Long-term effects of dryland and irrigation production systems on soil Fusarium communities in wheat

Abstract

Characterization and quantification of Fusarium communities and other microorganisms are crucial for understanding Fusarium ecology and management of root diseases of wheat. Fusarium communities in soils and on wheat roots from 12 Nebraska farms under dryland, and irrigated production systems were investigated using dilution plating assays, denaturing gradient gel electrophoresis (DGGE), and subsequent DNA sequence analysis. Results showed that the population densities of Fusarium in soils were significantly higher under dryland than irrigated production systems, and Pythium, Trichoderma, and Pseudomonas spp. in soils and on wheat roots were significantly lower in dryland systems. However, colonization of Fusarium spp. on the root surface, Shannon diversity indices and richness of Fusarium spp. in soils were generally higher in soils under dryland than irrigation systems based on the soils from 12 farms. Also, Shannon diversity indices and richness of Fusarium spp. in soils were significantly higher in soils under non-irrigated compared to adjacent irrigated centre-pivot field. Canonical correspondence analysis (CCA) showed that soil Fusarium communities generally formed two groups with overlap based on dryland and irrigation systems with 12 farm samplings, whereas the Fusarium communities formed two distinct groups in soils under irrigated and non-irrigated section of the centre pivot field. Moreover, dryland and irrigation systems affected several soil chemical properties. In general, soils under long-term irrigation tend to reduce populations and diversities of Fusarium spp. and increase populations and diversities of Pythium spp. compared with dryland systems.