Isolation and biochemical characterizations of the bacteria ( Acidovorax avenae subsp. avenae ) associated with red stripe disease of sugarcane

Studies on Acidovorax avenae subsp. avenae, associated with red stripe disease of sugarcane was conducted in the Department of Plant Pathology, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi during 2009 to 2010, in collaboration with Shakarganj Sugar Research Institute (SSRI), Jhang, Pakistan. Red stripe of sugarcane were recently observed on promising clones of sugarcane planted in autumn 2009 at Ashaba Research Farm of SSRI. Bacteria were isolated from diseased plants. These isolates yielded off white convex colonies on potato dextrose agar (PDA) media at 29 degrees C with 1.7 to 1.9 mm diameter and were yellow on yeast extract dextrose chalk agar (YDC) media at 27 degrees C with 1.8 to 2.0 mm diameter. The bacteria were rod shape measuring 0.5 to 0.6 x 1.4 to 1.6 mu m on PDA and 0.6 to 0.7 x 1.5 to 1.7 mu m on YDC. Bacterial culture was stored at different temperature levels for 150 days. Re-isolation of bacterial culture which was stored at 4 degrees C showed best result on YDC at 27 degrees C after 150 days, whereas it showed positive result after 120 days on PDA at 29 degrees C. Bacteria were gram negative, citrate utilization was positive, oxidase was negative, catalase was positive and urease was negative. Morphological appearance and biochemical characterizations identified the bacteria as A. avenae subsp. Avenae. In vitro screening for the efficacy of various antibiotics to inhibit the growth of A. avenae subsp. avenae on YDC media showed that ampicillin and vancomycin were most effective. Artificial inoculation on sugarcane against red stripe disease was observed. Observations were made upto six weeks for disease development. Out of 27 varieties, 16 were found resistant, four moderately resistant, five moderately susceptible and two susceptible.