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

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Penetration and Establishment of Fungi in Seed 85inflorescence axis is directly infected from the mother plant. The mycelium subsequentlyinvades floral primordia (Figure 4.2A) and enters anthers and ovaries. However,secondary infection by conidia may take place through the stigma, style, orovary (Prabhu, Safeeulla, and Shetty, 1983). Muralidhara Rao, Prakash, and Shetty(1987) also found the fungal mycelium of P. sorghi in systemically infected maizeplants at all growth stages, including seeds. Fungal infection through silk and itsestablishment in seeds also occurred.Plasmopara halstedii infection in systemically infected plants of sunflowerproceeds from the receptacle to the ovary through its base. The hyphae reach thefuniculus and cause seed infection (Cohen and Sackston, 1974; Doken, 1989). Doken(1989) has shown that P. halstedii hyphae move from the receptacle to the ovarythrough intercellular spaces in the pedicel at an early ovule development stage.The mycelium of endophytic fungi also spreads intercellularly (Sampson, 1933;Philipson and Christey, 1986; Siegel, Leach, and Johnson, 1987). Using light andelectron microscopy, Philipson and Christey (1986) have provided an excellentaccount of endophyte infection in Lolium perenne. The endophyte progresses intercellularlyinto inflorescence primordium and shows acropetal growth of its hyphaeinto successively formed primordia of spikelets, florets, ovary, placenta, and ovule.In the ovary wall, hyphae rarely invade the vascular system.In barley seedlings and plants systemically infected by Drechslera graminea,the fungal hyphae spread through intercellular spaces, finally causing ear, floret, andpistil infection (Figure 4.2B to F) while the ear is still in the boot leaf stage (Thakkar,1988). The infection reaches the base of the ovary and ovule prior to the differentiationof vascular elements in these structures (Figure 4.2E, F).4.3.1.2 Indirect Infection from OutsideWhen transferred from other infected plants or from a local infection on the sameplant to the ovary or fruit, fungal spores and conidia result in indirect infection. Theinoculum may be transferred through various dispersal agencies such as wind, water(rain, irrigation), and insects. The routes for internal infection vary, depending onthe site of receipt of inoculum.4.3.1.2.1 Stigma and StyleDuring the first quarter of the 20th century, several authors reported fungal infectionthrough the stigma (Figure 4.3A) and its establishment in the seed, viz., loose smutsof barley and wheat (Lang, 1910, 1917) and anther mold of red clover, caused byBotrytis anthophila (Silow, 1933). This has been denied by later workers (Batts,1955; Jung, 1956; Campbell, 1956; Malik and Batts, 1960; Bennum, 1972). Jung(1956) inoculated stigmas of 61 plant species with numerous fungi but never foundhyphal entry into the ovary. Bennum (1972) reinvestigated B. anthophila infectionin Trifolium and found that hyphae from the stem enter the ovary and reach thefuniculus. She also observed hyphae growing acropetally from the receptacle intothe style but never saw this in the stigma.Ergot disease of grasses caused by Claviceps spp. is a classic example of blossominfection. Claviceps purpurea infects floral tissues prior to fertilization or within the
86 Histopathology of Seed-Borne InfectionsanpsfstimyowovrnyArinmyCBmyD E FFIGURE 4.2 Direct infection from mother plant. A, Ls of part of systemically infected spikeshowing spread of Sclerospora graminicola mycelium (arrows) in floral buds of pearl millet.B to F, Pathway of infection in systemically infected barley plants by Drechslera graminea.B, Diagrammatic Ls of part of developing spikelets from 80-day-old plant with mycelium innode, internode, and different parts of the floret, including base of the ovary. C, D, Parts ofnode and internode, respectively, showing intercellular mycelium (arrows). E, F, Parts of thebase of the ovary and the ovule showing intercellular mycelium (arrows). (Abbreviations: an,anther; fu, funiculus; my, mycelium; o, ovary; ov, ovule; ps, pollen sac; rin, rachis internode;rn, rachis node; sti, stigma.) (A, From Safeeulla, K.M. 1976. Biology and Control of theDowney Mildews of Pearl Millet. Downy Mildew Research Laboratory, Manasagangotri,Mysore University, India; B to F, Thakkar, R. 1988. Ph.D. thesis, University of Rajasthan,Jaipur, India.)
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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 49 and 50: 34 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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136 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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