Resistance to pathogenic fungi and the isoflavonoids that confer such resistance capabilities were studied in two systems of wild and cultivated Phaseolus spp. seedlings. Results for P. coccineus show a gradient in isoflavonoid diversity with pathogen resistance high in wild varieties and low in cultivated ones. P. lunatus varieties showed the same trend in resistance and cyanogenic capacity, but not in isoflavonoid diversity. It is suggested that the effectiveness of the phytoalexin natural mixture depends more on its diversity than its total levels in seedlings.