significantly promoted plant growth and reduced the crown and root rot of cucumber that was caused by the Pythium aphanidermatum in vitro condition (El-Tarabily et al, 2009).…”

Transcriptome analysis of Valsa mali reveals its response mechanism to the biocontrol actinomycete Saccharothrix yanglingensis Hhs.015

“…In vitro experiments have shown that Sy Hhs.015 sterile fermentation filtrate can inhibit the growth of mycelium and conidia germination of Vm , and abnormal mycelia and cytoplasmic extravasation can be observed. Field experiments has shown that the relative control efficiency of apple trees infected with Vm after Sy Hhs.015 treatment was 61.29%, which was equivalent to that of treatment with difenoconazole and tebuconazole [ 11 ]. Studies have shown that Sy Hhs.015 can produce heteroauxin, chitinase, proteinase and glucanase, and the active substances isoflavones and pentamycin have been extracted from its fermentation broth [ 11 ].…”

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“…Two Chitinase 1 genes (KUI66287.1, KUI69708.1) among the DEGs were significantly downregulated (log2FC = -2.21). Meanwhile, chitinase, proteinase and glucanase produced by Sy Hhs.015 also destroyed the cell wall structure of Vm (Fan et al, 2016). Combining these factors, it can be speculated that Sy Hhs.015 damaged the cell wall of Vm and cell wall formation and cell division were blocked, resulting in the inhibition of Vm growth.…”

“…In vitro experiments has shown that Sy Hhs.015 sterile fermentation filtrate can inhibit the growth of mycelium and conidia germination of Vm, and abnormal mycelia and cytoplasmic extravasation can be observed. Field experiments has shown that the relative control efficiency of apple trees infected with Vm after Sy Hhs.015 treatment was 61.29%, which was equivalent to that of treatment with difenoconazole and tebuconazole (Fan et al, 2016). Studies have shown that Sy Hhs.015 can produce heteroauxin, chitinase, proteinase and glucanase, and the active substances isoflavones and pentamycin have been extracted from its fermentation broth (Fan et al, 2016).…”