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

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Penetration and Establishment of Fungi in Seed 89ABCDFIGURE 4.5 Infection of Cucumis sativus stigma and ovule by Didymella bryoniae afterartificial inoculation. A, SEM photomicrograph of stigma showing papillae and germinatingconidia, 4 hours after inoculation. B, Ls of stigma showing papillae and hyphae (arrows) after48 hours of inoculation. C, Part of pericarp and chalazal region of ovule showing hyphaetransversing the gap between the pericarp and ovule, and pentrating the epidermis of the outerintegument. D, Ls of part of ovule with hyphae (arrow) in nucellus. (From Neergaard, E.1989. Can. J. Plant. Pathol. 11: 28–38. With permission.)4.3.1.2.2 Ovary and Fruit WallFungal inoculum may reach the ovary and developing fruit wall from outside afterthe flower has bloomed in hypogynous flowers. It may reach them easily when thenonessential whorls (sepals and petals) have dropped. The inferior ovary, which
90 Histopathology of Seed-Borne Infectionsremains exposed from initiation, can get infected at any stage during the development.The infection may be localized, forming lesions or progressive discoloration,or it may remain symptomless. The pathogens may penetrate the ovary wall throughthe cuticle, epidermal cells, stomata, cracks, hairs, and nectaries, if any (Figure 4.3A,B).The course of infection of loose smut of wheat and barley seems to exemplifythis type of infection, although there is no general agreement (Brefeld, 1903;McAlpin, 1910; Lang, 1910, 1917; Ruttle, 1934; Simmonds, 1946; Batts, 1955;Pederson, 1956; Shinohara, 1972). Using artificially inoculated and naturallyinfected ears of wheat by Ustilago tritici, Batts (1955) concluded that despiteplentiful spores on the stigma, the spores caught on the ovary germinated, and hyphaepenetrated the ovary wall directly. Stomata occur in the ovary wall, but entry of thehyphae through them was not seen. Malik and Batts (1960), who studied infectionof barley ears by U. nuda, also found numerous spores on the stigma and style, butobserved that spores caught on the ovary surface alone caused infection.Localized infection of the fruit wall causing internal infection of the locule iscommon (Neergaard, 1979; Agarwal and Sinclair, 1997). This has been reported forsiliqua and seed infection of cabbage by Phoma lingam (Bonman and Gahrielson,1981), pod infection of soybean by Phomopsis longicola (Roy and Abney, 1985),and infection of sugar beet flower and seed bolls by Colletotrichum dematium f.spinaciae (Chikuo and Sugimoto, 1989). In artificially inoculated cotton bolls withColletotrichum capsici, Roberts and Snow (1984) observed that conidia germinatedon the fruit wall and penetrated directly or through the stomata and hairs (Figure4.6A to D). Hyphae invaded the pericarp parenchyma, the vascular system, endocarp,and lint fibers. Conidia of Colletotrichum gloeosporioides, after artificial inoculationof Carica papaya green fruits, germinated and penetrated the cuticle and epidermalcells (Chau and Alvarez, 1983).4.3.1.2.3 Other Floral Parts Including NectaryAlthough the necrotrophs often attack senescing nonessential floral parts (Jarvis,1977), the exact role of this type of infection, including that of floral nectaries incausing fruit and seed infection, is little understood. Colletotrichum lini and Aureobasidiumlini infect senescing petals in linseed flowers and developing fruits(Lafferty, 1921; Johansen, 1943). Davis (1952) found that Acronidiella eschscholtziaeon Eschscholtzia californica penetrates the capsule from infected petals throughthe fruit stalk. Infection of barley caryopsis by Rhynchosporium secalis occurscommonly on the inside of the lemma just below the base of the awn and rarely onthe inside of the palea. This infection subsequently spreads to the portion of thepericarp in contact with the infected regions of the lemma and palaea (Skoropad,1959). Neergaard (1989) has observed the invasion of cucumber ovaries through thenatural openings in the nectary by D. bryoniae and presumed that this infection mayspread to the transmitting tissue inside the ovary.
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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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Reproductive Structures and Seed Fo
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14 Histopathology of Seed-Borne Inf
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Page 53 and 54: 38 Histopathology of Seed-Borne Inf
Page 56 and 57: Reproductive Structures and Seed Fo
Page 62 and 63: 3Structure of SeedsThe seed habit i
Page 64 and 65: Structure of Seeds 49(1971) of usin
Page 66 and 67: Structure of Seeds 51is found in as
Page 68 and 69: Structure of Seeds 53dry seed of Ly
Page 70 and 71: Structure of Seeds 553.3.2 SEED COA
Page 72 and 73: Structure of Seeds 57Endosperm: One
Page 74 and 75: Structure of Seeds 59scendembepsmuA
Page 76 and 77: Structure of Seeds 61Endosperm: Sca
Page 78 and 79: Structure of Seeds 63Chalaza simple
Page 80 and 81: Structure of Seeds 65stystypmerA Bc
Page 82 and 83: Structure of Seeds 67epsent endCADB
Page 84 and 85: Structure of Seeds 69perhscendembpe
Page 86 and 87: Structure of Seeds 71eposgepi′epo
Page 88 and 89: Structure of Seeds 73(Zea and Sorgh
Page 90 and 91: Structure of Seeds 75Baker, D.M. an
Page 92 and 93: Structure of Seeds 77Maheshwari Dev
Page 94: Structure of Seeds 79Vries, M.A. de
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140 Histopathology of Seed-Borne In
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TABLE 5.6Location of Mycelium of St
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7Seed Infection by VirusesViruses a
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Seed Infection by Viruses 201TABLE
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Seed Infection by Viruses 205Unlike
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Seed Infection by Viruses 2073. The
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Seed Infection by Viruses 209Wilcox
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Seed Infection by Viruses 213floret
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Seed Infection by Viruses 215ptowvv
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Seed Infection by Viruses 2177.4.2
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Seed Infection by Viruses 219seed(s
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Seed Infection by Viruses 221AMV fo
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Seed Infection by Viruses 223REFERE
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Seed Infection by Viruses 225Hunter
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Seed Infection by Viruses 227Wolf,
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