Survival of Ascochyta rabiei in chickpea residue on the Canadian prairies

Abstract

Ascochyta rabiei (teleomorph Didymella rabiei) overwinters in infested chickpea residue, which serves as a source of primary inoculum. Survival of the pathogen was assessed in studies where infested chickpea residue was maintained at the soil surface (0 cm) or buried at a 5- or 10-cm depth for up to 4 years, and in field trials at two locations where disease severity was assessed after 1, 2, and 3 years of nonhost crops. The burial studies indicate that the pathogen population increases in the year following an infected crop, and then declines over time, but that A. rabiei is still present at low levels in a field 4 years after the initial crop. However, the level of viable inoculum is low after 3 years. The field trials confirmed that the pathogen is still present following three intervening crops, but that inoculum pressure declines substantially after two intervening crops. We conclude that at least two nonhost crops are needed between successive crops of chickpea to reduce disease risk, where ascochyta blight was observed in the initial crop.

Keywords:

• Cicer arietinum
• ascochyta blight
• Didymella rabiei
• crop rotation
• tillage