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

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Location of Fungal Hyphae in Seeds 121stymyperscalendlbmydesctcolptimysaprcolrAFIGURE 5.11 Location of loose smut mycelium in seed and young seedling of barley.A, Diagrammatic representation (Ls) of the distribution of mycelium of Ustilago nuda in aninfected barley grain. B, Diagrammatic representation of U. nuda mycelium in crown nodeof 5-week-old seedling. (Abbreviations: al, aleurone layer; colp, coleoptile; colr, coleorhiza;de, developing ear; end, endosperm; lb, leaf bases; my, mycelium; per, pericarp; pr, primaryroot; sa, shoot apex; sc, seed coat; sct, scutellum; sty, stylar tissue; ti, tillers.) (Redrawn fromMalik, M.M.S. and Batts, C.C.V. 1960a. Trans. Br. Mycol. Soc. 43: 112–125 and Malik,M.M.S. and Batts, C.C.V. 1960b. Trans. Br. Mycol. Soc. 43: 126–131.)of infection and location of mycelium of U. tritici and U. nuda in wheat and barleygrains (Ruttle, 1934; Vanderwalle, 1942; Simmonds, 1946; Batts, 1955; Pedersen,1956; Malik and Batts, 1960a; Loiselle and Shands, 1960; Kozera, 1968; Shinohara,1972). Batts (1955), working with artificially as well as naturally infected wheatgrains, and Malik and Batts (1960a), working with barley grains, have shown thatentry and location of U. tritici and U. nuda mycelium in wheat and barley grainsare similar. In grains obtained from plants inoculated at the time of anthesis, themycelium occurs in the pericarp, testa, aleurone layer, other layers of endosperm,and embryo (Figure 5.11A). It is mainly intracellular in the pericarp and testa, andusually intercellular in the aleurone layer, the other layers of endosperm, and theembryo. The mycelium has not been found in the radicle. In cases where the infectionB
122 Histopathology of Seed-Borne Infectionsoccurs just before the ripening of the grains, hyphae are confined to the endosperm,especially at the base (Pedersen, 1956). Ohms and Bever (1956) also observed thehighest percentage of infected embryos with a large amount of hyphae when inoculationswere made at anthesis in winter wheat. Inoculation made after anthesisshowed a decreased percentage of infected embryos with a small amount of hyphae.The embryo count method is commonly used in routine seed health testing forthe detection of loose smut mycelium in wheat seed lots. In extracted embryos, themycelium takes trypan blue stain, but the older mycelium is brown and does notstain. The smut mycelium is broad and branched (Khanzada et al., 1980; Mathurand Cunfer, 1993).Loiselle and Shands (1960) compared the location of U. nuda in grains ofresistant and susceptible barley cultivars. They found that in grains of resistant plantsmycelium was confined to the chalaza and the parenchyma associated with thevascular bundle while in grains of susceptible cultivars, it occurred in the integument(seed coat and pericarp), aleurone, endosperm, and embryo. Batts and Jeater (1958)and Popp (1959) found three different reactions when resistant and susceptiblecultivars were artificially inoculated by different races of U. tritici. Mycelium spreadin all tissues of the embryo of susceptible cultivars. The scutellum and plumular budwere regularly infected, but the coleoptile, epiblast, radicle, coloerhiza, and suspensorwere less frequently infected. In resistant varieties, only the scutellum wasconsistently infected and the plumule bud had no infection. Other structures wereless frequently infected. All parts of the embryo were free of infection in totallyresistant or immune varieties. Popp (1959) further demonstrated that only infectionof plumule bud is directly correlated with smut infection in plants grown frominfected seed (Table 5.4). Based on the above criteria, a reasonably accurate predictionof percentage of smut infection in field plants can be made. Based on recordingsof scutellum infection, however, Khanzada et al. (1980) found that the laboratorycounts of the embryo infection in wheat seed closely correlated to the number ofsmutted plants in the field.Batts and Jeater (1958) and Malik and Batts (1960b) determined the developmentof the fungus in infected germinating seed, seedling, and plant in susceptible cultivarsof wheat and barley, respectively. The mycelium becomes active at the time of seedgermination and is carried upward by the elongation of the plumule (epicotyl). Themycelium spreads in the crown node in which the development of all parts of theadult plant (nodes, internodes, and ears of each tiller with its leaf sheath) takes place.The smut mycelium permeates the whole structure including the ears (Figure 5.11B).During further development, stems elongate and the mycelium already present inthe ears is carried up. By the time the ears emerge out of the leaf sheath, all of itsparts except the rachis are completely replaced by spores.Wallen (1964) has reported that the cultivar Keystone barley in Canada isextremely embryo susceptible but mature plant resistant. The embryal infection isnever transferred to the plant.5.5.3.1.2 Type 2 Disease CycleCommon bunt or stinking smut is caused by two closely related pathogens, T. tritici(T. caries) and T. laevis (T. foetida). Bunt balls are seed- as well as soil-borne. 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
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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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Page 90 and 91: Structure of Seeds 75Baker, D.M. an
Page 92 and 93: Structure of Seeds 77Maheshwari Dev
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172 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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