摘要:

In order to explain the occurrence of very severe or more moderate wilt of grasses attacked byXanthomonas campestrispv.graminis, various observations on the factors possibly influencing the epidemics of the disease are summarized in this article. Although natural vectors exist, the main means of transmission is certainly mowing tools. Resistance of the plants can be genetically predetermined or induced by non‐pathogenic phyllosphere bacteria, if these are inoculated at the same time as the pathogen and in sufficient numbers. Young seedlings are particularly susceptible. Strains ofX.c. graminisvary in their pathogenicity. Non‐pathogenic strains enhance host resistance. Very severe attacks are related to extremely virulent strains. Crop management can influence the disease which is favoured by various stress situations. Disease spreads extensively when grass is mown under wet conditions. In conclusion, the following measures are recommended to avoid heavy attacks: use of resistant grass cultivars; avoiding contaminated mowing tools, especially for the first cut; cutting under dry conditi

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00133.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Bacterial streak caused by ‘Xanthomonas translucens’ is a serious bacterial disease of wheat and triticale and is distributed worldwide. Contaminated seed is the main source of inoculum. As disease incidence appears to be increasing in several countries, research is needed for more resistance in both crops. However, assessment of resistance is hampered by symptom variations and diagnosis can be difficult. Moreover, the nomenclature of the pathogens causing bacterial streak on cereals is rather confusing. A seed detection method has been developed at CIMMYT (Centro Internacional de Mejoramiento de Maiz y Trigo) using a WBC semi‐selective medium. The efficiency of hot cupric acetate has been confirmed to disinfect contaminated seed sets. More research is currently under way on epidemiology to identify the environmental factors favorable for disease expression and to determine the transmission rate of bacteria under Mexican condi

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00134.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Multiplication of the rye‐specific and barley‐specific pathovarssecalisandtranslucens, respectively, ofXanthomonas campestris(earlier namedXanthomonas translucensf. sp.cerealis)was determined in two rye and two barley cultivars. Fresh bacterial cultures were suspended in boiled tap water, adjusted to about 3 × 107cfu ml−1and infiltrated into the mesophyll of young leaves. In the compatible combinations, a generation time of 1.7–2.1 h was determined. Significantly higher multiplication rates than in incompatible combinations were not observed before 3 or 4 days after inoculation. At this time, the first small water‐soaked areas appeared. Bacteria multiplied up to the seventh day after inoculation, reaching a maximum of at least 109cells per cm2, the same time at which the water‐soaked areas had reached their maximum size. Thus, the rate of bacterial multiplication paralleled with the development of the water‐soaked areas. In the incompatible combinations, nearly the same generation times were detected during the exponential growth phase. However, water‐soaked areas did not appear, and the final bacterial concentration ranged from 1:1000 to 1:100 of that determined in compatible combinations. A distinct early lag phase, characterized by a decrease of the bacterial population down to 1:100 of the starting concentration, was detec

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00135.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Bacterial leaf streaks of wheat and barley in Kerman province (Iran) were found to be distinct in etiology. The barley strains were limited in host range and could only infect barley. The wheat strains were pathogenic to barley, wheat, rye, triticale,Bromusspp.,Agropyronspp.,Elymus junceus, Lolium multiflorum, andPhalaris tuberosa, but notDactylis glomerata, Cynodon dactylon, Phleum pratense, and oat. Based on host reactions and electrophoretic patterns of cell proteins, the barley and wheat strains were identified asXanthomonas campestrispv.hordeiand pv.cerealis, respectively.

