Redroot pigweed as a host for Alternaria alternata – the causal agent of Alternaria leaf blight in potato

Abstract

The aim of the study was to establish whether the redroot pigweed (Amaranthus retroflexus L.), which is a common weed in potato crops can be a source of Alternaria alternata, the causal agent of Alternaria leaf blight, and to determine the genetic diversity of isolates of this pathogen infecting the weed and the potato cultivar tested. With the A. alternata isolates selected for genetic testing, homosporous cultures were obtained, from which DNA (deoxyribonucleic acid) was subsequently isolated. The genetic diversity of A. alternata isolates was determined by the RAPD-PCR (random amplification of polymorphic-polymerase chain reaction) method. Based on the results obtained, it was found that the dominant fungi present on the diseased leaves of both potato and pigweed plants were: Alternaria alternata, A. solani, Cladosporium cladosporioides, C. herbarum, Epicoccum purpurascens and Fusarium sambucinum. Presence of A. alternata as a dominant fungus on redroot pigweed suggests that if weed infestation is extensive, the pathogen is very likely to spread and its population to increase.