Genetic and Morphological Diversity of Temperate and Tropical Isolates of Phytophthora capsici.

ABSTRACT Phytophthora capsici is a diverse species causing disease on a broad range of both temperate and tropical plants. In this study, we used cultural characteristics, amplified fragment length polymorphism (AFLP), and DNA sequence analyses of the ribosomal internal transcribed spacer (ITS) region and mitochondrial cytochrome oxidase II (cox II) genes to characterize temperate and tropical isolates from a wide range of host species. All but one temperate isolate grew at 35 degrees C, while all tropical isolates did not. All but two tropical isolates formed chlamydospores, while temperate isolates did not. There was strong bootstrap support for separation of temperate and tropical isolates using AFLP analysis; however, the temperate isolates appeared as a subgroup within the observed variation of the tropical isolates. The majority of temperate isolates clustered within a single clade with low variation regardless of host or geographical origin, while the tropical isolates were more variable and grouped into three distinct clades. Two clades of tropical isolates grouped together and were affiliated closely with the temperate isolates, while the third tropical clade was more distantly related. Phylogenetic analysis of the ITS regions resulted in similar groupings and variation within and between the temperate and tropical isolates as with the AFLP results. Sequence divergence among isolates and clades was low, with more variation within the tropical isolates than within the temperate isolates. Analysis of other species revealed shorter branch lengths separating temperate and tropical isolates than were observed in comparisons among other phylogenetically closely related species in the genus. Analysis of cox II sequence data was less clear. Although the temperate and tropical isolates grouped together apart from other species, there was no bootstrap support for separating these isolates. Restriction fragment length polymorphism (RFLP) analysis of the ITS regions separated the temperate and tropical isolates, as in the AFLP and ITS phylogenetic analyses. However, RFLP analysis of the cox I and II gene cluster did not distinguish between temperate and tropical isolates. The differences in grouping of isolates in these two RFLP studies should be helpful in identifying isolate subgroups. Our data do not fully clarify whether or not temperate and tropical isolates should be separated into different species. The available worldwide data are incomplete and the full range of variation in the species is not yet known. We suggest refraining from using the epithet P. tropicalis until more data are available.

Quantitative relationships among thaxtomin A production, potato scab severity, and fatty acid composition in Streptomyces.

Thaxtomin A production in culture, potato common scab severity (percentage of tuber surface infected or number of lesions per tuber), and fatty acid profiles were determined for 78 Streptomyces isolates. Only pathogenic Streptomyces spp. (n = 17) produced thaxtomin A in culture. Thaxtomin A production in culture (microgram/mL) was significantly positively correlated with the percentage of tuber surface infected (R = 0.60; p = 0.017) but not with the number of lesions per tuber (R = 0.37; p = 0.17). An increase of 1 microgram/mL in thaxtomin A production corresponded to an 11% increase in disease severity (percentage of tuber surface infected). The data indicate that quantitative information on the ability of a particular pathogen isolate or population to produce thaxtomin A may be critical to understanding and predicting the disease potential of that population. Using cluster analysis of fatty acid data, 94% of 67 unknown field isolates grouped with other field isolates having the same pathogenicity (plus or minus).

Use of repetitive intergenic DNA sequences to classify pathogenic and disease-suppressive Streptomyces strains.

PCR DNA fingerprinting using repetitive intergenic DNA sequences (rep-PCR) was investigated as a means of differentiating between closely related strains of Streptomyces which were, in some cases, indistinguishable by other classification methods. Our results demonstrated that the majority of strains had unique rep-PCR DNA fingerprints and established that the technique could be a very useful tool in rapidly determining strain identity.

Influence of disease-suppressive strains of Streptomyces on the native Streptomyces community in soil as determined by the analysis of cellular fatty acids.

