Interactions of the bean rust and cowpea rust fungi with species of the Phaseolus – Vigna plant complex. I. Fungal growth and development

1987 ◽  
Vol 65 (6) ◽  
pp. 1096-1107 ◽  
Author(s):  
Janice F. Elmhirst ◽  
Michèle C. Heath

Growth and development of two closely related rust fungi, Uromyces appendiculatus and U. vignae (uredospore infections), were compared in several American and African species of the Phaseolus – Vigna plant complex and in Lablab purpureus. In plants inoculated with U. appendiculatus the frequency of formation of both primary and secondary haustoria generally decreased with evolutionary distance from the American host species. Uromyces appendiculatus formed primary haustoria at a high frequency of infection sites in most American and many African species, and also sustained a limited haustorium – plant cell metabolic relationship (as determined by the amount of secondary fungal growth) in one group of African species. Uromyces vignae generally formed very few haustoria in both American and African species not known as hosts of the fungus; however, growth of U. vignae colonies occasionally continued for some time at a few infection sites in nonhost species without sporulation. The implications of these results are discussed with respect to the coevolution of the two fungi with their hosts.


1988 ◽  
Vol 1 (4) ◽  
pp. 363
Author(s):  
JAG Irwin

Morphological studies on the rust fungi of Macroptilium, Phaseolus and Vigna show that three taxa can be distinguished. The Vigna rust, Uromyces vignae, is maintained as a species distinct from the bean rust, U. appendiculatus var. appendiculatus. A new variety, Uromyces appendiculatus (Pers.) Unger var. crassitunicatus J. Irwin, is described from Macroptilium atropurpureum. It differs from var. appendiculatus in having urediniospores with thicker side walls and more closely spaced echinulae. The teliospores are similar to those of var. appendiculatus, except that the side walls are thicker; the side walls are darker, with lineal rows of warts over the entire surface, and a conspicuous channel in the base; the hyaline apical thickening is thinner; and pedicels are more broadly attached.



2001 ◽  
Vol 79 (5) ◽  
pp. 570-577 ◽  
Author(s):  
James E Eckenwalder ◽  
Michèle C Heath

We explored the association between the phylogeny of 14 species of beans in the genera Phaseolus and Vigna (subtribe Phaseolinae) and the progress of infections in them caused by two pathogenic rust fungi, Uromyces appendiculatus (Pers.) Unger and Uromyces vignae Barclay. The analyses involved construction of phenograms, ordinations, and cladograms derived from the infection characteristics and their comparison to a composite of three previously published DNA phylogenies. The patterns of infection by U. vignae showed no relationship to the phylogeny of the infected plants. The course of infection by U. appendiculatus, however, displayed a significant phylogenetic component, although the defense responses of the infected plants themselves did not. These differences in phylogenetic signal between infections caused by the two fungi may reflect distinct evolutionary histories with members of the Phaseolinae, a long association for U. appendiculatus but a much more recent one for the more host-specific U. vignae.Key words: bean rust, cowpea rust, evolution, infection characteristics, Phaseolus, Vigna.



1989 ◽  
Vol 67 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Janice F. Elmhirst ◽  
Michèle C. Heath

A comparison of the histological responses of species within the Phaseolus–Vigna plant complex to single isolates of the bean and cowpea rust fungi revealed that no particular response was restricted to any plant taxonomic group, although species differed in the proportion of infection sites at which a particular response was exhibited. Related species did not always show similar frequencies of responses and sometimes there were differences between different genotypes within a nonhost species. In host and nonhost species, preinoculation heat treatment commonly inhibited prehaustorial defenses and delayed the death of the invaded cell. Growing fungal colonies subsequently developed in many species, even those considered nonhosts, particularly if they exhibited a high frequency of prehaustorial defenses in untreated leaves. It is argued that a lack of heat-induced colony formation is a sign of parasite-specific resistance, which most likely evolved only in originally susceptible plants. Consequently, the data suggest that the bean rust fungus has had a long association with American species of the complex and that extant nonhost species may have evolved from susceptible ancestors. In contrast, the cowpea rust fungus appears to have had little evolutionary contact with these American species and may not be as closely related to the bean rust fungus as originally thought.



Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 143
Author(s):  
Vera Breiing ◽  
Jennifer Hillmer ◽  
Christina Schmidt ◽  
Michael Petry ◽  
Brigitte Behrends ◽  
...  

As biorationals, plant oils offer numerous advantages such as being natural products, with low ecotoxicological side effects, and high biodegradability. In particular, drying glyceride plant oils, which are rich in unsaturated fatty acids, might be promising candidates for a more sustainable approach in the discussion about plant protection and the environment. Based on this, we tested the protective and curative efficacy of an oil-in-water-emulsion preparation using drying plant oils (linseed oil, tung oil) and a semi-drying plant oil (rapeseed oil) separately and in different mixtures. Plant oils were tested in greenhouse experiments (in vivo) on green beans (Phaseolus vulgaris L.) against bean rust (Uromyces appendiculatus). We observed that a 2% oil concentration showed no or very low phytotoxic effects on green beans. Both tested drying oils showed a protective control ranging from 53–100% for linseed oil and 32–100% for tung oil. Longer time intervals of 6 days before inoculation (6dbi) were less effective than shorter intervals of 2dbi. Curative efficacies were lower with a maximum of 51% for both oils when applied 4 days past inoculation (4dpi) with the fungus. Furthermore, the results showed no systemic effects. These results underline the potential of drying plant oils as biorationals in sustainable plant protection strategies.



