In this study, 115 isolates of Fusarium oxysporum from roots of Agave tequilana Weber cv azul plants and soil in commercial plantations in western Mexico were characterized using morphological and molecular methods. Genetic analyses of monosporic isolates included restriction enzyme analysis of rDNA (ARDRA) using HaeIII and HinfI, and genetic diversity was determined using Box-PCR molecular markers. Box-PCR analysis generated 14 groups. The groups correlated highly with the geographic location of the isolate and sample type. These results demonstrate the usefulness of ARDRA and Box-PCR techniques in the molecular characterization of the Fusarium genus for the discrimination of pathogenic isolates.

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This study was conducted to know the root distribution and the effect of soil properties on root number of adult pecan trees. Two pecan trees planted to 10×10 m were selected in four orchards. Different soil conditions were present among orchards. In each tree, five trenchs were dug to 1, 2, 3, 4, and 5 m from the trunk. Root number were calculated at 30 cm increments down to 2.4 m soil depth, in each soil profile. A soil sample was taken to determine soil properties. Then the root number were correlated to the distance of the trunk, depth and soil properties. Fifty percent of roots were present in the upper layer of 90 cm. Under flood irrigation system the roots were dispersed in all space between rows and trees. The correlation coefficients (r) were significants to soil texture, organic matter (OM), pH, bulk density (BD) and micronutrient content (Cu, Fe and Mn). The r values calculated were: sand, -0.311; pH, -0.334; BD, -0.174; Clay, 0.343; silt, 0.174; OM, 0.174; Cu, 0.334; Fe, 0.114; and Mn, 0.176.