Fungal colonization of glyphosate-treated seedlings using a new root plating technique

Abstract

A new technique for assessing the number and location of fungal colonizers of entire root systems was developed, and the effect of the herbicide glyphosate on fungal colonization of roots evaluated. Fungal colonization of roots of wheat and green bush bean seedlings grown at a 25:18 °C day:night regime took place less than 48 h after treatment of the plants with glyphosate. For both plant species grown under each of four environmental conditions (a combination of two temperatures, 17° and 25°, and two soil matric potentials, −6 and −100 kPa), Pythium spp. were the most frequent colonizers of glyphosate-treated seedlings and Fusarium spp. were the second-most frequent colonizers. Colonization of control seedlings by Pythium spp. was only observed in beans grown at 17°. In glyphosate-treated wheat seedlings, less colonization by Pythium spp. occurred at 17° than at 25°, but soil water content had no significant effect. Under low soil water content, colonization by Fusarium spp. was always higher in glyphosate-treated bean or wheat seedlings than in control seedlings, whereas this differential effect was observed only for wheat grown at 25° under higher soil moisture.