ARS | Publication request: Longevity of secondary sporidia of floret infecting Tilletia species in lab and field environments.

Submitted to: Journal of Plant Pathology
Publication Type: Abstract
Publication Acceptance Date: February 13, 2008
Publication Date: August 1, 2008
Citation: Goates, B. 2008. Longevity of secondary sporidia of floret infecting Tilletia species in lab and field environments.. Journal of Plant Pathology.90:S2.160

Technical Abstract: B.J. Goates USDA-ARS, 1691 S. 2700 W. Aberdeen, Idaho 83210, USA Email: bgoates@uidaho.edu Forcibly discharged air-borne secondary sporidia resulting from germinating teliospores of Tilletia horrida, T. indica, and T. walkeri initiate local infection of florets and cause the diseases rice smut, Karnal bunt of wheat, and rye grass bunt respectively. Secondary sporidia are considered to be fragile and short lived, and to require very high humidity to survive longer than a few hours. To examine this, secondary sporidia of these species originating from PDA and WA cultures were deposited onto petri dish lids via natural liberation and were air dried and maintained at 10-20% RH at 20-22° C, and at 40-50% RH at 18° C. After various time periods lids were inverted over PDA to determine if sporidia could regenerate. Regeneration occurred after up to 30 days at 10-20% RH and 60 days at 40-50% RH. Sporidia commonly regenerated and had produced new secondary sporidia with extensive hyphae 18 hours after lids with dried sporidia were inverted over PDA. Sporidia initially dried rapidly at 10% RH or dried over 10 hours had no difference in viability. In field experiments, sporidia of T. horrida and T. indica on petri dish lids placed 20-25 cm from the soil surface in wheat and barley fields for up to 46-49 days rapidly regenerated, even after several diurnal periods that included temperatures above 38° C and relative humidity below 10%. It appears sporidia can survive for extensive dry periods in common field environments and then rapidly regenerate and infect plants under humid rainy conditions associated with the diseases.