Halo Blight Research Articles

Inhibitors of Ornithine Carbamoyltransferase from [formula omitted][formula omitted] pv. [formula omitted]. st]Revised Structure of Phaseolotoxin

The structure of phaseolotoxin, a toxin produced by cultured Pseudomonassyringae pv. phaseolicola, the causal agent of halo blight disease in bean plants is revised to 3. The structure of octicidin, isolated from leaves of bean plants infected with pv. phaseolicola. has been determined to be 4, a protease degradation product of 3 which is formed in the plant.

The halo blight bacterium inhibits nodulation of dwarf beans

Infection of dwarf bean ( Phaseolus vulgaris) with a toxin-producing (Tox +) strain of the halo blight organism ( Pseudomonas syringae pv. phaseolicola) severely reduces nodulation by Rhizobium phaseoli, whereas infection with a toxin non-producing mutant does not. In vitro tests suggest that phaseolotoxin produced by the pathogen does not have a direct effect on the rhizobia.

Involvement of plasmid DNA in the productivity of coronatine by Pseudomonas syringae pv. atropurpurea.

Pseudomonas syringae pv. atropurpurea, a causal agent of halo blight of Italian ryegrass, produces coronatine (Cor) which is a toxin inducing halo blight lesions on the leaves. The relationship between Cor productivity and a specified plasmid DNA in this bactreium was studied. The plasmid of approximately 58 Mdal named as pCORl was detected in all of the 34 Cor+ wild strains tested including NIAS 1309. On the contrary, none of pCORl was detected in all of the Cor- strains obtained as spontaneous mutants from NIAS 1309 or isolated from the host plants. Furthermore, all of the 38 Cor- mutants obtained from NIAS 1309 by the treatment with acridine orange (75 to 200ppm) simultaneously lost pCORl plasmid completely. Among them, however, 29 mutants still harboured a smaller plasmid (about 40 Mdal) seemed to be a defective pCORl. These results strongly suggest that the plasmid pCORl codes Cor productivity of the bacterium.

Structure, mode of action and role in pathogenesis of the extracellular toxin of Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight of beans

Structure, mode of action and role in pathogenesis of the extracellular toxin of Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight of beans

White-seeded beans (Phaseolus vulgaris) resistant to halo blight (Pseudomonas phaseolicola), to bean common mosaic virus, and to anthracnose (Colletotrichum lindemuthianum)

SUMMARYHalo blight resistance was transferred in a backcrossing programme from PI 150414 to a Michigan-type bean. The resistant selections obtained gave yields that were up to 10% higher than that of cv. Seafarer and had seed of good quality that was suitable for baking in tomato sauce. These selections were also resistant to the common strains of bean common mosaic virus (BCMV) and to the lambda race of anthracnose.In addition, selections with white seed of similar size to Seafarer were obtained from crosses between Seafarer and cold-tolerant lines with large, coloured seeds. In trials over 4 years these selections gave 20% higher yields than Seafarer and were less sensitive to environmental changes. Like Seafarer, they were homozygous for theIgene for resistance to BCMV but were susceptible to halo blight and anthracnose. Although not as suitable for canning in tomato sauce as other material in the National Vegetable Research Station programme, they offer useful parental material for further cycles of breeding.

Halo blight strain of Pseudomonas syringae pv. mori isolated from mulberry tree in Yamanashi-ken

Halo blight strain of Pseudomonas syringae pv. mori isolated from mulberry tree in Yamanashi-ken

The effect of growing beans together with maize on the incidence of bean diseases and pests

Compared with mono-cultures, beans grown in association with maize showed generally less incidence of the following diseases and pests: halo blight, bean common mosaic, anthracnose, common blight, scab,Phoma, mildew, bolworm and to a lesser extent angular leaf spot. For white mold and the black beetleSystates the opposite was observed. Rust and aphilds were erratic in this respect.

