Histopathology of Seed-Borne Infections - Applied Research Center ...

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Seed Infection by Bacteria 189gagwbgbAcwBbFIGURE 6.9 Seed gall of Lolium rigidum caused by Rathayibacter rathayi. A, Gall colonizedby bacteria. B, Interference contrast photograph of a section through bacterial gall showingthe wall and bacteria filling the cavity. C, A part from B magnified showing the closely packedbacteria. (Abbreviations: b, bacteria; cw, cell wall; ga, gall apex; gb, gall base, gw, gall wall.)(From Bird, A.F., Stynes, B.A., and Thomson, W.W. 1980. Phytopathology 70: 1104–1109.With permission.)C
190 Histopathology of Seed-Borne Infections1932). Embryos in infected seeds are occasionally surrounded by bacterial masses(Schuster and Smith, 1983).6.2.5 PANTOEAThe genus, Erwinia, has two major groups of plant pathogenic species, viz., thepectolytic bacteria that cause soft rot (often placed in Pectobacterium) and bacteriathat cause necrosis and wilt have been reorganized into Enterobacter, Erwinia, andPantoea Gavini. The two species Enterobacter stewartii and E. herbicola, known tocause seed infection in corn and rice, have been transferred to Pantoea.Ivanoff (1933) has reported the location of Pantoea stewartii subsp. stewartii inthe tissues of corn kernel. The bacterium occurs in the chalazal tissues, between thechalazal tissue and endosperm and in endosperm. In the chalazal region, it occursin spiral vessels, sometimes completely plugging them, and after breaking throughthe vessel walls, forms cavities in the surrounding parenchyma. After disrupting theinner epidermis, the bacterium invades the space between the chalazal tissue andaleurone layer and the inner layers of the endosperm. Earlier Rand and Cash (1921)isolated P. stewartii subsp. stewartii from the endosperm of infected corn seeds.Pepper (1967) also concluded that P. stewartii subsp. stewartii is internally locatedin seed.Pantoea agglomerans, a causal agent of bacterial palea browning of rice, infectsthe lemna and palea through the stomata (Tabei, Azegami, and Fukuda, 1988). Itmultiplies in intercellular spaces, and browning occurred only of the parenchymatoward the inner surface in the palea. The browning of palea is suspected to be adefense reaction.6.3 SURVIVAL IN SEEDThe seed-borne bacteria do not form spores. Some bacterial pathogens die beforethe seed loses its viability, while many others survive even beyond the time of seedgerminability. Skoric (1927) found that P. s. pv. pisi survives in pea seed for at least10 months. X. o. pv. oryzae in rice seeds is also short-lived, only 2 to 6 months(Kauffman and Reddy, 1975; Trimurthy and Devadath, 1984). X. o. pv. oryzicolaand X. a. pv. phaseoli survive in rice and bean seeds, respectively, from one seasonto another (Zaumeyer, 1930; Shekhawat and Srivastava, 1972a,b). Zaumeyer andThomas (1957) reported that C. f. pv. flaccumfaciens was viable after 5 to 24 yearsin bean seeds. Schuster and Sayre (1967) isolated virulent C. f. pv. flaccumfaciensvar. aurantiacum, X. a. pv. phaseoli and its pigmented var. fuscans from 15-yearoldbean seeds. Basu and Wallen (1966) found X. a. pv. phaseoli viable in beanseeds after 3 years at 20 to 35°C and nonviable in another sample of 2-year-oldseeds, revealing the variability in its viability. Acidovorax avenae subsp. avenae wasfound to survive in rice seed lots stored for 8 years at 5°C (Shakya, Vinther, andMathur, 1985).Pantoea stewartii subsp. stewartii survived and was pathogenic when isolatedfrom 1-year-old maize kernels. This bacterium has another very interesting mechanismof survival and transmission of the disease. P. stewartii subsp. stewartii survives
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Histopathology ofSeed-Borne Infecti
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PrefaceThe book deals with only one
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The AuthorsDalbir Singh, Ph.D., for
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ContentsChapter 1 Introduction ....
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4.3.2 Routes for Infection from Ova
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8.4 Survival in Seed ..............
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2 Histopathology of Seed-Borne Infe
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4 Histopathology of Seed-Borne Infe
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2Reproductive Structuresand Seed Fo
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Reproductive Structures and Seed Fo
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14 Histopathology of Seed-Borne Inf
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3Structure of SeedsThe seed habit i
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Structure of Seeds 49(1971) of usin
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Structure of Seeds 51is found in as
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Structure of Seeds 53dry seed of Ly
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Structure of Seeds 553.3.2 SEED COA
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Structure of Seeds 57Endosperm: One
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Structure of Seeds 59scendembepsmuA
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Structure of Seeds 61Endosperm: Sca
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Structure of Seeds 63Chalaza simple
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Structure of Seeds 65stystypmerA Bc
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Structure of Seeds 67epsent endCADB
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Structure of Seeds 69perhscendembpe
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Structure of Seeds 71eposgepi′epo
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Structure of Seeds 73(Zea and Sorgh
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Structure of Seeds 75Baker, D.M. an
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Structure of Seeds 77Maheshwari Dev
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Structure of Seeds 79Vries, M.A. de
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100 Histopathology of Seed-Borne In
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Page 232 and 233: Seed Infection by Viruses 2177.4.2
Page 234 and 235: Seed Infection by Viruses 219seed(s
Page 236 and 237: Seed Infection by Viruses 221AMV fo
Page 238 and 239: Seed Infection by Viruses 223REFERE
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