Potato common scab is an important soilborne disease worldwide that can significantly reduce the quality and economic values of potato. The disease is caused by multiple species of Streptomyces, which are not well controlled due to lack of effective strategies. Streptomyces galilaeus has been recently identified as a dominant species causing potato common scab in Inner Mongolia, China. This study was focused on screening and characterizing antagonists for biological control against pathogenic S. galilaeus. Bacterial strain PBSH9 was isolated from a potato tuber. PBSH9 was identified as a Streptomyces sp. on the basis of morphological, physiological, and biochemical characteristics, as well as DNA sequence analysis. PBSH9 inhibited S. galilaeus with a diameter of inhibitory zone of 19.8 mm on agar plates. The extracellular filtrate of PBSH9 also inhibited S. galilaeus growth with a diameter of inhibition zone of 10.0 mm. Furthermore, PBSH9 promoted potato sprouting and emergence. Disease control was up to 81.88% in greenhouse trials, and from 47.64 to 73.97% in 3-year field trials. Among the tested inoculation methods, seed treatment was more effective than soil drenching for PBSH9 application. PBSH9 not only effectively controlled potato common scab but also increased potato growth. Thus, it can be a potential candidate for biocontrol agent.

Stem canker and black scurf of potatoes, caused by Rhizoctonia solani, are economically important diseases. Although the field application of sodium silicate has been shown to improve potato’s resistance against R. solani, the underlying mechanism remains unclear. In this study, we examined this resistance using transcriptomic analysis. Potato stems inoculated with R. solani were treated with sodium silicate, while a control group received no sodium silicate treatment. The plants were grown under natural environmental conditions at the farm of Inner Mongolia Agricultural University. Potato stems were sampled 4, 8, and 12 days after treatment. Total RNA was extracted using the TRIzol reagent and transformed into cDNA. The cDNA was sequenced, the reads were aligned, and the expression levels of genes were quantified and compared between the treated and control groups. A total of 1491 genes were identified as differentially expressed genes (DEGs). Furthermore, these DEGs were found to be involved in hydrolase activity, plant–pathogen interactions, hormone signal transduction, and the phenylpropanoid biosynthesis pathway. To confirm the up- and down-regulation of DEGs, quantitative real-time polymerase chain reaction (qRT-PCR) was performed on randomly selected genes. The results showed that the application of sodium silicate induces a complex defense network in potato plants involving physical barriers, innate immunity, phytohormone signaling, and various phenylpropanoid compounds to combat R. solani infection. This study provides valuable insights into the molecular mechanisms underlying sodium-silicate-induced resistance and its potential for reducing stem canker and black scurf in potato crops.

China is the largest strawberry producer in the world. Strawberry black root rot is a novel disease that occurs in Hohhot, Inner Mongolia. In the present study, the inhibitory effects of Bacillus subtilis S-16 and its fermented form on strawberry black root rot caused by Fusarium asiaticum were tested. The inhibition rates were 56.31% and 65.95%, respectively. Furthermore, the metabolic substances were analysed using LC-MS/MS. A total of 68 substances were identified, including 18 amino acids, 7 of which have been reported to have pro-growth and antibacterial functions. Among these seven amino acids, N-acetyl-D-alloisoleucine (NAD) had the strongest inhibitory effect on F. asiaticum. In addition, NAD caused the mycelia of F. asiaticum to appear shrivelled and deformed under electron microscopy. Furthermore, the effect of NAD on F. asiaticum was tested. The results indicate that NAD had a better prevention effect when used with hymexazol. Finally, the fungal biomass of F. asiaticum in strawberry roots was measured at different times using two treatment methods: treating plant roots with NAD and a spore suspension of F. asiaticum concurrently and with F. asiaticum alone. The colonisation response of F. asiaticum in terms of the target gene EF-1α when treated with F. asiaticum alone at 72 hpi was significantly higher than that when treated with NAD and a spore suspension of F. asiaticum. The relative expression levels of defence-related genes in strawberry roots treated with NAD at 72 hpi were determined. The genes NPR1 and PDF1 were markedly upregulated compared with other genes, suggesting that the expression of genes related to disease resistance was activated by NAD, resulting in disease resistance in strawberries. Our results provide theoretical support for the biological control of strawberry black root rot.

Potato common scab (PCS) is a soil-borne disease caused by Streptomyces spp. It is a serious problem and S. galilaeus is the predominant causal agent of PC

Background: Rhizoctonia solani causes stem canker and significantly impacts the production of potato. Conventional assay to evaluate potato resistance using R. solani inoculum is time consuming. To establish an effective and fast assay, 20 potato germplasms were examined using both R. solani inoculum and R. solani-derived toxin (RS toxin). Results: In field trials of 2009 and 2010, wheat-bran-based inoculum of R. solani was incorporated at either 0, 2, 3, 4 or 5 g per seed piece in the soil followed by sowing potato seed pieces in the furrow. Stem canker was evaluated in the growing season. Inoculum of wheat-bran-based 2, 3, or 4 g could well distinguish resistance of potato germplasms. For a quick assay of resistance screening, a toxin-based method was established by treating potato seedlings with the toxin of R. solani (RS toxin). RS toxin was prepared by heating R. solani culture. Potato seedlings were obtained through tissue culture and grown in Murashige and Skoog medium. Seedlings at the stage of 12 cm in height were transferred into agar medium amended with RS toxin and incubated for eight days. The inhibition caused by RS toxin was positively correlated with toxin concentration. By evaluating various potato cultivars that have different sensitivities to toxin, the inhibition of potato stems sections and seedlings was from 33% to 100% and from 32% to 148%, respectively. Results of toxin-based evaluation were highly correlated with the field data using pathogen inoculum (r = 0.731, P < 0.01). Conclusions: Inoculation with wheat bran-mediated R. solani of 2, 3 or 4 g per seed piece was an effective method for the evaluation of potato resistance in field trials. The toxin-based assay could improve efficiency and speed of disease resistance evaluation of potato germplasms. Both assays showed that none of the 20 potato materials was completely resistant to R. solani. However, cultivar ‘Desiree’ had the lowest level of disease, whereas ‘Atlantic’, ‘Favorita’, and ‘Shepody’ showed the high susceptibility.