Comparative evaluation of composts and dried powdered biomass of botanicals for organic management of downy mildew of sorghum

The biomass of 10 selected botanicals was evaluated as soil amendments, in the form of composts and dry powder biomass, to compare their potential to suppress downy mildew disease caused by oosporic inoculum of Perenosclerospora sorghi. Eight botanicals (Allium cepa, Lantana camara, Polyalthia longifolia, Hyptis suaveolens, Azadirachta indica, Nerium oleander Eucalyptus globulus and Tamarindus indica) proved effectively in the form of dry biomass powder at 4% (w/w) rate to control infection by oospores, while two (Croton sparsiflorus and Tagetes erecta) promoted it. In the form of composts (2% rate), the efficacy of botanicals was generally found reduced with the appearance of more disease than negative control in case of all botanicals except one (A. cepa). At the 4% compost rate, only four botanicals namely, A. cepa, P. longifolia, H. suaveolens and L. camara were found to suppress the disease. At higher amendment rates of 6, 8 and 10%, six botanicals suppressed the disease. Dry powders are not only superior in disease suppression but confer additional benefits like reduced bulk, increased shelf life, consistent composition and results

Screening of plant extracts for organic management of downy mildew of sorghum

Antipathogenic potential of 38 plants was evaluated in the form of aqueous extracts against Peronoclerospora sorghi, causing downy mildew of sorghum. Conidial suspension and plant extracts were mixed individually and allowed to stand for 5 min and then used to inoculate the host by sprout-dip method. The sprouts thus inoculated were grown in pots, and the disease incidence was observed. Eight plant extracts (Cicer areatinum, Datura metel, Croton sparsiflorus, Parthenium hysterophorus, Nerium oleander, Chromolaena odorata, Duranta repens and Oxalis latifolia) at 20% concentration performed at par with chemical fungicide (Mancozeb 75%) by exhibiting total suppression of disease incidence to 0%, when compared with 64.1% of negative control. Organic management of air-borne inoculum of downy mildew of sorghum is feasible and preferable when compared with chemical control methods, considering human and environmental health concerns. The use of water extract keeps the technology simple so that it can be directly prepared and used by the farmers. Short-listing of eight most effective water extracts would help in self-reliance of farmers, reducing their dependence on commercial products

Comparative evaluation of long-term storage techniques on viability and virulence of alternaria solani

he study was conducted to test the viability and pathogenicity of different forms of Alternaria solani inoculum stored at different conditions and time intervals for a period of 16 months. The aim was to confirm the survival period of pathogen in soil and to determine the simplest method to maintain inoculum in laboratory for further studies. The cultures stored at 5 °C for 2, 4, 8 and 16 months were pathogenic, while cultures stored at room temperature turned non-pathogenic after 4 months. All 6 successive sub-cultures retained viability and virulence. All the target-spots stored at 5 °C were viable after all time intervals as tested by culturing and subsequent spray of harvested mycelial suspension, but at the room temperature (RT), 16 months old inoculum lost viability and virulence. The powdered tissue samples of target-spots stored at 5 °C were found pathogenic by spray method after all the intervals of the time but, at RT 16 month old sample lost virulence. In inoculation by soil splashing, powdered tissue stored in paper bag at 5 °C retained pathogenicity till 8 months, while at RT, the inoculum stored in paper bags and the inoculum mixed in soil lost pathogenicity after 4 months

Durantol - a phytosterol antifungal contributor from duranta repens linn. for organic management of sorghum downy mildew

Downy mildew of sorghum (DMS) has serious implications agronomically worldwide and to-date the search for a potent fungicide is a high priority and necessity. Phytochemicals have proven to be effective against various plant pathogens with minimal or no side effects. Duranta repens aqueous extract exhibited a promising potential as an organic fungicide for management of sorghum downy mildew (Peronosclerospora sorghi) in greenhouse conditions, at low concentration of 5 %. Activity guided bio-prospecting lead to the isolation of active principle which could control the DMS at as low as 0.1 % concentration. Spectral studies identified the bioactive contributor as a phytosterol namely 16-Hydroxy-8,10,13-trimethyl-1,2,8,10,12,13,14,15-octahydro cyclopenta [a] phenanthren-3-one, designated as Durantol. The results of microscopy exhibited the inhibition of conidial germ-tube growth by formation of bulb-like swellings at the tip, suggesting the mechanism of action of Durantol was via hampering the membrane integrity of the pathogen. Further, the same was virtually predicted using molecular docking for structure-activity relationship (SAR) against four best known membrane receptors namely 1-UDP-glycosyltransferases (UGT), cytochromes P450 (P450), oxidosqualene cyclase (OSC) and serine carboxypeptidase-like acyltransferase (SCPL), proposing that glycosylation onto the membrane would be a reason for inhibition and which is evident from atomic contact energy (ACE) values. The results of the study indicate that, organic management of airborne inoculum of downy mildew of sorghum is feasible and preferable, as compared to the use of chemical fungicides, considering human and environmental health concerns