The inhibitory activities of the new gossypol-free cotton variety Bukhara-9 and varieties UzFA-705 and Mirishkor were compared. It was found that Bukhara-9 and UzFA-705 had the same inhibitory activity as the resistant regionalized variety An-Bayaut-2. The inhibitory activity of Mirishkor was greater than that of variety Turon, which was developed for growing in arid zones. It was shown that Mirishkor proteinase inhibitors suppressed practically fully growth in vitro of the phytopathogenic fungus Fusarium oxysporum.