Effect of crop rotation under zero tillage on soil Fusarium population

SILVESTRO L.B.; STENGLEIN S. A.; FORJAN H.; DINOLFO M.I.; ARRAMBARRI A.M.; BERÓN C.; MORENO M.V.

Mar del Plata

Congreso; VIII Congreso de Microbiología General; 2012

The presence of Fusarium species in cultivated soils is commonly associated with plant debris and plant roots, and also associated as soil saprophytes. This ability can be attributed to the capacity of Fusarium species to grow on a wide range of substrates and their efficient dispersion mechanisms. Zero-tillage and minimum tillage respond to the need to maintain and / or improve the quality of natural resources in the agricultural production process. The aim of this study was to examine the diversity of soil Fusarium spp. under different crop rotations and depths, in systems under zero tillage. Soil samples were obtained from the Barrow Experimental Station, Tres Arroyos, Buenos Aires Province, Argentina. The soil is a typical petrocalcic argiudol, Serie Tres Arroyos and the experimental design was a randomized block with three replications. Sequences consisted of five different crop rotations: I: Agricultural conservation: Wheat-Sorghum-Sunflower; II: Mixed agriculture/livestock with pastures: Wheat-Sorghum-Soybean-Canola, III: Winter agriculture in limited soils: Wheat-Canola-Barley-Soybean 2nd, IV: Traditional mixed with annual forage: Wheat-Oat/Vicia-Sunflower; V: Intensive agriculture: Wheat-Barley-Canola, Soybeans 1st and 2nd. The soil samples were taken with a hydraulic borer to a depth of 20 cm, and each one was differentiated in 0-5 cm (a), 5-10 cm (b) and 10-20 cm (c). Samples were washed and 50 soil particles of each sample were placed on Petri dishes containing potato dextrose agar (PDA 2%). The fungal colonies with Fusarium characteristics were taken and subcultured in Petri dishes with carnation leaf agar (CLA). The Fusarium species were identified by morphological characteristics and by using PCR reactions with species-specific primers. For F. solani confirmation, a part of the elongation factor 1-α (EF-1α) gene was amplified, purified and sequenced. One hundred twenty two isolates of Fusarium were obtained: F. equiseti, F. merismoides, F. oxysporum, F. scirpi, and F. solani. The most prevalent species was F. oxysporum, wich was observed in all sequences and depths. The Tukey?s test showed that the relative frequency of F. oxysporum under intensive agricultural management was higher than in mixed traditional ones. The first 5 cm of soil showed statistically significant differences respect to 5-10 cm and 10-20 cm depths. The ANOVA test for the relative frequency of F. equiseti, F. merismoides, F. scirpi and F. solani, did not show statistically significant differences. We not found significant differences in the effect of crop rotations and depth on Shannon, Simpson and species richness. Therefore we conclude that the type of crop rotation and the sampling depth did not affect the alpha diversity of the Fusarium community in this system.