Genetics and cytology of age-related resistance in North American cultivars of cowpea (Vigna unguiculata) to the cowpea rust fungus (Uromyces vignae)

1994 ◽  
Vol 72 (5) ◽  
pp. 575-581 ◽  
Author(s):  
Michèle C. Heath
Keyword(s):  
Resistance Gene ◽  
Rust Fungus ◽  
Leaf Age ◽  
Fungal Growth ◽  
Individual Plant ◽  
Infection Site ◽  
Age Related ◽  
Race 1 ◽  
Uromyces Vignae ◽  
Site Types

Increasing leaf age was accompanied by increases in resistance in three incompatible cowpea cultivars inoculated with race 1 of Uromyces vignae and in three of four cultivars that had previously been considered susceptible to race N2. Selected crosses between cultivars suggested that resistance to race 1 was controlled by the same genes in young and old leaves, and they indicated that age-related resistance to race N2 was primarily controlled by a single, and different, gene in each cultivar. All examples of resistance were expressed cytologically as a range of infection site types in a single leaf, the frequency distribution of which was affected by the type of resistance gene, gene heterozygosity, and leaf age. These frequency distributions shifted with increasing leaf age towards infection sites with less fungal growth and more rapid plant cell necrosis, often abolishing the cytological differences between cultivars and genotypes seen in younger plants. The data suggest that each rust resistance gene in cowpea can generate a range of infection site types, and that fungal growth and plant responses at each infection site are governed by a combination of the number and type of resistance genes in the plant, the race of the fungus, and age-affected features of individual plant cells. Key words: cowpea, rust fungi, age-related resistance.

Cytological studies of the hypersensitive death of cowpea epidermal cells induced by basidiospore-derived infection by the cowpea rust fungus

1991 ◽  
Vol 69 (6) ◽  
pp. 1199-1206 ◽  
Author(s):  
C. Y. Chen ◽  
Michele C. Heath
Keyword(s):  
Hypersensitive Response ◽  
Cell Walls ◽  
Cytoplasmic Streaming ◽  
Rust Fungus ◽  
Fungal Growth ◽  
Inhibitory Effect ◽  
Epidermal Cells ◽  
Plant Cell Walls ◽  
Powdery Mildew Fungus ◽  
Uromyces Vignae

The cytological responses to the monokaryotic primary hyphae of the cowpea rust fungus (Uromyces vignae Barcl.) were observed in vein epidermal cells of a resistant and a susceptible cowpea cultivar. Unlike the previously examined response to haustoria of a nonpathogenic powdery mildew fungus, plant cell walls did not become autofluorescent in response to fungal penetration, and the primary hypha only rarely became encased. Following fungal penetration, the response of invaded cells of the resistant, intact plant could be divided into the following stages: (I) cytoplasmic streaming normal; (II) cytoplasmic streaming slow or stopped, Brownian motion of particles visible in the vacuole, granulated cytoplasm aggregated along the cell walls, some host nuclei disappeared; and (III) protoplast collapsed. Epidermal tissue of the resistant cultivar did not exhibit stages II–III when detached and mounted in water 12 h after inoculation and examined 9 h later. The frequency of stage III increased when the tissue was mounted in CaCl2, Ca(NO3)2, and KNO3, but only in a kinetin solution did it approximate that in attached tissue. Although kinetin inhibited fungal growth in both the resistant and the susceptible cultivar, the hypersensitive response occurred only in the former, suggesting that kinetin affects the hypersensitive response directly rather than through its inhibitory effect on the fungus. Key words: cowpea, Vigna unguiculata, cowpea rust fungus, Uromyces vignae (Barcl.), hypersensitivity.

scholarly journals DISTRIBUTION AND RACE COMPOSITION OF DOWNY MILDEW (Plasmopara halstedii (Farl.) Berl. and de Toni) IN BULGARIA / EXTENSION Y RAZAS DEL MILDIU (Plasmopara halstedii (Farl.) Berl. y de Toni) EN BULGARIA / ÉTENDUE ET RACES DE LA ROUILLE (Plasmopara halstedii (Farl.) Berl. and de Toni) EN BULGARIE

Helia ◽  
2000 ◽  
Vol 23 (33) ◽  
pp. 25-32
Author(s):  
P.S. Shindrova
Keyword(s):  
Downy Mildew ◽  
Resistance Gene ◽  
The Other ◽  
Plasmopara Halstedii ◽  
North West ◽  
North East ◽  
Race 1 ◽  
Race 2 ◽  
Production Areas ◽  
Number Of Authors

