Bean Rust Fungus Uromyces Appendiculatus Research Articles

Control of the bean rust fungus Uromyces appendiculatus by means of Trichoderma harzianum: leaf disc assays on the antibiotic effect of spore suspensions and culture filtrates

Several species of the fungal genus Trichoderma act as antagonists of other fungi. A number of strains from the Trichoderma species T. harzianum Rifai are used as biological control agents for the control of soilborne as well as foliar plant pathogens. Six T. harzianum strains, five of them isolated from commercial preparations, were evaluated for their capability to control the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger. Different kinds of leaf disc assays were performed with conidial spore suspensions and sterile culture filtrates of the T. harzianum strains. Great differences were observed concerning the efficacy of the Trichoderma strains to reduce the number of the uredial pustules developing after rust inoculation which followed the application of the particular Trichoderma strains. Efficacy values ranged from 1 to over 50%. Increasing spore or culture filtrate concentrations of the two most effective isolates T12 and TU led to decreases in the number of developing uredial pustules. Culture filtrate applications had a protective but no curative effect. T12 spore suspensions maintained their disease reducing activity even when autoclaved. This and some other evidence for an antibiotic interaction between T. harzianum and U. appendiculatus are discussed.

Transient transformation of the rust fungus Puccinia graminis f. sp. tritici.

The biotrophic rust fungus Puccinia graminis f. sp. tritici (Pgt) was transformed by particle bombardment. The promoter from the Pgt translation elongation factor 1alpha (EF-1alpha) gene was fused to the bacterial marker genes hygromycin B phosphotransferase (hpt) and beta-glucuronidase (GUS). Transformation constructs were introduced into uredospores of Pgt, an obligate pathogen of wheat, by biolistic bombardment. Uredospores transformed with the construct containing the hpt gene germinated and initiated branching on selective medium, indicating that they had acquired resistance to hygromycin B. However, transformants stopped growing 5 days after bombardment. GUS activity in uredospores and germlings was histochemically detected 4-16 h after bombardment. GUS expression was also obtained using the INF24 promoter from the bean rust fungus Uromyces appendiculatus, demonstrating that heterologous genes can be expressed in P. graminis under the control of regulatory sequences from closely related organisms.

Isolates of Uromyces appendiculatus with Specific Virulence to Landraces of Phaseolus vulgaris of Andean Origin.

Five isolates of the bean rust fungus Uromyces appendiculatus were shown to be specifically virulent on bean genotypes of Andean origin. This specificity was demonstrated by the virulence of five pairs of isolates on a differential set of 30 Phaseolus vulgaris landraces. Each isolate pair was from a different country in the Americas and consisted of one Andean-specific isolate and one nonspecific isolate. Of the differential P. vulgaris landraces, 15 were of Middle American origin and 15 were of Andean origin. The Andean-specific rust isolates were highly virulent on Andean landraces but not on landraces of Middle American origin. Rust isolates with virulence to Middle American landraces were also generally virulent on Andean material; no truly Middle American-specific isolates were found. Random amplified polymorphic DNA (RAPD) analysis of the rust isolates also distinguished the two groups. Four of the Andean-specific rust isolates formed a distinct group compared to four of the nonspecific isolates. Two of the isolates, one from each of the two virulence groups, had intermediate RAPD banding patterns, suggesting that plasmagomy but not karyogamy occurred between isolates of the two groups.

Changes in Metabolite Pools in Host and Pathogen during the Uredinio and Teliospore Development of the Bean Rust Fungus Uromyces appendiculatus

AbstractMetabolite pool sizes as well as indications for changes in the translocation of metabolites from the host to the parasite were investigated on primary leaves of decapitated bean plants infected with the bean rust fungus Uromyces appendiculatus var. appendiculatus (Pers.) Link with respect to changes in the spore type from uredinioto teliospores. Noninfected control leaves were compared to the directly influenced sorus region of infected leaves and the mycelium‐free areas of these leaves (‘leaf‐remainder’).The data show evidence for an intensive change in the metabolite pools, indicating translocation from the metabolically active leaf‐remainder to the sori, expressing characteristic changes according to the spore type produced. The importance of single metabolites and changes in their pool sizes is discussed and correlated to the respective pools within the uredinio‐ and teliospores. The data indicate that vegetative urediniospores contain mainly preformed metabolites and precursors, whereas teliospores need to undergo metabolite syntheses before germination.