Analysis of cellular fatty acid profiles was used to distinguish among introduced pathogen- suppressive strains and indigenous strains of Streptomyces spp. isolated from soil of field plots established to test the efficacy of Streptomyces strains PonSSII and PonR in the biological control of potato scab. Reference libraries of fatty acid profiles were developed for a collection of known pathogenic strains and the introduced suppressive strains. Population densities of pathogen-related, suppressive, and saprophytic Streptomyces strains were determined from the relationship of field isolates to mean library profiles using cluster analysis and the unweighted pair-group method using arithmetic averages. Community diversity was similarly determined. Streptomyces strains PonSSII and PonR were distinguished from each other and from the pathogen group (which clustered together) based on fatty acid profiles. The introduced, suppressive strains successfully colonized the soil and represented 2-19% of the isolates sampled over 2 years. The introduction of the suppressive strains inhibited the population of strains related to the pathogen library at each sample date; the pathogen population was substantially lower in soil from treatments where the suppressive strains were introduced compared with the nonamended control. At harvest, the pathogen-related population was suppressed 85-93 and 36-44% in 1991 and 1992, respectively, in treatments with the suppressive strains compared with the nonamended control. Diversity of the community was not affected by the introduced strains, and diversity and equitability indices were similar among treatments at any sample time. The inhibition of the pathogen-related population was correlated with a reduction of scab symptoms observed in the field plots into which the suppressive strains were introduced. Implications of a fundamental shift in the pathogen-related population in response to the introduction of the suppressive strains for long-term biological control of potato scab are encouraging.

Lasers in endoscopic gastrointestinal surgery.

Lasers have been used for endoscopic gastrointestinal surgery at our institution since 1977. The argon and Nd-YAG lasers are valuable for coagulating upper gastrointestinal hemorrhage, arteriovenous malformations, and benign and malignant lesions, as well as a variety of anatomic anomalies. Between December 1977 and September 1983, 222 procedures were performed in 122 patients. Hospital charts were reviewed and a scale constructed to assess the results of treatment. When information was available, a comparison of transfusion requirements before and after laser therapy was made. Success was achieved in 84 percent of the patients regardless of initial diagnosis. Laser therapy was not effective in 12 patients (10 percent). In 27 patients with gastrointestinal atrioventricular malformations, transfusion requirements fell from a mean of 17 +/- 5.9 units in the year before laser therapy to 1 +/- 0.8 units in the year after laser phototherapy (p less than 0.01). Complications rarely occurred (6 percent of all procedures). There were no perforations of the gastrointestinal tract and only one death (0.8 percent) partially attributable to laser application. Endoscopic laser surgery is minimally invasive and can be performed on an outpatient basis without anesthesia. It is especially valuable in patients with a high operative risk.

Neodymium yttrium aluminum garnet laser treatment of hemobilia via a percutaneous biliary catheter track.

The authors describe the use of neodymium yttrium aluminum garnet laser introduced via a percutaneous catheter track for photocoagulation of a bleeding bile duct tumor.

Supplemental nutrition and digestive disease.

Nutrition is an antegral part of medical management and patient care. The goal of nutritional therapy is to provide nutrients in form and amount appropriate to patients' needs. Dietary modification and application of available nutritional supplements in digestive disorders should be based upon an appreciation of the fundamental pathophysiological derangements and tailored to restore optimal gastrointestinal function.

Effect of nighttime anisotropine methyl bromide of duodenal ulcer healing and pain: a double-blind controlled trial.

Anisotropine methyl bromide, an anticholinergic, 80 mg given orally at 8 P.M., suppresses gastric acid secretion through the night without significant side effects. Thirty patients with endoscopy-proved symptomatic duodenal ulcer disease completed a randomized, double-blind, placebo-controlled trial of nighttime anisotropine methyl bromide therapy. Eleven (69 per cent) of 16 anisotropine methyl bromide-treated and six (43 per cent) of 14 placebo-treated subjects healed their ulcers within two weeks of starting treatment. The anisotropine methyl bromide-treated subjects averaged 0.63 +/- 0.27 (mean +/- S.E.) episodes of nocturnal pain during the treatment period versus 2.71 +/- 1.08 episodes in the placebo group (P = 0.06). This is the first reported study of this type designed to evaluate the efficacy of an anticholinergic agent in the healing of duodenal ulcers. Although not conclusive, the results suggest nighttime anisotropine methyl bromide therapy may be useful in the treatment of duodenal ulcer disease. Further studies seem warranted.