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15.3a. Pseudomonas glumae on nutrient agar (blue background). b. Seedling rot (P. glumae) after inoculation. The two healthy seedlings at both sides are the controls. c. Grain rot d. Infected grains. Top = dehulled grain, bottom = whole grain (courtesy of C.C. Chien). e. Infected spikelets are unevenly distributed in the affected panicle (courtesy of C.C. Chien). Pseudomonas glumae Pathogen: Pseudomonas glumae Kurita and Tabei (Etymology: from Greek pseudes, false; monas, unit; glumae refers to glume) Disease: bacterial grain rot Detection level: frequently detected, with moderately high epidemic potential Where detected: infected seeds and rot ten seedlings How detected: see Chapter 7. Appearance: see Figure 15.3. See Chapter 7 and Figure 15.3a for a comparison of P. avenae, P. glumae, P. fuscovaginae, and P. syringae, pv. syringae. THE DISEASE—BACTERIAL GRAIN ROT The disease occurs widely (Kaku 1988, Zeigler and Alvarez 1988). Infection causes spikelet sterility and poor or no grain ripening. There is no exact estimate of losses caused, but 900,000 ha of rice in North Kyushu Island (Japan) have been infected, indicating the intensity and severity the disease can assume (Mew et al 1989). Symptoms Bacterial grain rot symptoms appear on seedlings and spikelets. Seedlings raised in boxes turn brown and rot (Fig. 15.3b). The glumes (lemma) of infected spikelets are discolored. Initially dirty gray, they turn yellow brown, then become dark brown and shrunken, and ultimately dry (Fig. 15.3c). in mild infections, only the palea discolor. Brown bands can be seen distinctly over the belly of the infected kernel (Fig. 15.3d). Infected spikelets are unevenly distributed in an affected panicle (Fig. 15.3e). In severe infections, 50% of spikelets may be affected. The bacterium is active only in spikelets but spreads intercellularIy in the lemmal tissues. Disease development Irrigated tropical ecosystems support development of bacterial grain rot. The disease prospers in high temperature and humidity. Bacterial grain rot usually occurs at the milk stage. Infections occurring at heading stage are more damaging. Control Treating seeds with dry heat at 65 °C for 6 d helps eliminate P. glumae from seed (Zeigler and Alvarez 1988). Pseudomonas syringae pv. syringae Pathogen: Pseudomonas syringae pv. syringae van Hall. (Syn P. oryzicola Klement) (Etymology: from Greek pseudes, false; monas, unit; syringae from Syringa, generic name of lilac) Disease: bacterial sheath rot Detection level: frequently detected, with low epidemic potential Where detected: infected seeds, rotting flag sheaths, stem, node How detected: see Chapter 7. (No specific detection method.) Appearance: see Figure 15.4. 15.4 Pseudomonas syringae pv. syringae on nutrient agar. Bacterial pathogens 93
See Chapter 7 and Figure 15.4a for a comparison of P. avenae, P. glumae, P. fuscovaginae, and P. syringae pv. syringae. THE DISEASE—BACTERIAL SHEATH ROT Bacterial sheath rot was first reported by Klement (1955) in Hungary as a new bacterial rice disease affecting the panicle leaf sheath. Bacterial sheath rot occurs now in ricegrowing continents and seems to have worldwide distribution. The causal bacterium may be present simultaneously with other Pseudomonas spp. Symptoms The infected panicle sheath develops brown lesions which later rot and cause the panicle to dry. The stem and nodes may develop blurred spots which turn brown or black (Ou 1985). Grains become discolored. Spikelets of infected panicles become sterile. Disease development Bacterial sheath rot primarily occurs in irrigated environments. Wet and windy weather helps spread the disease (Klement 1955). The disease may be seedborne and seed-transmitted, and may spread in a field through rain splash. Both hypotheses need confirmation. Although the disease frequently occurs at the heading stage, it may develop earlier. Control Treating seeds with dry heat at 65 °C for 6 d helps eliminate P. syringae pv. syringae from seed (Zeigler and Alvarez 1988). Xanthomonas oryzae pv. oryzae Pathogen: Xanthomonas oryzae pv. oryzae (Ishiyama 1922, Dye 1978, Dye et al 1980) (Etymology: from Greek xanthus, yellow; monas, unit; oryza, rice) Disease: bacterial blight Detection level: infrequently detected, with high epidemic potential Where detected: seeds and other diseased plant parts How detected: see Chapter 7. (Note that detection methods are not standardized for Xoo.) Appearance: see Figure 15.5. See Chapter 7 and Figure 15.5a for a comparison between X. oryzae