A highly virulent and polyvalent Streptomyces phage was isolated from a potato field near Albany, Western Australia. The efficacy of the isolated phage to disinfest seed potato tubers artificially inoculated with a common scab-causing streptomycete was evaluated. The phage suspension was prepared in a mini-bioreactor. Diseased potatoes were bathed in a phage suspension (1 × 109 plaque-forming units per mL) for 24 h. The suspension was constantly circulated within a novel 25 L phage bath by means of an air-sparging pipe driven from an air compressor. Phage-treated scab-affected seed potatoes planted into free-draining polystyrene boxes containing steam-pasteurized field soil produced tuber progeny with significantly (P < 0·05) reduced levels of surface lesions of scab (1·2%) compared with tubers harvested from nonphage-treated tubers (23%). The number of scab lesions was also significantly reduced (P < 0·05) by phage treatment of mother tubers. No significant differences were recorded in weight, size or number of harvested tubers from phage-treated or nontreated mother tubers. This is the first in vivo study that has used Streptomyces phage to significantly disinfest seed potatoes of Streptomyces scabies and thereby reduce contamination of soil from seed-tuber-borne inoculum and reduce infection of daughter tubers.

Novel in vivo use of a polyvalent Streptomyces phage to disinfest Streptomyces scabies-infected seed potatoes

The discovery of the ellagitannin geraniin was made exactly 40 years ago. It is a secondary metabolite found in plants and is categorised as a hydrolysable tannin under the huge family of polyphenolic compounds. At present, the occurrence of geraniin has been verified in at least 71 plant species, many of which are used in traditional medicine. Hence, like other polyphenols, geraniin has also received widespread interest as a research focus to unearth its beneficial biological effects and therapeutic values apart from understanding its chemical properties, biosynthesis and interaction with the body system. Indeed, it has been demonstrated that geraniin possesses antioxidant, antimicrobial, anticancer, cytoprotective, immune-modulatory, analgesic properties besides exerting promising therapeutic effects on hypertension, cardiovascular disease and metabolic dysregulation. The objective of this review is to summarise the current knowledge about the basic chemistry, natural sources, isolation techniques, biosynthesis, pharmacokinetics and pharmacodynamics of geraniin. With reference to this information, the clinical significance, obstacles and future perspectives in geraniin research will also be scrutinised.

Ellagitannin geraniin: a review of the natural sources, biosynthesis, pharmacokinetics and biological effects

The fungicidal activity of five methanolic plant extracts from Lantana camara, Salvadora persica, Thymus vulgaris, Zingiber officinale and Ziziphus spina-christi were evaluated for their antifungal efficiency on tomato phytopathogenic fungi, Fusarium oxysporum, Pythium aphanidermatum and Rhizoctonia solani, the causative agents of tomato damping-off diseases. Three of five plant extracts were effective against thees phytopathogenic fungi. T. vulgaris and Z. officinale extracts were strongly active and showed fungistatic and fungicidal activities against the phytopathogenic fungi with minimal inhibitory concentration (MIC of 4 mg ml-1 and minimal fungicidal concentrations (MFC) of 8 mg ml-1 except F. oxysporum which was less sensitive and its MFC reached to 16 mg ml-1 of Z. officinale extract. On the other hand, S. persica extract showed a moderate antifungal activity while L. camara and Z. spina-christi were not effective against tomato phytopathogenic fungi except P. aphanidermatum which was completely inhibited at 10 mg ml-1 of L. camara extract. Carbendazim fungicide was more effective than all methanolic plant extracts inhibiting mycelial growth of all phytopathogenic fungi at 8 ppm and a huge concentration reached to 8 mg ml-1 of the effective plant extract was required to attain the same effect. Analysis of the effective plant extracts by GC/MS revealed that T. vulgaris extract was mainly composed by thymol (38.73%), carvacrol (19.31%), β-cimene (10.13%) and α-terpinolene (5.94%) while Z. officinale was mainly composed by Gingerol (46.85%), cedrene (8.39%), zingiberene (7.41%) and α-curcumene (7.32%) respectively. These effective plant extracts may contribute to development of potentially effective and environmentally safer alternative fungicide to control tomato damping- off phytopathogenic fungi.

	 

	Key words: Fungicides, plant extracts, fungitoxic properties

https://academicjournals.org/journal/AJMR/article-full-text-pdf/220C0C820029.pdf

Fungicidal activities of certain methanolic plant extracts against tomato phytopathogenic fungi

Free radical scavenging action of medicinal herbs from Mongolia.

Defensive strategies in Geranium sylvaticum, Part 2: Roles of water-soluble tannins, flavonoids and phenolic acids against natural enemies

Most plants exhibit inhibitory and stimulatory biochemical interactions with other plants and microorganisms, referred to as “allelopathy.” Especially, through root exudates, higher plants are able to affect the microfiora in the rhizosphere. Production of biological active substances by higher plants that prevent phytopathogens (bacteria, fungi, and nema-todes) from infecting crops has been reported (Yoshihara et al. 1988; Schenk et al. 1991). In addition, many species of plants which have been widely used for medicinal purpose also exert an allelopathic effect (Fujii et al. 1991).

Medicinal plants for suppressing soil-borne plant diseases. II. Suppressive effect of Geranium pratense L. on common scab of potato and identification of the active compound

Jun Ushiki

Papers

Medicinal plants for suppressing soil-borne plant diseases. II. Suppressive effect of Geranium pratense L. on common scab of potato and identification of the active compound