Incomplete Dominance of Rust Resistance in Tepary Bean

Foliar diseases are a major constraint to cultivated tepary bean (Phaseolus acutifolius A. Gray var. latifolius Freeman) production in some environments. The reactions of 12 cultivated teparies to eight individual races (41, 47, 49, 51, 53, 58, 67, and 73) of the bean rust fungus Uromyces appendiculatus (Pers.) Unger var. appendiculatus maintained at Beltsville, Md., were examined under greenhouse conditions. These diverse races, used together, overcome all of the major rust-resistance genes present within the 19 host differential cultivars of common bean (Phaseolus vulgaris L.). Seven lines (GN-605-s, GN-610-s, PI 321638-s, PI 502217-s, Neb-T-6-s, Neb-T-8a-s, and Neb-T-15-s) exhibited similarly high levels of resistance (immunity or necrotic spots without sporulation) to all eight races. Inheritance of resistance was examined across five susceptible × resistant (S × R) and three resistant × resistant (R × R) populations. The rust reactions in the F1, F2, and F3 generations derived from S × R crosses revealed that the immune or necrotic resistance response was conditioned by a single locus exhibiting incomplete dominance. The rust resistance of four lines tested for allelism in R × R crosses was found to be derived from the same gene. This apparent lack of variability for rust resistance suggests that a single introgression event may realize the full potential for cultivated tepary bean to contribute rust resistance to common bean through interspecific hybridization. In addition, the limited variability for resistance to the highly variable rust pathogen in cultivated tepary bean supports the occurrence of a “bottleneck effect” during domestication of this species, as observed in germplasm diversity studies.

Superoxide Dismutase: A Differentiation Protein Expressed in Uromyces Germlings during Early Appressorium Development

Lamboy, J. S., Staples, R. C., and Hoch H. C. 1995. Superoxide dismutase: A differentiation protein expressed in Uromyces germlings during early appressorium development. Experimental Mycology 19, 284-296. Germlings of the bean rust fungus Uromyces appendiculatus detect penetration sites on the surface of the host leaf by thigmosensing topographical features. Within 2-4 min after the apex of a urediospore germ tube encounters the cuticular lip of a stomate, the germling ceases polarized growth and begins to swell over the aperture. The mechanism by which the cells detect topographical signals is not understood; however, previous experiments indicated that the initiation process does not involve de novo gene expression. In order to detect posttranslational modifications, the protein profiles of induced and noninduced germlings were compared at the earliest stages of appressorium formation, and a 21-kDa differentiation protein was identified by a shift in isoelectric point. The N-terminal amino acid sequence exhibited homology with superoxide dismutase (SOD), and antibodies to a synthetic peptide fragment of the respective sequence recognized cooper/zinc isozymes of SOD in electroblots of native gels. Electroelution of the active enzyme bands and separation by SDS-PAGE indicated that the 21-kDa protein is a component of a tetrameric 85-kDa SOD.

Coupling- and repulsion-phase RAPDs for marker-assisted selection of PI 181996 rust resistance in common bean

The Guatemalan black bean (Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20490 tightly linked (no recombinants) in coupling phase and OAE19890 linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC4F2 (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC4F2 and 57 BC4F3 individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20490 and OAE19890 was investigated in a diverse group of common bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20490. A RAPD similar in size to OAC20490, observed in some susceptible common bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20490. Use of the RAPDs OAC20490 and OAE19890 in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BCnF1individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F2 or later-segregating generations.

