Decline in a Tilletia indica Teliospore Population in a Naturally Infested Arizona (USA) Wheat Field

Following a 2004-outbreak of Karnal bunt in an Arizona wheat field where infection had not been detected in recent years, the population and viability of Tilletia indica teliospores in surface and subsurface layers of soil were monitored over a four-year period. The field was seeded with two parallel 1.8 m × 190 m strips of wheat, 11 m apart and the remainder planted in non-host barley. Thirty-eight 1.22 m2 wheat plots were harvested and seed examined for infection. Several times throughout each season soil samples were taken from each of 25 points throughout the field. Teliospores extracted from subsamples of each soil sample were examined to estimate the number of teliospores per gram soil and germination percentage. The average (SD) infection observed for each of the four consecutive seasons was 7.05 (4.6), 2.89 (5.5), 0, and 0.004% (0). The average number of teliospores recovered per gram of soil during the first sampling was 36 and 39 for the 0.5 cm deep (surface) and 5.5 cm deep (subsurface), respectively, with an average teliospore germination of 29%. By the last season, the average numbers of teliospores recovered were 5 and 2.5 per gram of soil, respectively, with an average germination of 1.0%.

Mrakia psychrophila sp.nov.,a new species isolated from Antarctic soil

The yeast strain （Y18） was isolated from a soil sample collected from Fildes Peninsula, Antarctica. The strain is a psychrophilic yeast with optimum and maximum growth temperatures of 10 ℃ and 18 ℃, respectively. Teliospores were formed after 7 d on malt agar, when the germination of teliospores was observed. Both inositol and D-glucuronate were assimilated. Positive results of the DBB （diazonium blue B） color reaction, urease test, and starch formation were observed. The major CoQ is Qs. All results indicated that Y18 belongs to the genes of Mrakia. The 18S rDNA sequence analyses showed that Y18 is closely related to Mrakiafrigida. DNA-DNA relatedness study, and some biochemistry characteristics indicated that Y18 represents a new species for which Mrakia psychrophila sp. nov. is proposed.

Ultrastructure and phylogeny of Ustilago coicis

Ustilago coicis causes serious smut on Coix lacryma-jobi in Dayang Town,Jinyun County,Zhejiang Province of China.In this paper,ultrastructural assessments on fungus-host interactions and teliospore development are presented,and molecular phylogenetic analyses have been done to elucidate the phylogenetic placement of the taxon.Hyphal growth within infected tissues was both intracellular and intercellular and on the surface of fungus-host interaction,and the fungal cell wall and the invaginated host plasma membrane were separated by a sheath comprising two distinct layers between the fungal cell wall and the invaginated host plasma membrane.Ornamentation development of teliospore walls was unique as they appeared to be originated from the exosporium.In addition,internal transcribed spacer(ITS) and large subunit(LSU) sequence data showed that U.coicis is closely related to Ustilago trichophora which infects grass species of the genus Echinochloa(Poaceae).