SUMMARY Downy mildew caused by the fungus Plasmopara halstedii is the main disease on sunflower in Bulgaria. In recent years a number of authors have reported the occurrence of new more virulent races of the pathogen. According to other authors these races demonstrate resistance to the fungicides used up to now. This fact is rather alarming and imposes the necessity of annual researches with the aim of following the changes in the downy mildew race variability. In the period 1995-1997 downy mildew isolates were collected from the following locations: Bourgas, Boyanovo, Karnobat, Ognyanovo, Selanovtsi, Kroushari, Lovech, Koubrat, Brashlyan, Sitovo, Tervel, Targovishte, IWS “Dobroudja” and Dobrich. The samples were assessed for virulence on a set of sunflower differential - lines under greenhouse conditions. The obtained results do not reveal a great race variability of downy mildew population in Bulgaria. In the period of study two races of the pathogen were identified: race 1 which infects the differential lines without genes for resistance to the pathogen. It is distributed in all sunflower production areas of the country. The other one is race 2. It is of limited distribution and has been registered in individual fields of north-east and north-west Bulgaria. It attacks the differential lines carrying the resistance gene Pl-1.

Leaf age-related changes in respiratory pathways are dependent on complex I activity in Nicotiana sylvestris

2007 ◽  
Vol 129 (1) ◽  
pp. 152-162 ◽  
Author(s):  
Pierrick Priault ◽  
Guillaume Vidal ◽  
Rosine De Paepe ◽  
Miquel Ribas-Carbo
Keyword(s):  
Complex I ◽  
Leaf Age ◽  
Nicotiana Sylvestris ◽  
Age Related ◽  
Complex I Activity ◽  
Age Related Changes

Changes in the plant endomembrane system associated with callose synthesis during the interaction between cowpea (Vigna unguiculata) and the cowpea rust fungus (Uromyces vignae)

1995 ◽  
Vol 73 (11) ◽  
pp. 1731-1738 ◽  
Author(s):  
Dubravka Škalamera ◽  
Michèle C. Heath
Keyword(s):  
Endoplasmic Reticulum ◽  
Vigna Unguiculata ◽  
De Novo ◽  
Rust Fungus ◽  
Leaf Tissue ◽  
Resistant Cultivar ◽  
Callose Deposition ◽  
Golgi Membranes ◽  
Rough Er ◽  
Uromyces Vignae

Electron microscopy and stereological analysis of cowpea (Vigna unguiculata) leaf tissue infected with the cowpea rust fungus (Uromyces vignae) revealed an increase in surface of plant endomembranes that was associated with callose synthesis or the presence of fungal haustoria. In the resistant cultivar in which the haustorium commonly becomes encased, an increase in surface of smooth membranes was observed in cytoplasmic regions adjacent to developing encasements compared with the regions away from the fungus or with any region in infected or uninfected callose nonsynthesizing cells. Cytoplasmic regions adjacent to the haustorium in callose nonsynthesizing cells had an increase in rough endoplasmic reticulum (ER). This increase was greater in a susceptible cultivar than in the resistant cultivar that was treated with tunicamycin to inhibit callose synthesis. In the latter situation, the lack of callose encasement allowed the haustorial neckband to form, but other ultrastructural signs of incompatibility remained, such as the presence of electron-opaque material associated with the extrahaustorial membrane. No differences between cultivars or treatments were observed in Golgi membranes. Our observations suggest that both callose synthesis and fungal presence are associated with de novo synthesis of membranes; callose deposition may require an increase in smooth membranes of uncertain origin, whereas the establishment of a haustorium may be dependent on increased synthesis of rough ER. Key words: callose, endoplasmic reticulum, resistance, stereology, tunicamycin.

scholarly journals An Investigation into the Involvement of Defense Signaling Pathways in Components of the Nonhost Resistance of Arabidopsis thaliana to Rust Fungi Also Reveals a Model System for Studying Rust Fungal Compatibility

2003 ◽  
Vol 16 (5) ◽  
pp. 398-404 ◽  
Author(s):  
Denny G. Mellersh ◽  
Michèle C. Heath
Keyword(s):  
Arabidopsis Thaliana ◽  
Rust Fungus ◽  
Fungal Growth ◽  
Rust Fungi ◽  
Nonhost Resistance ◽  
Wild Type ◽  
Pr Genes ◽  
Hypersensitive Cell Death ◽  
Defense Signaling ◽  
Infection Hypha

