Simple and efficient method for detection and identification of Pyrenochaeta terrestris on maize root

Abstract

The present study describes the developed filter layer method for the consistent determination and identification of the natural occurrence of Pyrenochaeta terrestris in maize roots. The field experiment was set up to establish the applicability, accuracy and efficiency of this method for the pathogen isolation from roots of maize grown under different agroecological conditions. According to this method, the 10- to 15-mm long tissue sections, mainly cut at the margin of lesions developed in roots, were placed on two layers of moisten filter paper in Petri dishes and incubated for 6-7 days under laboratory conditions, 25 +/- 2 degrees C and daylight. The unique reddish-purple (beet-red) pigmentation was used as an indicator of the fungal incidence in infected roots, which facilitated a succeeding confirmation of the pathogen on PDA at 25 degrees C in the dark and on CLA in the alternating 12 h light (fluorescent and near-ultraviolet light)/12 h dark conditions. Obtained results showed that the filter layer method was very effective for the P. terrestris detection and that it could be applied for a rapid assessment of response of maize genotypes, environmental and seasonal effects on the fungal growth on roots and the fungal distribution. Advantages of this method for the detection and quantification of P. terrestris in relation to the methods described in the literature include: a) low investments, because many root samples can be tested immediately at the same time; b) results can be obtained rapidly (6-7 days after sampling); and c) minimal interference by other fungi or bacteria.