A polyphasic taxonomic study was performed on the phytopathogenic bacterial strains DAPP-PG 224(T) and DAPP-PG 228, which cause brown spot on yellow Spanish melon (Cucumis melo var. inodorus) fruits. Based on the presence of glucuronosyl ceramide (SGL-1) in cellular lipids, the results of fatty acid analysis and 16S rDNA sequence comparison, the strains had been identified as belonging to the genus Sphingomonas and as phylogenetically related to Sphingomonas mali, Sphingomonas pruni and Sphingomonas asaccharolytica. The levels of 16S rDNA sequence similarity of these three species to strain DAPP-PG 224(T) were respectively 98.0, 98.0 and 97.4%. DNA-DNA hybridization experiments between strains pathogenic on melon fruit and S. mali, S. pruni and S. asaccharolytica revealed < or = 16% relatedness. Based on these results, the two isolates studied are regarded as independent from the type strains of the three species mentioned above. Sphingomonas strains from melon fruits are recognized as forming a genetically and phenotypically discrete species and to be differentiated by phenotypic characteristics from all 29 named species of the genus. Thus, the name Sphingomonas melonis sp. nov. is proposed for the isolates from diseased melon fruits. The type strain is DAPP-PG 224(T) (= LMG 19484(T) = DSM 14444(T)). The G+C content of DNA of the type strain is 65.0 mol%.

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Brown fruit spot symptoms were observed on yellow Spanish melons (Cucumis melo var. inodorus) grown in greenhouses at Almeria in Spain. Nonsporing, motile, rod-shaped bacteria were isolated from diseased fruits, which on nutrient agar produced small yellow colonies. Two bacterial isolates, used for further investigations, were pathogenic on fruits but not on cotyledons of Spanish melon plants. They provoked disease symptoms similar to those observed in the greenhouse. Both isolates were Gram-negative, catalase-positive, weakly oxidase-positive and phenylalanine deaminase-negative. They hydrolysed esculin but not gelatin and they utilized glucose oxidatively. Fatty acid analysis revealed that both isolates belong to the genus Sphingomonas. In addition, 16S rDNA sequence analysis, performed on one isolate, demonstrated that it had a significant sequence similarity (more than 98%) with Sphingomonas pruni and Sphingomonas mali, nonphytopathogenic bacteria isolated from plants. Although enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic PCR seem to indicate that the Sphingomonas isolates from Spanish melon fruits may belong to a new species, DNA±DNA hydridization analysis is necessary to verify this hypothesis.

During the period of May to August 2002, typical symptoms of downy mildew were observed on squash (Cucurbita pepo L.) in both tunnel and open field cultivation in central Italy (Latium and Umbria). The disease spread rapidly and because the control measures used were not effective, growers suffered severe yield losses. Infected plants showed yellow spots on the upper leaf surface. Based on morphological features observed at ×10 to ×40 magnification, the pathogen was identified as Pseudoperonospora cubensis (Berk. & M.A. Curtis) Rostovzev. To verify the pathogenicity of the fungus, a sporangial suspension (1 × 104 sporangia per ml) was sprayed on leaves of squash plants with two expanded leaves, which were held in dark moist chambers at 20 ± 2°C for 48 h. Control plants were sprayed with sterile water. Inoculated and control plants were kept in a growth chamber at 24 ± 2°C with 14/10 h day/night cycles. Chlorotic spots and sporulation were observed on inoculated plants. The morphological features of the fungus obtained from the inoculated plants were identical to those from the original diseased plant. Previous observations of downy mildew in Italy suggested that squash was not susceptible (1). The physiological specialization among isolates of P. cubensis based on the compatibility of different cucurbit hosts (2) was not tested previously in Italy. To determine the pathotype of four fungal isolates obtained from squash cultivated in different localities, 10 plants per species of the cucurbit species (2) were inoculated with each isolate using the same procedure described for the pathogenicity test. Disease symptoms were detected on all inoculated hosts, including squash, suggesting that all the fungal isolates obtained from squash are pathotype 5. Only pathotype 5 is a common causal agent of downy mildew of squash and other cucurbit hosts. During the period of our observations, climatic conditions were unusually wet because frequent storms occurred during the summer providing favorable environmental conditions for the development of secondary spread. Today, it appears there are no commercially acceptable cultivars of squash resistant to downy mildew available to growers in Italy. References: (1) F. Ciccarese et al. Phytopathol. Mediterr. 29:14, 1990. (2) C. E. Thomas et al. Phytopathology 77:1621, 1987.

Bacterial speck symptoms on leaves of the tomato cultivar Erminia Fl (Petoseed), heterozygous for the Pto resistant gene, were observed in June 1995 in Northern Italy. Using individual-lesion isolation, 8 bacterial isolates were obtained from the affected leaves, which were identified as Pseudomonas syringae pv. tomato by biochemical, physiological, nutritional and pathogenicity tests. When the differential cultivar Otitario 7710, homozygous for the Pto gene, was inoculated with the bacterial isolates, 4 of them provoked the typical bacterial speck symptoms and therefore belonged to race 1. This is the first occurrence of P. syringae pv. tomato race 1 in Italy and the first time this race has been isolated on a Pto gene-bearing tomato cultivar grown in open field. Zusammenfassung DasVorkommen von Pseudomonas syringae pv. tomato Rasse 1 in Itatien an Tomatenpflanzen mit dem Pto-Gen Im Juni 1995 wurden in Nortalien Symptome der Tupfelschwarze an Blattern der Tomatensorte Erminia Fl (Petoseed), die fur das Pto Resistenzgen heterozygotisch ist, beobachtet. Aus einzeinen Blattlasionen wurden 8 Bakterienisolate gewonnen, die anhand von biochemischen, physiologischen, Nahrmediumverwertungssowie Pathogenitatstests als Pseudomonas syringae pv. tomato bestimmt werden konnten. Nach einer Inokulation der Differentialsorte Ontario 7710, die filr das Pto-Gtn homozygotisch ist., mit diesen Baktedenisolaten wurden Syptome der Tupfelschwarze durch 4 Isolate hervorgerufen, ein Zeichen dafur, dafi diese Isolate zu Rasse 1 gehoren. Damit wird zum ersten Mai tiber das Vorkommen von P. syringae pv. tomato in Itahen und uber die Isolierung dieser Rasse aus einer im Freiland wachsenden Tomatensorte mit dem Pjo-Gen beschrieben.