Authors: Etienne Yergeau Vladimir Vujanovic Marc StArnaud
Publish Date: 2006/05/18
Volume: 52, Issue: 1, Pages: 104-113
Abstract
Asparagus Asparagus officinalis is a highvalue perennial vegetable crop that has shown a marked decline in productivity after many years of continuous harvesting This decline is caused by an increase in both abiotic autotoxicity harvesting pressure and biotic stresses fungal infections mainly Fusarium crown and root rot FCRR To gain insight into disease development and possible mitigation strategies we studied the effects of harvesting time in the growing season and field age on FCRR development Fusarium species composition and arbuscular mycorrhizal fungi AMF communities in both a controlled field experiment and an ecological survey of commercial fields In one experiment a 3yearold asparagus field was subdivided into plots that were harvested or not and sampled throughout the growing season to assess shortterm dominant Fusarium species shifts In addition diseased and healthy asparagus plants sampled from six commercial fields in the same geographical region were used to assess Fusarium and AMF communities in relation to different parameters Fusarium and AMF communities were described by using a polymerase chain reaction PCR–denaturing gradient gel electrophoresis DGGE approach and results were analyzed by mainly correspondence analysis and canonical correspondence analysis Results showed that dominant Fusarium taxa assemblages changed throughout the growing season Harvested plots had significantly more FCRR symptomatic plants at the end of the growing season but this effect was not related with any trend in Fusarium community structure Sampling site and plant age significantly influenced AMF community structure whereas only sampling site consistently influenced the Fusarium community Diseased and healthy plants harbored similar Fusarium and AMF communities Shifts in Fusarium community might not be responsible for different disease incidence because they are ubiquitous regardless of plant health status or harvesting regime The different incidence noted might rather be related to plant physiology antagonist microbial communities or soil parametersThis work was supported by an NSERC grant to M StArnaud and a CORPAQPAR team grant Financial assistance to E Yergeau was provided by an FQRNT postgraduate scholarship S Daigle is thanked for multiple correspondence frequency table analysis and principal component analysis We are also indebted to S Roy M Cormier and G Champagne for letting us sample their fields and to DW Sommerville for help in the fieldwork GA Kowalchuk is gratefully acknowledged for insightful comments on this manuscript
Keywords: