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

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Location of Fungal Hyphae in Seeds 109scendembABCFIGURE 5.4 A, B, Phytophthora parasitica f. sp. sesami in sesame seed. A, Transversesection of seed having oospores and hyphae in seed coat, and hyphae in endosperm andembryo. B, Part from A magnified to show intercellular mycelium in endosperm. C, Ts partof soybean seed coat with hyphae of Peronospora manshurica in various layers (arrows) andoospores and mycelium on seed surface. (Abbreviations: emb, embryo; end, endosperm;sc, seed coat.) (A, B, From Dubey, A.K. 2000. Ph.D. thesis, University of Rajastan, Jaipur,India; C, From Roongruangsree, U-Tai et al. 1988. J. Phytopathol. 123, 1326–1328. Withpermission).
110 Histopathology of Seed-Borne InfectionsNeergaard (1979) reported the occurrence of Phytophthora cinnamomi myceliumin the embryo of avocado pear seed. Kumi et al. (1996) also observed thatcacao seeds from symptomatic (black) and asymptomatic pods from infected treesof Theobroma cacao yielded Phytophthora from more than 90% of embryos, butthe recovery was only 4% from seed coat. Such seeds either failed to germinate orproduced seedlings that usually died soon after germination or, if they survived,were stunted and developed leaf spots.5.5.1.2 PeronosporaLeach (1931) found mycelium and oospores of Peronospora farinosa (Peronosporaschachtii) in the seed coat of sugar beet and Melhus (1931) found mycelium andoospores of P. viciae in the seed coat of pea. The presence of oospore crust onsoybean seeds, first described by Johnson and Lefebvre (1942), is well known, Suchseeds are produced in infected pods (Hildebrand and Koch, 1951; Mckenzie andWyllie, 1971) and cause systemic infection in seedlings (Lehman, 1953; Zad, 1989).Roongruangsree, Olson, and Lange (1988) found that seeds encrusted by P. manshurica,contain, in addition to the oospores, thick- and thin-walled mycelium onthe seed surface. Only thin-walled mycelium occurred in the seed coat betweenpalisade cells, hourglass cells, and thin-walled parenchyma layers (Figure 5.4 C).The oospores, thick-walled mycelium on seed surface and mycelium in seed coat,retain viability. Hildebrand and Koch (1951) also observed fragments of myceliumof P. manshurica within the palisade and hourglass cells, but considered them to besenescent.Peronospora ducomati, the causal agent of downy mildew of buckwheat(Fagopyrum esculentum), is also internally seed-borne (Zimmer, McKeen, andCampbell, 1992). The commercial seed is in fact an indehiscent, one-seeded fruit,the achene. According to Zimmer, McKeen, and Campbell (1992), oospores ofP. ducomati occur in the remnant of persistent calyx on the inside of the seed coat(probably the pericarp) and in the spermoderm layer (the seed coat). The seed-borneoospores constitute the primary inoculum that causes systemic invasion of the seedlingsat the time of germination.5.5.1.3 PlasmoparaPlasmopara halstedii (P. helianthii) is an obligate parasite that causes downy mildewof sunflower. Seeds (cypsils) with severe infection contain mycelium in all partsincluding the embryo (Novotelnova, 1963; Cohen and Sackston, 1974). Doken(1989) observed hyphae of P. halstedii in the pericarp and testa (seed coat) of seedsfrom systemically infected sunflower plants. No infection was seen in the embryoin these seeds. The infection entered the ovary from the receptacle, and the fungalcolonization was especially dense in the hilum region (the point of fruit separation).5.5.1.4 Sclerospora, Peronosclerospora, and SclerophthoraIn 1920, Weston was the first to show that the mycelium of Sclerospora is internallyseed-borne, followed by Arya and Sharma in 1962. Weston (1920) reported the
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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
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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160 Histopathology of Seed-Borne In
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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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