Abstract

The Southern Xinjiang is the main productive area of cotton, which is in long continuous cropping due to the limited land resources. The community structures of cultural fungiwere analyzed in the rhizosphere soil from healthy and diseased cotton fields. A total of236 soil fungal isolates were obtained by means of the soil plating and dilution plating method. Based on morphological characteristics and internal transcribed spacers (ITS) sequences, these fungal isolates were grouped into sixteen genera. Of these genera,Aspergillus was the dominant genus in these rhizosphere soils, followed by Fusarium. The isolates of Trichoderma species in the rhizosphere soils with healthy cotton significantly outnumbered those with diseased cotton, while the genera of Fusarium andVerticillium showed the opposite trend. The biocontrol potential of the soil fungi, especially the Trichoderma isolates, was evaluated in vitro against Fusarium oxysporum andVerticillium dahliae using the dual culture technique. The fungal isolates from different soils showed different antagonistic potential, which came mostly from Aspergillus. Moreover, 10 isolates of Trichoderma spp. were shown to have a marked inhibitory effect on the tested pathogens in vitro. All together, these data indicate that the biocontrol fungi on the plant pathogens can contribute significantly in sustaining and improving soil quality.

Key words: Continuous cropping, soil fungi, Fusarium wilt, Verticillium wilt, Trichoderma.