ARS | Publication request: Tilletia indica: Environmental Resiliency of Allantoid Sporidia and its Relationship to Host Infection

Submitted to: Phytopathology
Publication Type: Abstract
Publication Acceptance Date: March 13, 2008
Publication Date: July 27, 2008
Citation: Peterson, G.L., Glenn, D.L. 2008. Tilletia indica: Environmental Resiliency of Allantoid Sporidia and its Relationship to Host Infection. Phytopathology. 98:S125

Technical Abstract: Tilletia indica, causal agent of Karnal bunt of wheat, is a non-systemic bunt fungus that infects the wheat spikes at flowering via allantoid sporidia arising from basidiospores produced by germinating teliospores on the soil surface. Historically, secondary sporidia have been reported as fragile, requiring high levels of sustained moisture to survive and infect. Goates (2005) however, demonstrated in vitro, that allantoid sporidia of T. indica, as well as a number of other Tilletia species could recover from an extensive period of dehydration and low humidity. The aim of this study was to examine the significance of this discovery on the infection process. In a replicated study, blocks of wheat plants were spray inoculated with a sporidial suspension at two concentrations (2,000 or 10,000 sporidia per ml, 1.0 ml per spike). For each concentration, a group of 20 inoculated spikes were placed overnight in a dew chamber at 18C immediately after inoculation, and then returned to the greenhouse (mean 23C and 27% RH). The remaining groups of plants (20 spikes each) were placed in dew overnight at 24, 48, 120 and 336 h after inoculation. Controls plants subjected to the same treatments. At maturity, the number of infected seeds per spike was determined for each treatment. Mean (std.dev.) percent seed infection per spike was 43.42 (12.38), 26.26 (22.34), 11.29 (12.00) 3.21 (5.57), and 0, at the higher concentration and 43.87 (24.64), 33.82 (4.43), 18.38 (15.70) 8.41 (0.02), and 0.0, at the lower concentration for dry periods of 0, 24, 48, 120 and 336 h between inoculation and exposure to moisture conditions favorable for infection, respectively. These results complement the in vitro finding on the resiliency of T. indica allantoid sporidia and demonstrate an increased infection potential.