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00136.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A survey in 1987 and 1988 revealed that basal glume rot, caused byPseudomonas syringaepv.atrofaciens, occurred nearly everywhere in FRG. The symptoms of the disease usually consisted of water‐soaked dark green to brown lesions on unripe wheat heads, mainly at the basal end of the glumes, which later became dark brown. Forty‐six isolates ofP.s. atrofacienswere obtained from glumes, seeds and leaves of wheat and barley. For a fast identification of the isolated bacteria, a bio‐assay was developed. Four to five‐day‐old wheat seedlings, grown on wet filter paper in Petri dishes, were pricked at two‐three sites with a dissecting needle contaminated with bacteria. After 2–3 days, pathogenic isolates induced brown to black spots. The bacterial isolates from wheat inhibited the growth of several fungi grown on potato dextrose agar. In contrast, an authentic isolate ofP.s. syringaeobtained from wheat showed no inhibitory effect. During screening for resistance, several cultivars of spring and winter wheat were tested in the greenhouse and/or field tests. The results revealed marked differences in the susceptibility of differ

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Bacterial leaf streak and black chaff is a seed‐transmitted disease of cereals caused byXanthomonas campestrispv.translucens. The bacterium can be identified by its slow growth, slime production, yellow pigment, beta‐galactosidase production, and ice nucleation activity. Aspects of resistance, dissemination, symptoms, and distribution are discus

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Bien que la culture des graminées soit trés importante en Espagne, nous n'avons constaté que quelques problèmes posés par des bactéries phytopathogènes, sur maïs et orge. En 1980 nous avons étudié une maladie du maïs dans une culture porte‐graines du cv. Rx‐90, à partir duquel nous avons isoléErwinia chrysanthetni.La même maladie était connue depuis quelques années sur cultivars ayant un cycle de 700 FAO, cultivés dans des champs arrosés par aspersion. Ľaddition de chlore àľeau ďirrigation a empêché la propagation de la bactérie. A une seule occasion, nous avons isolé une bactérie, identifyée comme ‘Xanthomonas translucens”, dans un champ ďorge provenant de semences importées. Les études sur le potentiel pathogène de la souche, réalisées par inoculation sur différents hôtes, ont permis ďidentifier la forme spécifique

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The economic importance ofXanthomonas campestrispv.graminison grasses has made it necessary to look for control measures. The most important is breeding for resistance. Different methods of selection were investigated and compared. Further, production of the inoculum, virulence, host specificity, disease assessment and yield losses ofArrhenatherum elatiuswere examined.

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Isolates ofXanthomonas campestrispv.graminisare known to vary in pathogenicity, which may be lost more or less rapidly in culture on artificial media. Inoculation ofLolium multiflorumwith mixtures of a highly pathogenic strain and increasing proportions of a nonpathogenic strain ofX. c. graminisresulted in a decreasing disease expression and mortality. Re‐isolation from plants inoculated with 1% pathogenic and 99% non‐pathogenic bacteria resulted mostly in highly pathogenic monobacterial colonies. Of about 200 colonies, 3% were non‐pathogenic. A few isolates had an intermediate pathogenicity. It has not been established whether they were pure strains or mixtures of pathogenic and non‐pathogenic bacteria. All isolates from plants inoculated with the non‐pathogenic strain were non‐pathogenic. The nonpathogenic bacteria multiplied inside the plants, but they were mostly found in the inoculated leaves. Thirty pots containing each about 20 plants of Italian ryegrass were pre‐inoculated with non‐pathogenic strains and, 4 weeks later, they were cut with scissors contaminated by pathogenicX. c. graminis. The disease was highly reduced in about half of the pots. Further experiments are needed to judge the expediency of such a ‘premun

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

14 cultivars de raygrass ďltalie ont été inoculés artificiellement au champ parXanthomonas campestrispv.graminis.La corrélation entre les notes de flétrissement et les pertes de rendement causees par le parasite est satisfaisante: 0,7371 (P<0,01). Le cultivar le plus résistant était Turilo car sa perte de rendement était nulle. Mais les symptômes de flétrissement causés parX.c. graminisétaient décelables sur ce cultivar (10% des feuilles flétries). Tiara était le cultivar le plus sensible: il a subi 47% de pertes et plus de la moitié des feuilles étaient flétries. Des inoculations en serre ont été répétées trois fois sur 11 de ces cultivars. Leurs classements suivant leur sensibilité a ľinfection étaient voisins mais non parfaitement constants: les significations des corrélations 2 à 2 varient (0,5

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1989.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY