The role of seed infection in the spread of blackleg of rape in Western Australia

Abstract

A survey of rapeseed crops in Western Australia for blackleg (Leptosphaeria maculans (Desm.) Ces and de Not) infection was conducted in November 1972. No correlation between levels of pod infection in November and seed infection at maturity was established. An in vitro test showed that 67 per cent of L. maculans infected seeds gave rise to seedlings with one or both cotyledons infected. Under field conditions in 1974, a plot grown from 5.9 per cent infected seed resulted in 19.0 per cent of plants developing blackleg crown cankers, whereas a plot containing 0.08 per cent infected seed gave 1.1 per cent of plants infected. The following year at a different location, a sample assessed at 0.5 per cent infection produced only 0.06 per cent of plants with crown cankers, and, 0.08 per cent infected seed yielded 0.08 per cent infected plants.