ChileanJAR

The variation on Mn content of a suppressive and a conducive soils on the expression of take-all wheat (Triticum aestivum L.) disease, caused by the fungus Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker (Ggt), was evaluated under controlled greenhouse conditions. Two soils of the Ninth Region previously determined to be A) naturally suppressive (ultisol) and B) as conducive (andisol) to wheat take-all disease were used. Both soils were seeded with wheat cv. Dalcahue - INIA for 40 days, under natural growing conditions and in autoclave and microwave sterilized soil, to observe the effect of Mn content on the expression of the disease. The Mn content increased after sterilization from 98.2 mg kg^-1 to 293 mg kg^-1 in the suppressive soil, and from 2.5 mg kg^-1 to 295 mg kg^-1 in the conducive soil. The dry matter was not affected by the Mn variations in the soils. The root infection process of the wheat operated independently of the available Mn content of the soil, be it suppressive or conducive; and the root infection reached levels as high as 89%. The foregoing indicates that the inhibition of the infection observed on transferring 1% of the suppressive soil to a sterile base is not an expression of their manganese content but of biological factors associated with those soils.