Behavior of Alternaria brassicae and its mycoparasite Nectria inventa on intact and on excised leaves of rapeseed

1978 ◽  
Vol 56 (11) ◽  
pp. 1333-1340 ◽  
Author(s):  
A. Tsuneda ◽  
W. P. Skoropad
Keyword(s):  
Brassica Napus ◽  
Vegetative Growth ◽  
Primary Infection ◽  
Epidermal Cells ◽  
Alternaria Brassicae ◽  
Intact Leaves ◽  
Germ Tubes

On intact leaves of two cultivars (cv.) of rapeseed, Midas (Brassica napus) and Torch (B. campestris), conidia of Alternaria brassicae germinated at a rate of 12.1% and 19.5%, respectively, at 9 h after inoculation. They germinated usually by producing either germ tubes or secondary conidia. Penetration of leaves by A. brassicae was abundant at 24 h and occurred either with or without the formation of appressoria. Penetration of cv. Torch leaves by the fungus occurred either directly through epidermal cells or indirectly through stomata, while cv. Midas leaves were penetrated almost exclusively through stomata. Blackspot lesions developed within 48 h after inoculation.Conidia of Nectria inventa required at least 24 h to initiate germination and 4 days to parasitize A. brassicae on intact leaves. Therefore, N. inventa did not prevent primary infection of the leaves by A. brassicae. Instead, N. inventa suppressed the vegetative growth and sporulation of A. brassicae on excised rapeseed leaves.

Proteome-level changes in two Brassica napus lines exhibiting differential responses to the fungal pathogen Alternaria brassicae

Plant Science ◽  
2007 ◽  
Vol 172 (1) ◽  
pp. 95-110 ◽  
Author(s):  
Nidhi Sharma ◽  
Muhammad Hafizur Rahman ◽  
Stephen Strelkov ◽  
Mohan Thiagarajah ◽  
Vipan K. Bansal ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Fungal Pathogen ◽  
Alternaria Brassicae ◽  
Proteome Level ◽  
Differential Responses

The occurrence of functional non-chlorophyllous guard cells in Paphiopedilum spp.

1975 ◽  
Vol 53 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sherman D. Nelson ◽  
James M. Mayo
Keyword(s):  
Fluorescence Microscopy ◽  
Blue Light ◽  
Guard Cell ◽  
Direct Evidence ◽  
Light Response ◽  
Guard Cells ◽  
Epidermal Cells ◽  
Stomatal Response ◽  
Intact Leaves ◽  
Stomatal Functioning

Hypostomatous lady slipper orchids, Paphiopedilum spp., were found to have non-chlorophyllous epidermal cells, including guard cells. The lack of chlorophyll within the guard cells was demonstrated by fluorescence microscopy. A "normal" chlorophyllous mesophyll was present. The leaf resistances of intact leaves were about 5–10 s cm−1 in the light and were greater than 100 s cm−1 in the dark, indicating light opening and dark closure of the stomata. A CO2-dependent stomatal response (i.e., a tendency to close at elevated CO2 levels) was demonstrated, as was a CO2-independent light response (i.e., greater opening in blue light than in red). This provides direct evidence to support the idea that guard cell chlorophyll is not necessary for stomatal functioning.

scholarly journals Transfer of label from 3H-glucose in Digitaria eriantha leaves to the rust fungus Puccinia digitariae Pole Evans.

1985 ◽  
Vol 33 (8) ◽  
pp. 809-812 ◽  
Author(s):  
M E Rey ◽  
H M Garnett
Keyword(s):  
Primary Infection ◽  
Secondary Infection ◽  
Rust Fungus ◽  
Infection Process ◽  
Bremia Lactucae ◽  
Infection Structures ◽  
Obligate Parasites ◽  
Digitaria Eriantha ◽  
Germ Tubes

Digitaria eriantha pentzii was fed 3H-glucose prior to inoculation with uredospores of Puccinia digitariae Pole Evans. Twenty-one hours after inoculation, uptake of label from 3H-glucose by the primary infection structures of P. digitariae was demonstrated employing autoradiography. These results indicate that an exchange of nutrients between host and pathogen occurs very early on in the infection process, during the formation of the primary infection structures. Despite contrary reports that obligate parasites receive no nutrition before establishment of haustoria, this study supports the work of Andrews (Can J Bot 53:1103, 1975), who demonstrated uptake of 3H-glucose label from lettuce cotyledons into the primary and secondary infection vesicles, appressoria, and germ tubes of Bremia lactucae.

scholarly journals A note on phytotoxicity of homodestruxin B – a compound produced by Alternaria brassicae

2005 ◽  
Vol 74 (3) ◽  
pp. 157-160 ◽  
Author(s):  
P.S. Bains ◽  
J.P. Tewari ◽  
W.A. Ayer
Keyword(s):  
Brassica Napus ◽  
Host Plants ◽  
Alternaria Brassicae ◽  
Causal Organism

Homodestruxin B, a compound produced by Alternaria brassicae, the causal organism of the blackspot disease of rapeseed, is known to be phytotoxic to the leaves of Brassica napus. In this study we found that its phytotoxicity was comparable to that of destruxin B, another toxin produced by the pathogen when tested on B. napus. Homodestruxin B caused symptoms of different severities in leaves of various non-host plants. The results suggestthat homodestruxin B is a non-host-specific toxin.

