Bacteria - finger millet
Contributors to this page: ICRISAT, Patancheru, India (RP Thakur, AG Girish, VP Rao).
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Brown spot; Bacterial brown spot
Scientific name
Pseudomonas syringae pv. syringae.
Other scientific names
Pseudomonas syringae pv. japonica
Importance
High
Significance
The disease is very important throughout the world where finger millet is grown.
Symptoms
Symptoms first appear on the lower surface of the leaves as small, water-soaked spots. The spots enlarge, coalesce, and form larger areas that later become necrotic. The bacteria also enter the vascular tissues of the leaf and spread into the stem. The infected area, which is surrounded by a narrow zone of bright, lemon yellow tissue, turns brown, becomes rapidly necrotic, and through coalescence of several small spots, may produce large dead areas of various shapes. The disease produces identical symptoms on the stems, pods and seeds. In addition, light-cream or silver bacterial exudates are often produced on the lesions under moist conditions.
Hosts
Multilateral hosts like graminacious and leguminacious plants.
Geographic distribution
Pseudomonas syringae pv. syringae is worldwide in distribution.
Distribution of Pseudomonas syringae pathovars into twenty-three O serogroups [online].
Biology and transmission.
Pseudomonas syringae pv. syringae is a rod shaped, gram-negative with polar flagella. It tests negative for arginine dihydrolase and oxidase activity, and forms the polymer levan on sucrose nutrient agar. It is known to secrete the lipodepsinonapeptide plant toxin syringomycin, and it owes its yellow fluorescent appearance when cultured in vitro on King's B medium to production of the siderophore pyoverdin (Goszczynska and Serfontein 1998). Pathogen is seed borne and spreads through the infected seed from season to season (Gaudet and Kokko 1986; Venette et al. 1987).
Detection/indexing methods at ICRISAT
- Pre-export field inspection and agar plate method are used.
Treatment/control
- No suitable seed treatment to eradicate infection
Procedures followed in case of positive test at ICRISAT
- So far not detected at ICRISAT.
References and further reading
Duveiller E, Rudolph K, Fucikovsky L. (eds.). 1997. The Bacterial Diseases of Wheat: Concepts and Methods of Disease Management, Mexico, D.F.: CIMMYT, 78p.
Gaudet DA, Kokko EG. 1986. Seedling disease of sorghum grown in southern Alberta caused by seed borne Pseudomonas syringae pv. syringae. Canadian Journal of Plant Pathology 8: 208-217.
Goszczynska T, Serfontein JJ. 1998. Milk-Tween agar, a semi selective medium for isolation and differentiation of Pseudomonas syringae pv. syringae, Pseudomonas syringae pv. phaseolicola and Xanthomonas axonopodis pv. phaseoli. Journal of Microbiological Methods 32: 65-72.
Mew TW, Misra JK. (eds.). 1994. A Manual of Rice Seed Health Testing. International Rice Research Institute (IRRI), Manila, Philippines, 113pp.
Venette JR, Lampa RS, Albaugh DA, Nayes JB. 1987. Presumptive procedure (dome test) for detection of seed borne bacterial pathogens in dry beans. Plant Disease 71: 984-990.
Scientific name
Xanthomonas vasicola pv. holcicola Elliott.
Other scientific names
Bacterium holcicola, Phytomonas holcicola, Pseudomonas holcicola, Xanthomonas campestris pv. holcicola, Xanthomonas holcicola
Importance to CGIAR centers
High
Significance
Bacterial streak is of minor importance on finger millet.
Symptoms
Symptoms caused by the pathogen are narrow, water-soaked, transparent leaf streaks, 2-3 mm wide by 2-15 mm long, appearing as early as the second leaf stage of the seedling. Lesions soon turn red, become opaque, and at intervals may broaden into somewhat irregularly shaped oval spots with tan centers and narrow red margins. In severe attacks, lesions coalesce to form long irregular streaks and blotches extending across all or much of the leaf blade, with dead tissue bordered by narrow, dark margins between the reddish-brown streaks. Abundant bacterial exudate is produced as light-yellow droplets, which dry to thin white or cream scales (Williams et al. 1978).
Hosts
Panicum miliaceum (millet), Setaria italica (foxtail millet), Sorghum halepense (aleppo grass), Sorghum sudanense (Sudan grass) and Sorghum bicolor (common sorghum).
Geographic distribution
Worldwide
Biology and transmission
Soilborne and infected plant debris transmit the bacteria. Seed transmission of the pathogen is not known so far.
Detection/indexing methods at ICRISAT
- Pre-export field inspection.
Treatment/control
- No seed treatment.
Procedures followed in case of positive test at ICRISAT
- So far not detected.
References and further reading
Williams RJ, Frederiksen RA, Girard JC. 1978. Sorghum and Pearl Millet Disease Identification Handbook. Information Bulletin No. 2. ICRISAT, Patancheru 502324, AP, India. 51pp.
Scientific name
Xanthomonas campestris (Pammel) Dowson
Other scientific names
Xanthomonas pennisiti, Xanthomonas annamalaiensis, Xanthomonas rubrisorghi.
Importance to CGIAR centers
High
Significance
Bacterial leaf streak is of minor importance.
Symptoms
Initial symptoms are narrow, water-soaked, transparent leaf streaks; 2-3 mm wide by 2-15 mm long generally appear from second leaf stage of the seedlings. Lesions soon turn red, become opaque, and at intervals may broaden into somewhat irregularly shaped oval spots with tan centers and narrow red margins. In severe attacks, these coalesce to form long irregular streaks extending across the leaf blade. Abundant bacterial exudates are produced as light-yellow droplets, which dry to thin white or cream scales (Williams et al. 1978).
Hosts
Pearl millet and proso millet (Panicum miliaceum).
Geographic distribution
It is reported from Nigeria and Senegal.
Biology and transmission
Bacterial colonies are yellow and mucoid on the nutrient agar medium. Bacterial cells are aerobic, motile, gram-negative, rod-shaped which differ pathologically, serologically, and by membrane protein patterns from other pathovars of X. campestris. Cells measure 0.45 ´ 2.25 mm and have one polar flagellum. Optimal growth occurs between 26 and 30 oC (Rangaswami et al. 1961).
Detection/indexing methods at ICRISAT
- Pre-export field inspection and agar plate method are used.
Treatment/control
- No seed treatment is available.
Procedures followed in case of positive test at ICRISAT
- So far not detected.
References and further reading
Rangaswami G, Prasad NN, Eswaran KSS. 1961. Two new bacterial diseases of sorghum. Andhra Agricultural Journal 8:269-272.
Williams RJ, Frederiksen RA, Girard JC. 1978. Sorghum and Pearl Millet Disease Identification Handbook. Information Bulletin No. 2. ICRISAT, Patancheru 502324, AP, India. 88pp.
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