pv. oryzae and X. oryzae pv. oryzicola. THE DISEASE—BACTERIAL BLIGHT Bacterial blight is one of the most destructive rice diseases in Asia. It occurs in China, Korea, India, Indonesia, Philippines, Sri Lanka, Taiwan, Thailand, and Vietnam. The disease also occurs in Northern Australia and Africa. Symptoms In the tropics, bacterial blight exhibits three distinct symptoms. Leaf blight symptom is the most common manifestation seen in the farmer's field (Fig. 15.5b). Watersoaked stripes appear a few centimeters below the leaf tip, on the margin of the leaf blade (Fig. 15.5c). Stripes enlarge and turn yellow within a few days. They have wavy margins. One or both leaf margins may have lesions. As the disease progresses, lesions cover the whole leaf and the leaf turns white to gray with an overgrowth of saprophytic fungi. 15.5a. Xanthomonas oryzae pv. oryzae colonies on nutrient agar. b. Field symptoms of bacterial blight. c. Water-soaked stripes on leaves. d. Bacterial ooze. 94 Rice seed health testing manual
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A Manual of Rice Seed Health Testin
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Contents Foreword v Preface vi Part
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Foreword Intensive collaboration ch
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Part 1 Introduction CHAPTER 1 Rice
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tional levels (Kahn 1988). Quaranti
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Morphology of the mature plant Matu
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two-celled, besifixed, deeply sagit
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Part 2 Procedures for seed health e
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CHAPTER 3 Equipment J.K. Misra, T.W
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3.2 Dry seed inspection using a mag
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Example. In a two-stage random samp
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solid pointed end. The tube and sle
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CHAPTER 5 Dry seed inspection J.K.
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Detection Blotter and agar plate me
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Results: Examine plates for charac-
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Extraction and isolation It is esse
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GRINDING METHOD (FOR SMALL-SCALE SE
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flagellum. Cells occur singly, in p
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7.6 Oxidase test reaction. L = colo
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7.9 Production of 2-ketogluconate.
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1. Grow pathogen-free plants under
Page 49 and 50: 7.12 a. P. glumae type A colony on
Page 51 and 52: A1. Macerate 100 seeds in 10 ml of
Page 53 and 54: Results: 7.Streak the bacteria onto
Page 55 and 56: Sieve method (Fig. 8.1) Procedure:
Page 58 and 59: CHAPTER 10 Field inspection J.K. Mi
Page 60 and 61: Table 10.2. continued Disease Fungi
Page 62 and 63: Table 10.2. continued Disease Growt
Page 64: additional precaution, the multipli
Page 67 and 68: terracoat (5-ethoxy-3- trichloromet
Page 70: Part 3 Pests and pathogens CHAPTER
Page 73 and 74: elevant tests for determining the i
Page 75 and 76: Table 12.1 continued Family and spe
Page 77 and 78: Cryptolestes pusillus Schonherr The
Page 79 and 80: Rice weeviI Scientific name: Sitoph
Page 82 and 83: CHAPTER 14 Fungal pathogens J.K. Mi
Page 84 and 85: THE DISEASE—BROWN SPOT Sir John W
Page 86 and 87: Symptoms Glumes are discolored, and
Page 88 and 89: y low relative humidity. Released a
Page 90 and 91: THE DISEASE—STEM ROT Stem rot was
Page 92 and 93: THE DISEASE—SHEATH BLIGHT Sheath
Page 94 and 95: Sarocladium oryzae is seedborne. Th
Page 96: Although not currently considered a
Page 99: Pseudomonas fuscovaginae Pathogen:
Page 103 and 104: Infected seeds and contaminated wat
Page 105 and 106: For further details, see the Common
Page 107 and 108: nonfluorescent) and Erwinia herbico
Page 109 and 110: Franklin M T, Siddiqi M R (1972) Ap
Page 111 and 112: Tai F L, Siang W N (1948) 'I-chu-hs
Page 113 and 114: 106 Rice seed health testing manual
Page 115 and 116: 108 Rice seed health testing manual
Page 117 and 118: After autoclaving the medium, add t
Page 119 and 120: smoniloid = having swellings at reg
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