1Departamento de Producción Agrícola y Animal, Universidad Autónoma Metropolitana Xochimilco, Calzada del Hueso 1100, Villa Quietud, México, D.F., Mexico.
2Instituto de Ecología, UNAM. Circuito Exterior, Ciudad Universitaria-04510, México, D.F., Mexico.
*Correspondence author: E-mail: alanaya@miranda.ecologia.unam.mxf
The in vitro effects of aqueous leachates from fresh and dry, flowering and vegetative stage of some Phaseolus vulgaris and P. coccineus varieties, alfalfa, faba bean, vetch, maize, squash, and weed species were evaluated on the same bean varieties, maize, squash, amaranth, barnyardgrass, morninglory, and purslane root growth, as well as on the growth of two Rhizobium leguminosarum biovar phaseoli strains (CPMex1 and Tlaxcala). Most of the plants were collected from the agricultural drained field (“Camellon”) in Tlaxcala, Mexico, where farmers do not use pesticides. Maize, beans, squash, alfalfa, faba-bean and vetch are intercropped or rotated in a traditional way. Significant effects of leachates from fresh (10%) vegetative and flowering cultivated plants and weeds were predominantly stimulatory. Among the species tested alfalfa and pinto bean leachates prepared from fresh shoot material were the most stimulatory (29% to 67% and 43% to 75.5% respectively). Aqueous leachates from fresh and dry (1%) cultivated legumes (vegetative and flowering) inhibited weed growth in ranges from 20% to 43% for fresh material, and 26% to 84% for dry material. In contrast, the aqueous leachates prepared from the dry shoot of most of the plants tested resulted in inhibition of root growth of the test crops (29% to 58%), except to maize. Leachates were also tested on two Rhizobium leguminosarum biovar phaseoli strains. The crop leachates stimulated the growth of both strains except those of P. coccineus var. morado that were inhibitory. Leachates from fresh shoot material of the weeds (Simsia amplexicaulis and Tradescantia crassifolia) significantly inhibited the growth of CPMex1 strain, while leachates prepared from fresh root material inhibited the growth of the Tlaxcala strain. In preliminary separation and identification tests using thin layer chromatography (TLC), phenolics were detected in dry shoot material of vegetative alfalfa, pinto bean, and vetch, and flowering faba bean. Results suggest the role of these compounds in the allelopathic effects of these legume aqueous leachates.
Allelopathy, aqueous leachates, legume crops, maize, Rhizobium, phenolics, weeds
