Regional Population Diversity of Pyricularia grisea in Arkansas and the Influence of Host Selection.

MGR586 DNA fingerprinting has been widely used to characterize population diversity of the rice blast pathogen, Pyricularia grisea. However, the frequency and distribution of particular haplotypes (individuals) within MGR-delimited lineages has not been examined in the United States. MGR586 DNA fingerprinting, mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLPs), and virulence phenotyping were used to examine genetic diversity of P. grisea in Arkansas. A total of 470 monoconidial isolates were recovered from eight rice cultivars in 18 commercial fields in nine counties in Arkansas. All isolates were examined for nuclear DNA RFLPs with the MGR586 DNA fingerprint probe, and both the MGR lineage (isolates with >80% similarity) and the haplotype frequencies were determined. Four distinct MGR586 DNA fingerprint lineages (designated A, B, C, and D) were identified among the 470 field isolates. All four lineages were found in 9 of the 18 locations. Three lineages were found in four locations, two lineages in three locations, and only a single lineage was found at two locations. In all, 10, 19, 16, and 13 haplotypes (isolates which had MGR586 DNA fingerprints which differed by 1 to 20%) were identified within lineages A, B, C, and D, respectively, among the 470 isolates examined. Within each lineage, a single haplotype (clone) predominated, representing 51 to 71% of the isolates collected for each of the four lineages. Overall, 60% of the 470 isolates belonged to one of only four haplotypes (A1, B1, C1, and D1) and these four predominant haplotypes were recovered from between 7 and 14 of the 18 locations sampled, indicating a widespread distribution of these four clones. These data indicate an exceptionally low level of genetic diversity in the regional rice blast pathogen population in Arkansas relative to several other populations of P. grisea examined from tropical environments. In addition, no mtDNA RFLPs were detected among representative haplotypes within each of the lineages, indicating a single mtDNA haplotype was present in the population. Examination of virulence indicated that two races predominated in the regional collection. All 30 isolates in lineages A and C tested had an IB-49 virulence phenotype. Out of 30 isolates in lineages B and D, 29 had an IC-17 virulence phenotype. One isolate in lineage B, isolated from a highly susceptible cultivar (L201), had an IG-1 virulence phenotype. The frequencies of the four lineages varied among the locations sampled and may have been due, in part, to the cultivar from which isolates were recovered. A single lineage was recovered from two cultivars, Mars and Millie. Although only a single field of each of these cultivars was sampled, the data indicate that certain cultivars grown in Arkansas may serve as a "bottleneck", selecting out specific lineages in the regional population. To test this hypothesis, an additional 283 isolates were recovered from replicated plots of cvs. M204 and Mars located within commercial rice fields at two locations during two seasons. All four MGR586 lineages were recovered from each location. However, there was a strong bias for lineage B on cv. M204 (79% of all isolates) and a strong bias for lineage A on cv. Mars (95% of all isolates), indicating some cultivars were effective in excluding certain lineages.

The metabolism of isamoxole in the rat and guinea-pig.

1. The absorption, metabolism and excretion of isamoxole, (2-methyl-N-butyl-N-(4-methyloxazol-2-yl)propanamide), a compound with anti-allergy properties, has been studied in the rat and guinea-pig. 2. The compound was well-absorbed by both species after oral doses of 50 to 150 mg/kg. It underwent extensive first-pass metabolism in the liver, and was excreted as a mixture of metabolites, predominantly in the urine, within 48 h. 3. Three major routes of metabolism were involved, namely deacylation, oxidative ring scission and alkyl oxidation. 4. A major plasma and urine metabolite was 1-butyl-3-(1-carboxyethyl)urea, and this was accompanied by low levels of its cyclized product 3-butyl-5-methylhydantoin.

Antianaphylactic agents. 1. 2-(Acylamino)oxazoles.

The synthesis and biological properties of 35 2-(acylamino)oxazoles are described. The majority of the compounds inhibit the release of slow-reacting substance of anaphylaxis (SRS-A) in vitro from sensitized guinea pig chopped lung. In addition, several of the compounds inhibited the release of SRS-A from passively sensitized human chopped lung and protected guinea pigs from the effects of anaphylaxis in a modified Herxheimer test.

Antiparasitic nitroimidazoles. 9. Synthesis of some 2-(4-dialkylaminomethylstyryl)-and 2-(4-amidinostyryl)5-nitro-1-vinylimidazoles.

A series of 2-styryl-5-nitro-1-vinylimidazoles carrying alkylaminomethyl or amidino functions in the 4 position of the styryl ring was prepared and evaluated for antitrypanosomal activity in mice infected with Trypanosoma rhodesiense. The alkylaminomethyl compounds were found inactive against Trypanosoma cruzi infections in mice. One compound, 2-(4-methylamidinostyryl)-5-nitro-1-vinylimidazole hydrochloride, showed antitrypanosomal activity comparable to the standard drugs suramin, pentamidine, diminazene, and melarsoprol when tested ip against T. rhodesiense infected mice and also showed some activity when tested ip against T. cruzi infected mice.

Antiparasitic nitroimidazoles. 8. Derivatives of 2-(4-formylstyryl)-5-nitro-1-vinylimidazole.

A series of 33 thioacetals and hydrazones of 2-(4-formylstyryl)-5-nitro-1-vinylimidazole was prepared and examined for antitrypanosomal properties. The thioacetals were inactive as antitrypanosomal agents but three hydrazones derived from N-aminoguanidine, pyridylacethohydrazide chloride (Girard reagent P), and dimethylaminoacetohydrazide (Girard reagent D) displayed good activity against Trypanosoma rhodesiense.