Seventeen accessions of Arabidopsis thaliana inoculated with the cowpea rust fungus Uromyces vignae exhibited a variety of expressions of nonhost resistance, although infection hypha growth typically ceased before the formation of the first haustorium, except in Ws-0. Compared with wild-type plants, there was no increased fungal growth in ndr1 or eds1 mutants defective in two of the signal cascades regulated by the major class of Arabidopsis host resistance genes. However, in the Col-0 background, infection hyphae of U. vignae and two other rust fungi were longer in sid2 mutants defective in an enzyme that synthesizes salicylic acid (SA), in npr1 mutants deficient in a regulator of the expression of SA-dependent pathogenesis related (PR) genes, and in NahG plants containing a bacterial salicylate hydroxylase. Infection hyphae of U. vignae and U. appendiculatus but not of Puccinia helianthi were also longer in jar1 mutants, which are defective in the jasmonic acid defense signaling pathway. Nevertheless, haustorium formation increased only for the Uromyces spp. and only in sid2 mutants or NahG plants. Rather than the hypersensitive cell death that usually accompanies haustorium formation in nonhost plants, Arabidopsis typically encased haustoria in calloselike material. Growing fungal colonies of both Uromyces spp., indicative of a successful biotrophic relationship between plant and fungus, formed in NahG plants, but only U. vignae formed growing colonies in the sid2 mutants and cycloheximide-treated wild-type plants. Growing colonies did not develop in NahG tobacco or tomato plants. These data suggest that nonhost resistance of Arabidopsis to rust fungi primarily involves the restriction of infection hypha growth as a result of defense gene expression. However, there is a subsequent involvement of SA but not SA-dependent PR genes in preventing the Uromyces spp. from forming the first haustorium and establishing a sufficient biotrophic relationship to support further fungal growth. The U. vignae-Arabidopsis combination could allow the application of the powerful genetic capabilities of this model plant to the study of compatibility as well as nonhost resistance to rust fungi.

Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. IV. Effect of preinoculation with the bean rust fungus on growth of parasitic fungi nonpathogenic on beans

1991 ◽  
Vol 69 (8) ◽  
pp. 1642-1646 ◽  
Author(s):  
Myriam R. Fernandez ◽  
Michèle C. Heath
Keyword(s):  
Rust Fungus ◽  
Fungal Growth ◽  
Hyphal Growth ◽  
French Bean ◽  
Bean Rust ◽  
Protein Synthesis Inhibitors ◽  
Rust Infection ◽  
Parasitic Fungi ◽  
Wall Appositions ◽  
Bean Leaves

Bean leaves inoculated 24 h previously with the bean rust fungus were inoculated with spores of Cochliobolus heterostrophus, Stemphylium sarcinaeforme, Stemphylium botryosum, or Cladosporium fulvum. For all species except C. fulvum, hyphal growth resulting from stomatal penetrations was greater than that in leaves that were not rust-infected but did not continue for more than about 24 h. The incidence of direct penetrations for these three fungi also was increased by prior rust infection, and the incidence of epidermal wall appositions was reduced. Growth of C. fulvum in rust-infected leaves only exceeded that in control leaves when spores were injected into the intercellular spaces of the mesophyll tissue. Rust infection either had little effect on the incidence of cell death, normally induced by all of the tested fungi except C. fulvum, or it enhanced this response in association with greater fungal growth. From this and previous studies, it seems that successful rust infection increases the growth of a wider array of fungi nonparasitic to beans than treatments with growth regulators or intercellular washing fluids from rusted tissue. Its effect is most closely mimicked by preinoculation treatments with heat or protein synthesis inhibitors, but it does not induce indiscriminate susceptibility. Its effect may, in part, be due to the suppression of defenses involving wall modifications. Key words: Uromyces appendiculatus, induced susceptibility, nonhost resistance.

RESPONSE OF NEAR-ISOGENIC PEA CULTIVARS TO INFECTION BY Fusarium oxysporum f. sp. pisi RACES 1 AND 5

1989 ◽  
Vol 69 (4) ◽  
pp. 1335-1346 ◽  
Author(s):  
M. CHARCHAR ◽  
J. M. KRAFT
Keyword(s):  
Fusarium Oxysporum ◽  
Lateral Roots ◽  
Dominant Gene ◽  
Fungal Growth ◽  
Resistance Response ◽  
Resistant Cultivars ◽  
Tap Root ◽  
Race 1 ◽  
Xylem Elements ◽  
Root Apices

Near-isogenic pea cultivars, differing by a single dominant gene for resistance (R) or susceptibility (S) to Fusarium oxysporum f. sp. pisi race 1 (’M410’-S, ’Vantage’-R) or race 5 (’Sundance’-S, ’Sundance II’-R), were evaluated for their response to infection. The response of resistant cultivars to each race was similar. Colonies of both races were isolated in higher numbers from tap and lateral root apices of susceptible as compared with resistant cultivars. Internal tap root and hypocotyl invasion occurred in all cultivars tested. However, lateral roots and stems of resistant cultivars were not infected as compared with susceptible lines. Surface colonization of tap and lateral roots of the resistant cultivars was significantly less than with the susceptible cultivars. Scanning electron microscopy revealed that gel-like material completely sealed off xylem elements in lateral roots, epicotyls, and aboveground stems of resistant cultivars. In contrast, intense mycelial invasion, without the formation of gels, occurred in susceptible cultivars. Conidial germination and germ-tube growth of both race 1 and race 5 were stimulated by xylem fluids from the susceptible, but not from the resistant cultivars. A resistance response based on physical containment and reduced fungal growth was evident.Key words: Fusarium wilt, host response, Pisum sativum