Interactions between pseudomonads and leaves of oats, wheat and barley

Symptom development in the reportedly halo blight resistant oat line Cc 4146 and in barley, was similar to that in leaves of the susceptible oat cv. Milford following infiltration with concentrated suspensions (108 cells ml−1) of Pseudomonas coronafaciens. Resistance of barley and Cc 4146 was expressed if less concentrated inocula were used, symptoms developing more slowly or failing to appear. Susceptible responses were characterized by normo-sensitive collapse of infiltrated areas during the third day after inoculation following the rapid multiplication of P. coronafaciens. Wheat leaves were resistant to P. coronafaciens, resistance being expressed not by a hypersensitive reaction (HR) but by a slight yellowing of the inoculation site developing by 4 days after inoculation. This type of resistant reaction was also produced following infiltration of cereal leaves with other plant pathogenic bacteria P. mors-prunorum, P. phaseolicola and P. tabaci, whereas the saprophyte P. fluorescens failed to produce symptoms. Numbers of these bacteria remained relatively constant in cereal leaves. Bacteria with pathotypes of the Gramineae, P. coronafaciens (isolated from rye), P. coronafaciens var. atropurpurea and P. syringae, caused an HR in oats, wheat and barley recognized by localized collapse of leaves between 1 and 2 days after inoculation. Bacterial numbers dropped rapidly in tissue undergoing the HR. Visible collapse of leaves during hypersensitive and normosensitive responses was associated with electrolyte leakage. Induction times for hypersensitive and normosensitive collapse in oats were compared with those in broad bean, French bean and tobacco. The responses of tobacco leaves were much more rapid than other plants. Prevention of hypersensitive and normosensitive collapse in oats by prior inoculation with live or heat-killed bacteria was examined. Heat killed cells of P. coronafaciens var. atropurpurea prevented the HR and normosensitive collapse, as did live and heat-killed cells of P. tabaci. Protection was neither systemic nor light dependent.

Identification and population dynamics of bacteria in symptomatic oat leaves

Bacteria isolated from symptomatic oat leaves included pseudomonads,Erwinia herbicola, and others.Pseudomonas coronafaciens was isolated predominantly from leaves with halo blight symptoms or necrotic spots. Leaves with red leaf symptoms yielded many types of bacteria, including saprophytic pseudomonads,P. syringae, E. herbicola, Bacillus sp.,Micrococcus sp.,Corynebacterium sp., a yeast, and other unidentified species. Only isolates ofP. coronafaciens were pathogenic on the plant hosts tested. The bacteria associated with red leaf symptoms exist as saprophytes and/or epiphytes on leaves with those symptoms. It is concluded that bacteria do not contribute to red leaf symptom development in oats, but symptomatic leaves provide an environment for their growth.

Breeding for resistance to diseases in greengram and blackgram

This review is given on the origin and interrelationship of blackgram and greengram: the symptoms, mode of transmission, and host range of important diseases, namely: mungbean yellow mosaic virus, leaf crinkle virus, leaf curl virus, mosaic mottle virus, Cercospora leaf spot, powdery mildew, root and stem rots, bacterial leaf spot and halo blight. The screening for resistance, sources of resistance, including interspecific hybridization, and induced mutations, as well as the genetics of resistance are treated along with suggestions for future breeding strategies of these crops.

Phaseolotoxin : chlorosis, ornithine accumulation and inhibition of ornithine carbamoyltransferase in different plants

Phaseolotoxin, ( δ N-phosphosulphamyl) ornithylalanylhomoarginine, is the halo blight toxin produced by Pseudomonas syringae pv. phaseolicola. Application of phaseolotoxin to the leaves of ten different plant species resulted, in every case, in the accumulation of ornithine and, with one exception, this was accompanied by leaf chlorosis. Ornithine carbamoyltransferase activity from all the different plants was strongly inhibited by phaseolotoxin. In contrast, of the plants tested, pv. phaseolicola was pathogenic only on beans ( Phaseolus vulgaris). Phaseolotoxin is thus a non-specific toxin.

Survival in soil of bacteria causing common and halo blights of French bean in Victoria

Survival of Pseudomonas phaseolicola and Xanthomonas phaseoli in soil between successive bean crops was studied in a field situation at Bairnsdale. P. phaseolicola and X. phaseoli survived on nylon netting for maximum periods of 6 and 3 weeks, respectively, on the soil surface, and for 6 and 2 weeks when buried. On infected leaf, stem and pod tissue P. phaseolicola survived for 20 weeks on the soil surface and for 11 weeks when buried; X. phaseoli survived up to 11 weeks on the soil surface and for 3 weeks when buried. In heavily infected bean plots neither pathogen was carried over from one growing season to the next. It is concluded that infected bean debris in the soil from the previous growing season is not a source of common and halo blight infection in East Gippsland.