1994 ◽  
Vol 124 (2) ◽  
pp. 341-350 ◽  
Author(s):  
B R EDINGTON ◽  
P E SHANAHAN ◽  
F H J RIJKENBERG


Plant Disease ◽  
1999 ◽  
Vol 83 (2) ◽  
pp. 108-113 ◽  
Author(s):  
Craig M. Sandlin ◽  
James R. Steadman ◽  
Carlos M. Araya ◽  
Dermot P. Coyne

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.



2021 ◽  
Vol 75 (1) ◽  
pp. 583-607
Author(s):  
Devanshi Khokhani ◽  
Cristobal Carrera Carriel ◽  
Shivangi Vayla ◽  
Thomas B. Irving ◽  
Christina Stonoha-Arther ◽  
...  

Chitin is a structural polymer in many eukaryotes. Many organisms can degrade chitin to defend against chitinous pathogens or use chitin oligomers as food. Beneficial microorganisms like nitrogen-fixing symbiotic rhizobia and mycorrhizal fungi produce chitin-based signal molecules called lipo-chitooligosaccharides (LCOs) and short chitin oligomers to initiate a symbiotic relationship with their compatible hosts and exchange nutrients. A recent study revealed that a broad range of fungi produce LCOs and chitooligosaccharides (COs), suggesting that these signaling molecules are not limited to beneficial microbes. The fungal LCOs also affect fungal growth and development, indicating that the roles of LCOs beyond symbiosis and LCO production may predate mycorrhizal symbiosis. This review describes the diverse structures of chitin; their perception by eukaryotes and prokaryotes; and their roles in symbiotic interactions, defense, and microbe-microbe interactions. We also discuss potential strategies of fungi to synthesize LCOs and their roles in fungi with different lifestyles.



1996 ◽  
Vol 29 (2) ◽  
pp. 159-167 ◽  
Author(s):  
J. P. Martinez ◽  
J. V. Groth ◽  
N. D. Young


1997 ◽  
Vol 78 (3) ◽  
pp. 1222-1236 ◽  
Author(s):  
Ranjan Batra ◽  
Shigeyuki Kuwada ◽  
Douglas C. Fitzpatrick

Batra, Ranjan, Shigeyuki Kuwada, and Douglas C. Fitzpatrick. Sensitivity to interaural temporal disparities of low- and high-frequency neurons in the superior olivary complex. I. Heterogeneity of responses. J. Neurophysiol. 78: 1222–1236, 1997. Interaural temporal disparities (ITDs) are a cue for localization of sounds along the azimuth. Listeners can detect ITDs in the fine structure of low-frequency sounds and also in the envelopes of high-frequency sounds. Sensitivity to ITDs originates in the main nuclei of the superior olivary complex (SOC), the medial and lateral superior olives (MSO and LSO, respectively). This sensitivity is believed to arise from bilateral excitation converging on neurons of the MSO and ipsilateral excitation converging with contralateral inhibition on neurons of the LSO. Here we investigate whether the sensitivity of neurons in the SOC to ITDs can be adequately explained by one of these two mechanisms. Single and multiple units ( n = 124) were studied extracellularly in the SOC of unanesthetized rabbits. We found units that were sensitive to ITDs in the fine structure of low-frequency (<2 kHz) tones and also units that were sensitive to ITDs in the envelopes of sinusoidally amplitude-modulated high-frequency tones. For both categories there were “peak-type” units that discharged maximally at a particular ITD across frequencies or modulation frequencies. These units were consistent with an MSO-type mechanism. There were also “trough-type” units that discharged minimally at a particular ITD. These units were consistent with an LSO-type mechanism. There was a general trend for peak-type units to be located in the vicinity of the MSO and for trough-type units to be located in the vicinity of the LSO. Units of both types appeared to encode ITDs within the estimated free-field range of the rabbit (±300 μs). Many units had varying degrees of irregularities in their responses, which manifested themselves in one of two ways. First, for some units there was no ITD at which the response was consistently maximal or minimal across frequencies. Instead there was an ITD at which the unit consistently responded at some intermediate level. Second, a unit could display considerable jitter from frequency to frequency in the ITD at which it responded maximally or minimally. Units with irregular responses had properties that were continuous with those of other units. They therefore appeared to be variants of peak- and trough-type units. The irregular responses could be modeled by assuming additional phase-locked inputs to a neuron in the MSO or LSO. The function of irregularities may be to shift the ITD sensitivity of a neuron without requiring changes in the anatomic delays of its inputs.



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