Location <strong>of</strong> Fungal Hyphae in <strong>Seed</strong>s 131TABLE 5.5 (CONTINUED)Location <strong>of</strong> Fungi Belonging to Deuteromycetes in <strong>Seed</strong>s <strong>of</strong> Crop PlantsFungusHost<strong>Seed</strong> and FruitPart(s)Important ReferencesCoelomycetes (continued)Diplodia zeae Zea mays Pericarp, endosperm,embryoHeald et al., 1909;Miller, 1952Phoma lingam Brassica oleracea <strong>Seed</strong> coat Jacobsen and Williams,1971P. sorghina Sorghum vulgare Pericarp, endosperm, Rastogi et al., 1991embryoPhomopsis heveae Hevea brasiliensis <strong>Seed</strong> coat (tegmen) Varma et al., 1991perisperm,endosperm, embryoPhomopsis sp. Glycine max <strong>Seed</strong> coat, hilar tissue,embryoIlyas et al., 1975; Singhand Sinclair, 1986Septoria glycines Glycine max <strong>Seed</strong> coat Sinclair and Backman,1989S. linicola Linum usitatissimum <strong>Seed</strong> coat Lafferty, 1921Stagnospora nodorum Triticum aestivum Pericarp, seed coat, Agarwal et al., 1985endosperm, embryoStagnospora sp. Hevea brasiliensis <strong>Seed</strong> coat (tegmen);perisperm,endosperm, embryoVarma et al., 1991RhizoctoniabataticolaVigna spp. <strong>Seed</strong> coat, embryo Sinha and Khare, 1977;Varma et al., 1992a,bPhaseolus vulgaris <strong>Seed</strong> coat, embryo Agarwal and Jain, 1978Sesamum indicum <strong>Seed</strong> coat, endosperm, Singh and Singh, 1979embryoCrotolaria juncea <strong>Seed</strong> coat, embryo Basu Choudhary and Pal,1982Helianthus annuusGlycine maxPericarp, endosperm,embryo-cotyledons(rare)<strong>Seed</strong> coat, endosperm,embryoRaut, 1983; Godika, 1996;Godika et al., 1999Kunwar et al., 1986b;Mathur, 1992Cajanus cajan <strong>Seed</strong> coat, embryo Sharma, 1996Cyamopsis<strong>Seed</strong> coat, endosperm, Bhatia et al., 1998tetragonoloba embryoAbelmoschus<strong>Seed</strong> coat, embryo Agarwal and Singh, 2000esculentusR. solani Capsicum annuum <strong>Seed</strong> coat, endosperm Baker, 1947;Chitkara et al., 1986b
132 <strong>Histopathology</strong> <strong>of</strong> <strong>Seed</strong>-<strong>Borne</strong> <strong>Infections</strong>Alternaria infection, established as dormant mycelium, is reported in seed coatfor Alternaria brassicae in Brassica (Chupp, 1935), Alternaria brassicicola inBrassica (Boek, 1952; Domsch, 1957), and Alternaria longipes in tobacco (Heursel,1961), and in the pericarp <strong>of</strong> carrot for Alternaria dauci and Alternaria radicina(Soteros, 1979; Netzer and Kenneth, 1969). Atkinson (1950) alone recorded Alternariaraphani in the seed coat and embryo <strong>of</strong> radish.Dormant mycelium <strong>of</strong> Alternaria alternata (Alternaria tenuis) occurs in the seedcoat and pericarp in asymptomatic and weakly symptomatic seeds. Moderately toheavily infected seeds carry fungal mycelium in all parts — the seed coat or pericarpand seed coat (one-seeded dry fruits), endosperm, and embryo in the case <strong>of</strong> Capsicum,Glycine, Brassica, Eruca, Helianthus, and Cumin (Table 5.5). In weaklyinfected seeds <strong>of</strong> soybean inter- and intracellular hyphae occur in all the layers <strong>of</strong>the seed coat. Rarely do hyphae traverse the cells <strong>of</strong> endosperm and peripheral layers<strong>of</strong> the cotyledon. Moderately and heavily infected seeds carry a thick mat <strong>of</strong> hyphaein the region <strong>of</strong> seed coat parenchyma and endosperm; the two zones are indistinct.Hyphae also occur in all the parts <strong>of</strong> the embryo. In the hilar region, hyphae areseen outside as well as inside the hilium. When the hyphae are internal, they occurin the parenchyma and the tracheid bar (Kunwar, Manandhar, and Sinclair, 1986a).In Hordeum vulgare the husk, persistent lodicules, pericarp, and endosperm areinfected (Thakkar, 1988). The mycelium usually occurs in layers <strong>of</strong> pericarp andtesta outside the thick cuticle <strong>of</strong> the endosperm in sunflower seeds. Rarely in heavilyinfected seeds, the mycelium penetrates the cuticle and invades the endosperm andembryo (Singh, Mathur, and Neergaard, 1977; Godika, Agarwal, and Singh, 1999).In Alternaria sesamicola, the cause <strong>of</strong> sesame blight, the mycelium readilyspreads in s<strong>of</strong>t parenchymatous layers <strong>of</strong> the seed coat. The epidermal cells, whichhave calcium oxalate crystals, remain free <strong>of</strong> infection in weak and moderatelyinfected seeds (Figure 5.14A, B). In severely infected seeds, abundant myceliumoccurs in all parts <strong>of</strong> the seed showing host cell disintegration (Figure 5.14C, D).Conidia formation occurs in spaces in the seed and also on the seed surface. Suchseeds were probably infected early during development or had prolonged humidenvironments after being infected.In A. brassicicola, the cause <strong>of</strong> leaf spot and blight <strong>of</strong> crucifers, infected seedsare asymptomatic and symptomatic in Brassica juncea, B. campestris, and Erucasativa. In asymptomatic infected and weakly infected seeds, the hyphae are confinedto the seed coat. However, in moderate and heavily infected seeds (bold discoloredand shriveled discolored), the hyphae occur in the seed coat, endosperm, and embryo.The infection is maximum (100%) in the seed coat and gradually declines in theendosperm and embryo (Sharma, 1989; Sharma, 1992). Among the Brassica spp.,the severity <strong>of</strong> seed infection was greater in mustard (B. juncea) than in rapeseed(B. campestris). Knox-Davies (1979) has found that in cabbage seeds naturallyinfected by A. brassicicola, the testa is usually colonized in the hilum area.5.5.4.1.2 CurvulariaCurvularia lunata is a common seed-borne fungus, recorded in seeds <strong>of</strong> field cropsall over the world (Richardson, 1990). It is one <strong>of</strong> the fungi that caused grain molddisease in sorghum (Rastogi, Singh, and Singh, 1990). The affected seeds are
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