RAPD markers for a sunflower rust resistance gene

1996 ◽  
Vol 47 (3) ◽  
pp. 395 ◽  
Author(s):  
WR Lawson ◽  
KC Goulter ◽  
RJ Henry ◽  
GA Kong ◽  
JK Kochman
Keyword(s):  
Resistance Gene ◽  
Rust Resistance ◽  
Durable Resistance ◽  
Dominant Gene ◽  
Rust Resistance Gene ◽  
Breeding Programs ◽  
Resistant Parent ◽  
F2 Population ◽  
Race 1 ◽  
Selection For

An F2 population of sunflower (Helianthus annuus L.) was tested for segregation of a gene conferring resistance to sunflower rust (Puccznia helzanthi) Australian Race 0 (North American Race 1). The resistant parent, RHA279, of this cross was thought to possess a single dominant resistance gene to this race. Genetic analysis confirmed that this population was segregating for a single dominant gene, the R1 gene, for resistance to this race of the pathogen. Using bulked segregant and RAPD analyses, two markers were identified which co-segregated with the rust resistance gene in the F2 population. These markers, designated OT06959 and 01\/112850, are linked to the rust resistance gene at a distance of 4.5 cM and 26 cM, respectively, with the markers situated one either side of the gene. The availability of markers closely linked to this gene will greatly enhance selection for the gene in future breeding programs, and especially assist efforts to pyramid the gene with other rust resistance genes to produce sunflower varieties with more durable resistance to rust.

scholarly journals Occurrence of Podosphaera xanthii Race 2 on Cucumis melo in Brazil

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1161-1161 ◽  
Author(s):  
R. F. Kobori ◽  
O. Suzuki ◽  
R. Wierzbicki ◽  
P. T. Della Vecchia ◽  
L. E. A. Camargo
Keyword(s):  
Cucumis Melo ◽  
Fungal Growth ◽  
Sao Paulo ◽  
Podosphaera Xanthii ◽  
São Paulo ◽  
Erysiphe Cichoracearum ◽  
Summer Squash ◽  
Golovinomyces Cichoracearum ◽  
Race 1 ◽  
Race 2

Powdery mildew is an important disease of melons (Cucumis melo L.) cultivated in greenhouses in Brazil. Currently, there are 5 races of Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) and 2 races of Golovinomyces cichoracearum (formerly known as Erysiphe cichoracearum) described on melons worldwide, but only race 1 of P. xanthii has been reported in Brazil (1). However, typical whitish powdery fungal growth was observed on an experimental hybrid yellow melon resistant to race 1 of P. xanthii during the summer of 2000 in a greenhouse in Bragança Paulista, State of São Paulo. Conidia collected from diseased leaves were spread onto 0.5% water agar medium and maintained at 22°C for 24 h with 12 h of light and 12 h of darkness. Most of the germinated conidia displayed fibrosin inclusion bodies when observed in a solution of 3% potassium hydroxide (KOH), and approximately 1 of 50 also displayed forked germ tubes. These features allowed us to identify P. xanthii as the causal agent. Conidia raised on the susceptible yellow melon ‘Amarelo CAC’ were used to inoculate cotyledons of the differential melon lines (2) ‘Hale's Best Jumbo’ (susceptible to races 1, 2, and 3 of P. xanthii), ‘PMR-45’ (resistant to race 1 and susceptible to races 2 and 3), and ‘PMR-6’ (resistant to races 1 and 2 and susceptible to race 3). Inoculations were performed on 10 plants of each differential line and replicated four times. The presence or absence of symptoms was evaluated 18 days after inoculation. ‘Hale's Best Jumbo’ and ‘PMR-45’ were rated as susceptible while ‘PMR-6’ was rated as resistant, thus indicating the presence of race 2 of P. xanthii in Brazil. During field surveys from 2001 to 2003, this race was found on squash (Cucurbita moschata), summer squash (C. pepo), and melons in São Paulo. References: (1) F. J. B. Reifschneider et al. Plant Dis. 69:1069, 1985. (2) C. E. Thomas et al. Cucurbit Genet. Coop. 7:126, 1984.

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