Soil amendments and watering influence the incidence of endophytic fungi in Amaranthus hybridus in South Africa

A study was conducted to determine the influence of soil amendments and irrigation on the incidence of endophytic fungi in Amaranthus hybridus. Five- and 6-month-old, asymptomatic tissues from A. hybridus were sampled from cultivated plots at Potchefstroom, South Africa in 1997 and 1998, respectively. Soil treatments consisted of the addition of commercial fertilizer or manure to irrigated soils, and wood ash to nonirrigated soils; control plots were neither amended nor irrigated. Ten leaves, 10 petioles, and 10 roots from each of five plants per soil treatment were surface disinfested and small sections from each were placed on corn-meal agar (8000 isolation attempts). After 5 days, the resulting fungal colonies were counted. Significant differences in recovery of fungi occurred among the soil treatments (P < 0.01) and among plant parts (P < 0.01). The highest recovery occurred from the commercial fertilizer and watered treatment (least stressed) for leaves and petioles in both years. Higher fungal recovery also occurred in the wettest year from leaves and petioles for all soil treatments. In contrast, roots yielded higher fungal recovery in the driest year for all soil treatments. These results show that soil attributes can influence frequency of endophytic fungi in both above- and below-ground tissues.