Impact of cereal rotation strategies on soil inoculum concentrations and wheat takeall

The fungus Gaeumannomyces graminis var tritici (Ggt) causes takeall in cereals and survives saprophytically on crop debris during the intercrop period Commercial wheat fields with different crop rotations on 10 farms in the South Island of New Zealand were monitored over 6 years for changes in Ggt inoculum concentrations and takeall severity Takeall severity in wheat varied greatly among crop rotations across the farms with aboveground symptoms seldom visible on some farms and common on others Takeall severity was reduced by maintaining a low frequency of host crops in the rotation Ggt was detected in soil from all farms Soil inoculum concentrations were reduced proportional to the length of nonhost break crops While barley triticale and rye are less susceptible than wheat to takeall they can lead to high postharvest inoculum concentrations