Evaluation of the susceptibility of various grass species to <i>Gaeumannomyces graminis</i> var <i>tritici</i>

Abstract

Takeall caused by the soilborne pathogen Gaeumannomyces graminis var tritici (Ggt) is a devastating root disease of wheat As well as infected host residues from previous wheat crops grass crop or weed species also play an important role in the carryover of inoculum to the next wheat crop However the survival and spread of inoculum on different grasses differs considerably depending on their susceptibility to the pathogen Using Triticum aestivum (wheat) and Avena sativa (oat) as susceptible and resistant standards the susceptibility to Ggt of 24 grass species commonly found within wheat crops in New Zealand was examined in a simple laboratory assay Of all the grass species evaluated 83 were susceptible to Ggt with Bromus diandrus Bromus willdenowii Bromus inermis and Pennisetum clandestinum being highly susceptible while Cynosurus cristatus Cynodon dactylon and Paspalum dilatatum were highly resistant to the pathogen

Susceptibility to take-all of cereal and grass species, and their effects on pathogen inoculum

“…Amongst the herbage grasses in our field trial, only B. willdenowii had take‐all lesions on roots. Chng et al (2005) found this species almost as susceptible to Ggt as wheat in laboratory experiments.…”

“…Many grass species can be infected with Ggt under controlled conditions (Nilsson & Smith, 1981; Chng et al , 2005) but the role of grasses in maintaining or increasing Ggt inoculum under field conditions is not clear. In New Zealand, it was found that only a small proportion of wheat crops following L. perenne breaks had significant amounts of take‐all (Cromey et al , 2006).…”

“…The baiting method used was based on that of Chng et al (2005), where root segments were placed on the roots of 5–6‐day‐old wheat seedlings. After 10 days the roots of the seedlings were inspected using a binocular microscope (7× magnification) for the presence of runner hyphae and black stelar lesions.…”

“…The pathogenicity of isolates was assessed using the bioassay described by Chng et al (2005). Agar plugs (8 mm diameter) were taken from the growing edges of 7–8‐day‐old PDA cultures of each isolate.…”

Pathogenicity of <i>Gaeumannomyces graminis</i> var <i>tritici </i>increased by nitrogen applied to soil to enhance the decomposition rate of wheat residues

“…Soil cores were obtained from plots in a second-year wheat cultivar trial carried out within a commercial wheat crop. The soil had been inoculated at sowing with oat grains containing pathogenic Ggt isolates (Chng et al 2005). Consequently, the cores contained residues infected with natural and known pathogenic strains of Ggt.…”