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

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Seed Infection by Bacteria 183FIGURE 6.6 (Color figure follows p. 146.) Pigeon pea (Cajanus cajan) seeds healthy (upperrow) and infected with Xanthomonas axonopodis pv. cajani. Seeds moderately shriveleddiscolored(middle row) and heavily shriveled-discolored (lower row) with water-soakedtranslucent areas. (From Sharma, M. et al. 2001. J. Mycol. Plant Pathol. 31: 216–219.)The embryo remained free of infection. Moderately shriveled and discolored seedscarried infection in all the layers of seed coat and superficial layers of the cotyledons(Figure 6.7A, D). Bacteria occurred inter- and intracellularly and were present inthe stellate parenchyma and persistent part of funiculus (Figure 6.7C). Affectedcotyledonary cells also showed necrosis. Heavily infected seeds had infection in allparts including parts of the embryo (Figure 6.7B). Bacterial masses occurred in theseed coat (Figure 6.7E), stellate parenchyma, and remnants of the funiculus. Necrosisand formation of the lytic cavities, occupied by bacterial cells, were seen. Spacesin seed, between the seed coat and embryo, between the cotyledons, and around theshoot-root axis also contained bacteria. Bacteria also occurred intracellularly incotyledonary cells (Figure 6.7F) and caused depletion of cell contents includingstarch grains, which were small and only of the simple type (simple and compoundstarch grains in unaffected cotyledons).X. axonopodis pv. malvacearum, a causal organism of bacterial blight, angularleaf spot, or black arm of cotton, occurs externally and internally in seed. Internalinfection was detected in the micropylar as well as chalazal halves of the seed coats,and rarely in the embryo (Tennyson, 1936; Brinkerhoff and Hunter 1963). Brinkerhoffand Hunter (1963) tried to determine the course of entry of the bacterium intothe seed. They soaked ginned fuzzy seeds of several varieties of cotton in aqueousdye (light green) and aqueous suspension of the bacterium. The dye readily enteredthrough the blunt chalazal end, and only after the embryo swelled, entered through
184 Histopathology of Seed-Borne InfectionsracpsccotpalChgcABDbhgcsgEFFIGURE 6.7 Histology of normal and Xanthomonas axonopodis pv. cajani-infected pigeonpea seeds. A, Ts seed through hilar region. B, Ts shriveled and discolored seed showingpresence of bacterial masses in different parts of seed. C, Section of part of funiculus havingbacterial masses in cells. D, Ts part of seed coat with bacterial cells in hourglass cells andinner parenchymatous cells. E, Ts part of seed coat from heavily infected seed. Hourglasscells are distorted and possess bacterial masses. F, Inter- and intracellular colonies of bacteriain cells of cotyledon. Starch grains are surrounded by bacteria and show corrosion. (Abbreviations:b, bacteria; cot, cotyledon; cp, counter palisade; hgc, hourglass cells; pal, palisadecells; ra, rim aril; sc, seed coat; sg, starch grains.) (A, B, E, F, From Sharma, M. et al. 2001.J. Mycol. Plant Pathol. 31: 216–219; C, D, From Sharma, M. 1996. Ph.D. thesis, Universityof Rajasthan, Jaipur, India.)the micropylar end. Similarly, the causal bacterium entered the fuzzy seed throughthe chalazal end. It may be mentioned that the stomata are aggregated in the surfaceof the chalaza.Crossan and Morehart (1964) isolated X. vesicatoria from vascular and corticaltissues of pedicel, ovary and seed of Capsicum annuum. SEM studies of artificiallyinoculated stalks and mature fruits of Golden King plum with X. arboricola pv.pruni (X. c. pv. pruni) have shown that the vascular elements of the stalk, mesocarp,stony endocarp, and seed are filled with masses of the bacterium (Du Plessis, 1990).
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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
Page 240 and 241: Seed Infection by Viruses 225Hunter
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