Survival of Tilletia indica Teliospores in Different Soils

Abstract

To determine the potential for Tilletia indica, cause of Karnal bunt of wheat, to survive and become established in new areas, a teliospore longevity study was initiated in Kansas, Maryland, Georgia, and Arizona. Soil from each location was infested with T. indica teliospores and placed in polyester mesh bags. The bags were placed within soil from the same location within polyvinyl chloride pipes. Pipes were buried in the respective plots such that the bags were at 5-, 10-, and 25-cm depths. Each pipe was open at the ends to allow interaction with the outside environment, however fitted with screens preventing possibility of teliospore escape. In the Karnal bunt-quarantine area of Arizona, bags of infested soil also were placed outside the pipes. Teliospore-infested soil from each location was maintained dry in a laboratory. During the first 2 years, viability declined more rapidly in pipes than outside pipes, and more rapidly in fields in Kansas and Maryland than in Georgia or Arizona. After 2 years, viability declined nearly equally. In the laboratory over 3 years, viability decreased significantly more rapidly in dry soil from Kansas or Maryland than in dry soil from Georgia or Arizona, while pure teliospores remained unchanged. We hypothesized that soils, irrespective of weather, affect teliospore longevity

Towards a more reasoned assessment of the threat to wheat crops from Tilletia indica, the cause of Karnal bunt disease

“…However, the link between survival of buried teliospores and potential distribution of Karnal bunt is unproven and tenuous. Similar longevity experiments have been undertaken in Arizona, Georgia, Kansas, Maryland and Montana and viable teliospores were recovered after burial for long periods (Babadoost et al 2004;Bonde et al 2004a, b). It is highly likely that teliospores of T. indica can survive for extended periods in soils at locations where the pathogen is never going to establish.…”

Arguments for a low risk of establishment of Karnal bunt disease of wheat in Europe

“…The percentage germination of recovered teliospores was also significantly affected by some soil sources at the end of the 32-month experimental period (Babadoost et al, 2004). A decrease in teliospore recovery and percentage germination was also noted by Bonde et al (2004a, b), who found significant differences in survival when teliospores were incubated in different soils from different regions of the US. Numbers of viable teliospores recovered from soils from Maryland and Kansas over time were much less than from soils from Arizona.…”

“…This could lead to their death and disintegration (Babadoost, Mathre, Johnston, & Bonde, 2004). A marked decrease in the percentage of extractable teliospores has been observed after 6 months (Bonde et al, 2004a). However, whether this is caused by spore breakdown, germination followed by breakdown, or the adherence of spores to soil particles during extraction has not been determined.…”

Differential expression analysis of defense-related genes responsive to Tilletia indica infection in wheat

“…Because of its international quarantine status, it has the potential for causing economic losses. Presently, 77 countries have restrictions on importing wheat from the areas where the disease occurs (Bonde et al, 2004). Being a seed-, soil-, and airborne pathogen, it is very difficult to manage once introduced to an area.…”