Abstract
The causal agents of bacterial blight in lupine (Lupinis termis) were isolated from leaves displaying symptoms in Minia governorate, Egypt. The pathogens were characterized by biochemical and physiological tests, and identified as Bacillus megaterium. Tissue extracts prepared from experimentally diseased shoot systems showed great pectolytic and cellulolytic activities while healthy tissue extracts of both organs showed slight activities of the enzymes. In varietal response test, four lupine cultivars that is, Australian, Balady, Giza 1 and Giza 2 were tested for their susceptibility to all tested B. megaterium isolates and the cultivar Balady was most sensitive to all isolates. However, isolates B2 and B6 were more virulent than the others. Two isolates of B. megaterium isolates that caused blight on lupine plants were subsequently tested on other foliar plants representatives of 17 plant species. Both B. megaterium isolates could not infect any of the tested plants but produced small necrotic spots on faba bean leaves. These results indicate the host specificity of this bacterium towards its host plant and accordingly justify the suggested forma specials lupini to be given to the lupine bacterial pathogen B. megaterium. According to the literature review, this is the first report on the occurrence of B. megaterium as a causal agent of leaf blight of lupine plants in Egypt. Key words: Bacillus megaterium, lupine, pectolytic and cellulolytic activities, cultivars.
Highlights
Lupine (Lupinus termis Forsk) is one of the oldest field crops grown in Egypt
Isolation trials carried out from diseased specimens taken from lupine or spotted/ blighted foliar on sucrose nutrient agar media resulted in development of 6 bacterial isolates that was purified and kept in agar slants
Lupine plants inoculated with purified bacterial isolates behaved aggressively towards the inoculated plants
Summary
Lupine (Lupinus termis Forsk) is one of the oldest field crops grown in Egypt. Lupine uses as fodder crop and green manure for sandy and poor soils to reclaim new lands. The seeds of lupine contain great ratio of proteins, fibers and carbohydrates. It is used for medical and industrial purposes (Maknickiene, 2001). Lupine plants are prone to many diseases which attack the foliar parts causing downy mildew, rust and leaf blight diseases (Paulitz and Cote, 1991; Yang and Sweetingham, 2002). Such diseases are destructive and cause great loss in seed yield and quality (Osman et al., 1986; Muller et al, 1999). Direct involvements of pectic and cellulitic enzymes produced by the pathogen in pathogensis were reported (Gaber et al, 1990; Walker et al, 1994)
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