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

摘要

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 style="font-family:Verdana;font-size:12px;">Tilletia indica style="font-family:Verdana;font-size:12px;"> 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 style="font-size:10pt;font-family:""> style="font-size:10pt;font-family:""> style="font-family:Verdana;font-size:12px;">× 190 m strips of wheat, 11 m apart and the remainder planted in non-host barley. Thirty-eight 1.22 m style="font-family:Verdana;">2 style="font-family:Verdana;font-size:12px;"> 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 style="font-family:Verdana;">was style="font-family:Verdana;"> 7.05 (4.6), 2.89 (5.5), 0, and 0.004% (0). The average number of teliospores style="font-size:10pt;font-family:""> style="font-family:Verdana;">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 style="font-family:Verdana;">, style="font-family:Verdana;"> the average numbers of teliospores recovered were 5 and 2.5 per gram of soil, respectively, with an average germination of 1.0%.