The transition from germ tubes to vegetative growth in uredospores of Melampsora lini

1991 ◽  
Vol 69 (8) ◽  
pp. 1715-1718 ◽  
Author(s):  
R. Boasson ◽  
M. Shaw
Keyword(s):  
Vegetative Growth ◽  
Mycelial Growth ◽  
Rust Fungus ◽  
Axenic Culture ◽  
Single Spore ◽  
Naked Eye ◽  
Melampsora Lini ◽  
Rate Of Increase ◽  
Germ Tubes ◽  
Spore Densities

The transition from uredospore germ tubes to vegetative hyphae marks the initiation of mycelial colonies of Melampsora lini growing in axenic culture. It is promoted by heat shock (31 °C for 2 h) and is arbitrarily defined as having occurred when mitotic divisions of the two original uredospore nuclei have produced more than four nuclei. The percentage of germinating spores in which it occurs (percentage initiation) does not increase beyond 48 h after seeding and is higher (about 9 vs. 5%) at a low (18 spores/mm2) than at a higher (90 spores/mm2) inoculum density. The number of nuclei in a mycelial colony arising from a single uredospore increases exponentially with a mean doubling time of 2.40 days. Neither the percentage initiation nor the rate of increase in number of nuclei (= mycelial growth) are affected by the proximity of neighbouring spores at spore densities of the order of 18 spores/mm2. Approximately 10% of the initiated colonies exhibit a growth rate that renders them visible to the naked eye after 5 weeks. Key words: rust fungus, axenic culture, vegetative growth, single spore colonies.

Conidial morphology, host colonization, and development of shot hole of almond caused by Wilsonomyces carpophilus

1995 ◽  
Vol 73 (3) ◽  
pp. 432-444 ◽  
Author(s):  
J. E. Adaskaveg
Keyword(s):  
Middle Lamella ◽  
Leaf Tissue ◽  
Outer Wall ◽  
Wall Layer ◽  
Epidermal Cells ◽  
Host Tissue ◽  
Tissue Response ◽  
Abscission Layer ◽  
Infection Period ◽  
Germ Tubes

Morphology and ultrastructure of shot hole disease of almond infected by conidia of Wilsonomyces carpophilus were examined using light, scanning, and transmission electron microscopy. The multicelled conidia of the fungus were thick-walled and darkly pigmented. The conidial wall was multilayered and mainly consisted of an electron-dense, outer-wall layer and an electron-translucent, inner-wall layer. Septa of conidia were also multilayered. An electron-translucent zone separated the electron-dense, septa-wall layers of adjacent cells, and this zone extended to the inside of the outer-wall layer of a conidium. Conidia lacked true septa (distoseptate) and germinated by rupturing the outer-wall layers. Germination hyphae penetrated indirectly through stomata or directly through the cuticle into leaf tissue from appressoria that were produced terminally or on lateral branches of germ tubes. An extracellular mucilaginous matrix was commonly observed around hyphae and germ tubes in contact with leaf surfaces. Within leaf tissue, hyphae ramified throughout intercellular spaces and degraded cell walls of epidermal cells apparently without cuticle degradation. Diseased host tissue was tan brown and collapsed; ultrastracturally, diseased leaf cells were reduced in size, nonvacuolated, and had disrupted chloroplasts. A healthy host tissue response, adjacent to an infection site on leaves of potted plants, was the formation of a wound periderm. Within 10–14 days after an infection period (16 h of wetness), the periderm became a lignified–suberized barrier at 15 °C or a suberized abscission layer at 22 °C based on the histological stains Safranin O, Sudan III, and Sudan Black. At 15 °C, no abscission occurred and meristematic cells remained isodiametric but their walls became suberized and lignified, whereas cells adjacent to diseased tissue became lignified. At 22 °C, abscission occurred as cells adjacent to diseased tissue became vacuolated, enlarged, and suberized. Subsequently, the epidermis ruptured and the enlarged cells separated along the middle lamella to form an abscission layer. Hyphal growth was limited to the boundaries of the walled-off diseased tissue. Under favorable environmental conditions, hyphae replaced host epidermal cells and aggregated above the palisade layer to form pulvinate sporodochia. Sporodochia consisted of hyphae, numerous sympodially developing conidiogenous cells, and conidia that ruptured the host cuticle. Key words: fungal morphology, fungal foliar diseases, wound periderm, host–parasite interactions.

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