DNA Markers Reveal Hybrids Between Two Diverse Background Genotypes in Australian Collections of the Bean Rust Fungus Uromyces appendiculatus

Two classes of molecular markers, RFLPs (restriction fragment length polymorphisms) and RAPDs (random amplified polymorphic DNA) were used to assess genetic diversity among Australian bean rust isolates (Uromyces appendiculatus (Pers.) Unger var. appendiculatus) collected from diverse geographic locations spanning the period 1973-1990. Initially we screened 22 isolates using WLPs from five DNA probes. This was followed by analysis of a subset of 12 of these isolates using RFLPs from 10 cDNA probes and RAPDs from 10 arbitrary primers for a comprehensive evaluation of background genotype. Polymorphic bands revealed the existence of two divergent clusters of isolates, representing genotypes designated A and B. The RFLP markers showed 30% band dissimilarity between A and B, and RAPDs 16% dissimilarity. Isolates in a third cluster (genotype AB) exhibited most of the polymorphic bands present in A and B, but no unique polymorphic bands of their own, indicating that they had most probably arisen from recent hybridisation between isolates of genotype A and B. The subset of 12 isolates included 10 race phenotypes, but no clear correlation between background genotype (as assessed by RFLP and RAPD markers) and race phenotype was evident. We suggest that Australian races of bean rust have most probably evolved by a combination of mutation to virulence from common A and B background genotypes, and genetic recombination.

Secretion systems and membrane-associated structures in rust fungi after high pressure freezing and freeze-fracturing

Excellent preservation and new structural details can be demonstrated in rust-infected leaf tissue after high pressure freezing and freeze-fracturing. A tubular-vesicular complex was the most remarkable cytoplasmic structure observed in cells of the bean rust fungus Uromyces appendiculatus var. appendiculatus during its establishement in its host Phaseolus vulgaris. In fungal cells undergoing intensive synthesis of wall material, this membranous system extended throughout the cytoplasm; in addition, vesicles were accumulated adjacent to the plasma membrane. Here, membrane-associated configurations were observed which seem to be involved in exo- and/or endocytotic processes. It is assumed that the tubular-vesicular complex belongs to the endomembraneous system of the bean rust fungus and that it is involved in the synthesis and secretion of wall material.

Cell-substratum adhesive protein involved in surface contact responses of the bean rust fungus

Uredospore germlings of the bean rust fungus Uromyces appendiculatus display two contact-sensitive responses on leaves or certain synthetic surfaces: a specific orientation of germ tubes and an induction of appressoria at leaf stomates or scratched surfaces. Germ tube orientation, nuclear division (used as a marker for appressorium formation) and germling adhesion on scratched “Parafilm” was reduced by the proteolytic enzyme, pronasc E (ED 50 = 20–50 μg ml −1), but not by the heat denatured proteolytic enzyme. Forty micrograms of pronase E per millilitre significantly reduced nuclear division of germlings incubated on either a hydrophilic or a hydrophobic surface. Pronase E reduced adhesion regardless of whether the enzyme was applied during growth or after attachment had occurred, although higher concentrations were required after attachment had occurred. The data suggest that extracellular protein is required for germling adhesion to a substratum and that adhesion is required for germ tube orientation and thigmodifferentiation. We partially characterized the composition of the bean rust extracellular material and analyzed for proteins on SDS-polyacrylamide gels. Intact germlings have six predominant extracellular peptides detected by 125I labelling. Spent culture fluid contains several different peptides; four of the five major peptides in the spent culture fluid are glycosylated.

Einsatz von V. lecanii als biologisches Schädlingsbekämpfungsmittel gegen den Bohnenrostpilz U. appendiculatus var. appendiculatus im Feld und im Gewächshaus

Abstract The use of Verticillium lecanii as a biological control agent against the bean rust fungus Uromyces appendiculatus var. appendiculatus in the field and in the glasshouse The deuteromycete V. lecanii parasites uredo‐ and teliospores of the bean‐rust‐fungus U. appendiculatus var. appendiculatus. We investigated the conditions for the use of the hyperparasite as biological control agent in the field and in glasshouses.The growth rate of the hyperparasite was 0,3 cm per day at 25 °C. Under suitable conditions in the lab (25 °C, 100 % r. h.) it took about 20 days to invade 100 % of uredospores and 65 % of teliospores.We failed to prevent the spread of bean‐rust‐fungus spores in the field, but we succeeded in the glasshouse by 68 %, compared to the untreated controls, using the hyperparasite V. lecanii as biological control agent.