2.7.17
BIOCONTROL OF WILT OF SACCHARUM OFFICINARUM AND ENHANCEMENT OF IN BIOMASS AND SUCROSE CONTENT BY VAM

RS BILGRAMI and K PRASAD

Department of Botany, BRA Bihar University, Muzaffarpur-842001, India

Background and objectives
Control of wilt of sugarcane caused by Fusarium sacchari and Acremonium implicatum presents a challenging area of research[1]. Vesicular-arbuscular mycorrhizae have proved to be potent symbionts in suppressing many soil-borne pathogens, conferring resistance, and increasing biomass of the associated plants [2]. An attempt has been made to examine their effect on wilt pathogens and on biomass, juice and sucrose content of the treated plants.

Materials and methods
The percentage frequency and abundance of individual organism present in rhizosphere of VAM-infected and VAM-free plants was determined by the usual method. The root exudates of the test plants were also analysed by paper chromatography. The plant dry weight, shoot length and thickness were determined by the established method. The total juice per plant was extracted and the sucrose content was estimated by using a Brix Hydrometer and Polpriscope.

Results and conclusions
The total elimination of wilt pathogens was recorded in rhizosphere soil of VAM-inoculated sugarcane plants. The frequency and abundance of other parasitic furigi were also reduced or totally suppressed, whereas dominance of saprophytic organisms significantly increased in the rhizosphere. The elimination of wild pathogens might result from the adverse effect of root exudates or induced antagonistic activity of saprophytic soil fungi, but no definitive reason can be given unless the biochemical products of the host-parasite-VAM interaction are thoroughly examined. Considerable increases in plant dry weight(32.15%), height (29.40%), stem thickness (16.60%), number of nodes per plant (37.50%), juice content per plant (38.69%) and sucrose content (12.52%) were recorded in plants inoculated with VAM compared with VAM-free plants. the increase in biomass and sucrose synthesis is possibly due to efficient uptake of less or unavailable sources of essential nutrients and changes in host physiology.

References
1. Agnihotri VP, 1996 Indian Phytopathology 49, 109-26.
2. Jalali EBL, Chand H, 1989. Mycorrhizae for Green Asia. Madras: Alamu Publications, pp. 209-215.