Banca de DEFESA: JOSÉ WELLINGTON MACÊDO VIANA

INHIBITORY EFFECT OF LEGUME LECTINS ON THE GROWTH OF PHYTOPATHOGENIC FUNGI

Fungicidal activity. Colletotrichum. Inhibition of mycelial growth. Lasiodiplodia theobromae. Legume plant lectins. Rhizoctonia solani

Lectins are natural bioactive proteins found in bacteria, fungi, animals, and plants, capable of interacting with oligosaccharides, monosaccharides, and glycoconjugates through a carbohydrate recognition domain. Plant lectins, especially those from legumes, have been extensively studied because they have various biological effects, including the ability to inhibit fungal growth. Due to their fungicidal activity and biodegradability, plant lectins can be used to control diseases caused by phytopathogenic fungi. Therefore, this work sought to evaluate the inhibitory effect of lectins from Vatairea macrocarpa (VML) and Parkia platycephala (PPL) on the growth of phytopathogenic fungi Colletotrichum okinawense, C. siamense, Lasiodiplodia theobromae and Rhizoctonia solani AG-4 HGI. Therefore, the lectins were purified by affinity chromatography, lyophilized, and tested for purity by SDS-PAGE and hemagglutinating activity. To test the inhibitory effect of lectins, fungal isolates were cultured in PDA medium containing VML (1000 μg/mL) and PPL (100 and 200 μg/mL), separately. As positive controls, pencycuron and methyl thiophanate fungicides were used. Plates containing only BDA were used as controls. The growth of C. siamense (isolate CMM 4081) reduced with the use of methyl thiophanate and PPL lectin at 200 μg/mL, without differing from each other, but differing from the other treatments. In the presence of the PPL lectin at 200 μg/mL, the growth of the L. theobromae isolate CMM 2295 was lower than that observed in the control. The VML lectin effectively reduced the mycelial growth of the L. theobromae isolate CMM 4039, similar to that observed with methyl thiophanate. The VML and PPL lectins did not show inhibitory activity on the growth of C. okinawense and R. solani. The inhibitory activity of these lectins can be species-dependent regarding Colletotrichum and isolated-dependent in relation to L. theobromae. The results encourage future research with lectins aimed at obtaining formulations to control diseases caused by fungi in post-harvest plants.