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

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Seed Infection by Nematodes 239conditions. The developing pods are invaded after the fruiting pegs have penetratedthe soil. The nematodes enter the pod near the point of connection with the peg(Figure 8.5D). They invade the peg and feed on the parenchyma cells, which collapselater. The nematodes enter the exocarp, feed on the parenchyma cells, and migrateto the base of the mesocarp (Figure 8.5A, E). They remain confined to the sclerenchymatousmesocarp for quite some time, and its cells (in contact with nematodes)become discolored. As the mesocarp breaks down, the nematodes reach the endocarp.They enter the seed through the micropyle, invade the seed coat (Figure 8.5F) andembryo (Figure 8.5C), and lodge on the surface of the cotyledons. At maturity thetesta carry eggs and nematodes in the testa (Figure 8.5B, H). In the testa, nematodesmay also occur in vascular bundles (Figure 8.5G).Venter, McDonald, and van der Merwe (1995) have reported that Ditylenchusafricanus Wendt et al. (peanut pod nematode) is both seed- and soil-borne. Thenematodes survive in the testa and embryo of the seed and in the hull. Ditylenchusangustus has been found in dried seeds of rice, located mainly in the germ portion(Prasad and Varaprasad, 2002).8.2.5 APHELENCHOIDES BESSEYI CHRISTIE (WHITE TIP NEMATODEOF RICE)The disease was first described in the United States and Japan, but it is now knownin most of the rice-growing countries of the world (Franklin and Siddiqui, 1972;Franklin, 1982). The nematode is an ectoparasite that is carried beneath the hull inthe rice kernel. In India the disease has also been reported on Setaria italica, thefox tail millet (Lal and Mathur, 1988) and Panicum melacium (Gokte et al., 1990).Its other important host is strawberry in the United States and Australia and severalother flowering plants in Hawaii, the Philippines, and Japan (Franklin, 1982).Detailed histological observations are lacking. The infested seeds, upon reachingsoil, absorb moisture and the preadult nematodes emerge and move in the thin filmof water to reach different plant parts. They feed ectoparasitically on vegetativetissues, migrate to the growing panicle, puncture the inflorescence, reach the florets,and develop beneath the glumes. The nematode is amphimictic, and its densityincreases before anthesis. As the grain dries, second-stage larvae undergo anhydrobiosisand persist in the paddy kernel (Huang and Huang, 1972; Nandkumar et al.,1975). Nandkumar et al. (1975) have observed that in dry seed the nematodes remaincoiled up inside the palea and on the surface of the lodicules, which become paperyas the kernel matures.Aphelenchoides besseyi was detected beneath the glumes in anhydrobiotic statein P. miliaceum. The maximum number of nematodes obtained from a seed was 16,and the average number was 1.8 (Gokte et al., 1990).8.2.6 APHELENCHOIDES ARACHIDIS BOS (TESTA NEMATODE OFGROUNDNUT)The testa nematode of groundnut (A. arachidis) is a facultative endoparasite of roots,hypocotyl, pods, and testa (Bos, 1977). The nematode penetrates young roots and
240 Histopathology of Seed-Borne InfectionsmesnABCmesDEsccotscvbFGHFIGURE 8.5 Histopathology of peanut pod infected with D. destructor. A to C, Naturallyinfected. A, Ts through the mesocarp at the base of the young pod showing an opening createdby nematodes. B, Eggs and nematodes in testa of mature seed. C, Ls part of cotyledon showingnematodes and eggs. D to H, Artificially infected. D, Ts peg showing nematodes in parenchymatissue. E, Ts mesocarp at the base of a young pod showing discolored sclerenchymatissue and openings that developed following the presence of nematodes. F, G, Ts immaturepeanut seed showing nematodes in parenchyma and vascular bundle in seed coat. H, Ts matureseed showing nematodes in the parenchyma tissue of seed coat. (Abbreviations: cot, cotyledon;mes, mesocarp; n, nematode; sc, seed coat; vb, vascular bundle.) (From Jones, B.L. andDe Waele, D. 1990. J. Nematol. 22: 268–272. With permission.)
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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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TABLE 5.6Location of Mycelium of St
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Page 214 and 215: 7Seed Infection by VirusesViruses a
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Page 230 and 231: Seed Infection by Viruses 215ptowvv
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
Page 242: Seed Infection by Viruses 227Wolf,
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