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Agave tequilana is a species of great economic importance for the Mexican society. Like most agaves, it can be propagated either sexually or asexually. However, plants originating from rhizomes are mainly used for commercial production. The aim of this study was to determine the genetic fidelity of plants that were obtained from the field and propagated from rhizomes and of those propagated by in vitro culture methods (somatic embryogenesis and proliferation of axillary buds). We used an inverse ISTR (sequence-tagged repeat) molecular marker based on retrotransposon sequences to detect variability among related individual plants. Cluster analysis showed that plants could be grouped according to the propagation method employed. Plants propagated by the same in vitro method were found to be distinct from those propagated in the field. Even within each method, plants were not genetically identical. Genomic changes were evidenced not only in plants subjected to somaclonal variation in vitro but were also evident in those propagated through the natural asexual process, despite the fact that they were considered true clones. The differences observed in plants confirm the existence of asexual genetic variability.

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Uno de los principales problemas fitosanitarios son los nematodos agalladores del género <em>Meloidogyne</em>. El uso de <em>Verbesina sphaerocephala</em> podrían sustituir el uso de nematicidas químicos. El objetivo de esta investigación fue probar si extractos acuosos de <em>V. sphaerocephala</em> promueven el desarrollo y reducen los daños ocasionados por <em>M. incognita</em> en <em>Cucumis sativus</em>. Se evaluaron siete tratamientos en plantas de <em>C. sativus</em> crecidas en macetas en condiciones de invernadero: plantas testigo sin nematodos, plantas con nematodos, con nematodos + carbofuran, con nematodos + <em>Trichoderma</em>, con nematodos + extracto de <em>V. sphaerocephala</em> (concentración al 10, 15 y 20%). Se realizó tres evaluaciones para estimar altura de planta, diámetro de tallo, concentración de clorofila, número de hojas y flores, longitud y peso de raíces, índice de agallamiento, huevos en raíz y larvas en el suelo. Los resultaron mostraron que los extractos de <em>V. sphaerocephala</em> al 10 y 15% promovieron el crecimiento de las plantas y disminuyeron los índices de agallamiento de las raíces y el número de larvas de <em>M. incognita</em> en el suelo. Los extractos de <em>V. sphaerocephala</em> puede ser un potencial biológico para minimizar problemas causados por <em>M. incognita</em>.

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