Données ultrastructurales sur l'intégration cellulaire de quelques parasites ou symbiotes de plantes. I. Procaryotes

SummaryThe present work is an ultrastructural approach of the cell integration in five different cases of Procaryotes parasitic or symbiotic in plants. It concerns two types of parasitism (the plant pathogenic Mycoplasmas and Pseudomonas phaseolicola the agent of halo-blight of bean) and three types of nitrogen-fixing symbiosis (Rhizobium of the Leguminous root-nodules, Actinomycete in the Alnus type root-nodules, Cyanophyceae of the coralloid apogeotropic roots of Cycas). Each one of these cases has a specificity based on the following points: 1) size, morphology, cell structure and taxonomic position of the microorganism;2) localization of the microorganism relatively to the plant cells, tissues and organs;3) structure of the host-microorganism interface;4) modifications which may be induced in the host-plant cells and concerning the plastids, nucleus, vacuoles, etc.;5) transformations of the microorganism during its successive life stages and eventual death in the plant;6) teratogenic or morphogenic ef...

Resistance and Seed Infection in Three Dry Bean Cultivars Exposed to a Halo Blight Epidemic

Resistance and Seed Infection in Three Dry Bean Cultivars Exposed to a Halo Blight Epidemic

N-phosphoglutamate does not behave as an active component of the exotoxin of Pseudomonas phaseolicola, the causative agent of haloblight of beans

N-phosphoglutamic acid (NPG) was chemically synthesised and characterised by electrophoretic mobility, acid lability and infra-red spectroscopy. Residual free glutamate could be removed by gel filtration through Sephadex G-15. NPG was stable in solution at neutral or alkaline pH but attempts to prepare solid NPG resulted in partial decomposition. We were unable to confirm earlier reports that NPG behaves as an active component of the exotoxin of Pseudomonas phaseolicola. In our experiments, NPG did not bring about chlorosis in bean leaves ( Phaseolus vulgaris), did not inhibit growth of Chlamydomonas reinhardi, and did not inhibit ornithine carbamyltransferase from either bean leaves or Streptococcus faecalis. In contrast, culture filtrate of Pseudomonas phaseolicola was active in all of these three tests, and contained approximately 12·5 × 10 3 units dm −3 of toxin activity.

Effect of irradiance upon the population of Pseudomonas coronafaciens in leaves and symptom expression of halo blight of rye

The toxin-induced chlorosis caused by Pseudomonas coronafaciens is influenced by irradiance. Three levels of irradiance caused differences in symptom expression but did not affect the rate of increase or final population of viable cells of P. coronafaciens in rye leaves. Distinct and faint halo blight symptoms appeared in 3--4 days in full light (1425 microW cm-2), and 58% shade (598 microW cm-2) respectively. No symptoms or only faint symptoms appeared after 7 days at 86% shade (202 microW cm-2). When plants kept in 58 and 86% shade were moved to full light 5 days after inoculation, lesion size and chlorosis increased rapidly during the next 2 days. On the 7th day after inoculation, the size of lesions from the 58 and 86% shade treatments exceeded those in full light by 2.5 and 5 times, respectively. A chlorosis index based on lesion size and chlorophyll loss within lesions also reflected this trend although chlorophyll loss was greater in lesions in full light for 7 days. Conditions of low irradiance such as that caused by overcast weather and (or) a dense leaf canopy followed by bright sunshine can cause greater losses from halo blight than a continuous period of high irradiance. Sympton expression may be masked by low irradiance but increase of inoculum is not impaired. Although increased light enhances chlorosis, toxin diffusion or production may be reduced.

Bean halo blight: comparison of phaseolotoxin and n-phosphoglutamate

Phaseolotoxin ([ n δ-phosphosulphamyl]ornithylalanylhomoarginine) and phaseotoxin A (reported to be n-phosphoglutamic acid) are compounds that have been isolated by different workers from culture filtrates of the bean halo blight organism, Pseudomonas phaseolicola. This paper compares n-phosphoglutamate with phaseolotoxin in a number of tests. n-Phosphoglutamate was much less stable than phaseolotoxin in weakly acidic or alkaline aqueous solutions and, unlike phaseolotoxin, was susceptible to hydrolysis by phosphatase. n-Phosphoglutamate was not an effective inhibitor of ornithine carbamoyltransferase, whereas phaseolotoxin gave 50% inhibition when present in the assay mixture at a concentration of 0·3 μ m. When 44 nmol n-phosphoglutamate was tested on bean leaves by the prick assay procedure, no chlorosis or ornithine accumulation resulted. In contrast 0·07 nmol phaseolotoxin gave chlorosis and ornithine accumulation, and 7 nmol led to the appearance of the systemic symptoms as well. It is concluded that n-phosphoglutamate lacks many of the properties to be expected in a bean halo blight toxin, and it is suggested that phaseotoxin A may instead be a compound related to phaseolotoxin.

Occurrence and Significance of Halo Spot (Selenophoma Donacis) on Barley in Western Australia.

Fig. 1. Halo blight on Atlas barley. RESEARCH NOTES Halo spot symptoms have been noted on barley leaves over the past two years. In 1978 it appeared in severe form at the Newdegate Research Station on barley variety Atlas . The fungus was read ily isolated using the culture techniques described by Brokenshire and Cooke (1) and Koch 's postu lates were successfully completed. Identity of the fungus was subsequently confirmed by the Commonwealth Mycological Institute (Herb. IMI 23q041) and Dr. B. M. Cooke of the University College, Dublin. The conidia produced on leaf as well as in culture were crescent shaped and unicellular. Their sizes (mean and range iniJ-Lm) were: in culture (V-8MCDA), 16.7 x 2.9 (13.0-19.5 x 2.63.9); from leaves, 18.3 x 4.2 (13.0-20.8 x 2.6-5.2). These measurements correspond closely with the description by Sprague and Johnson (7). Although this is the first record of this disease in Western Austra lia, it is possible that it has been in the State for some time, and that due to some similarity in symptoms it may have been mistaken for either scald (Rhynchosporium secalis (Oud.) J. J. Davis) or leaf spot (Drachslara vetticil/ata (O'Gara) Shoemaker). Shaw (8) identified S. dona cis stomaticola (Baumler) Sprague and Johnson on wheat in New South Wales but showed that isolates from wheat were not infective on any other gram inaceous species including barley. "There is one record of S. donacis on barley from South Australia (Collected by Dr. A. H. Mayf ield identified by Mr . J. Walker: J. Walker, personal communication. Specimen filed as DAR 28013)." Following identification of this disease, 46 entries of barley including 25 lines of the Australian Elite Nursery were inoculated at two leaf staqe using the technique of Brokenshire and Cooke (2), and assessments were made using the key devised by Cooke and Brokenshire (4). Varietal differences were not obv ious in seedlings at 2-4 leaf stage and range of mean leaf area covered var ied from 0-5 per cent. Varietal differences were however recorded at the heading stage amongst 348 breeding lines , including commercial cultivars as controls, at the Mt Barker Research Station. Varying levels of tolerance were shown with 0.9%, 4.9% and 5.7% lines classified as highly susceptible , susceptible and moderately susceptible respectively. In susceptible lines , all green leaves were almost entirely covered with lesions, and glumes and awns showed extensive browning. The observations agree with Jenkins at al (6) who found that this disease develops rapidly after ear emergence. As this disease is most severe at the time of gra in filling, under suitable conditions it could pose a major threat to barley yield in a susceptible genotype. Occurrence and Significance of Halo Spot (Selenophoma donacis) on Barley in Western Australia

Studies on the Levels of Common and Halo Blight Seed Infection Occurring in the Field.

Studies on the Levels of Common and Halo Blight Seed Infection Occurring in the Field.

Halo blight of beans: toxin production by several Pseudomonas phaseolicola isolates

Phaseolotoxin [(N δ-phosphosulphamyl)ornithylalanylhomoarginine] has recently been identified as a phytotoxin present in culture medium in which the bean halo blight organism, Pseudomonas phaseolicola, has been growing. The present paper compares the biological activity (leaf-chlorosis) with the phaseolotoxin content of such culture media. The comparison was made for isolates from a range of geographical origins, hosts and host responses. There was a close correlation between biological activity and phaseolotoxin content. When P. phaseolicola was cultured at temperatures above 18 °C, toxic activity and phaseolotoxin content of the medium decreased progressively with an increase in temperature. Phaseolotoxin production accounted for all phytotoxin activity of all isolates of P. phaseolicola examined. Phaseolotoxin production may be a useful determinative character unique to P. phaseolicola. P. glycinea produced a biologically active extract but did not produce any phaseolotoxin.