Anna L. N. Varela ¹, Ilka M. Vasconcelos ¹, Rodolpho G. G. Silva ¹, Hudson F. N. Moura ¹, Thiago F. Martins ¹, Darcy M. F. Gondim ¹, Nagila M. P. S. Ricardo ², Francisco C. O. Freire ³, Jose T. A. Oliveira ¹

Affiliations
1 Department of Biochemistry, Science Center, Federal University of Ceara, Fortaleza- CE, 60020-181, BR
2 Department of Chemistry, Science Center, Federal University of Ceara, Fortaleza- CE, 60020-181, BR
3 Brazilian Enterprise for Agricultural Research (EMBRAPA-CNPAT), Fortaleza, Ceara, BR

Abstract

This work was conducted to assess whether or not a natural occurring polysaccharide from Adenanthera pavonina seeds (PLSAp) and its chemically sulfated derivative galactomannan (SPLSAp), which did not act as fungicides, induce defense proteins and protect a susceptible cowpea (Vigna unguiculata) genotype (BR3-Tracuateua) against the phytopathogenic fungus Colletotrichum gloeosporioides. Twelve-day-old plants were sprayed to run-off with PLSAp or SPLSAp, both at 100 and 200 mg L-1, dissolved in 0.01% Triton X-100, which served as control. The primary leaves were collected at 0, 6, 12, 24, and 48 h after the carbohydrate treatments and the activities of guaiacol peroxidase (POX), β-1,3-glucanase (βGLU), and chitinase (CHI) were determined to verify the ability of the studied galactomannans to induce alterations in their kinetics. In addition, the primary leaves of a plant group previously sprayed with SPLSAp and 6 h later inoculated with C. gloeosporioides were collected at 0, 6, 12, 24, and 48 h after the polysaccharide treatment, the enzyme activities measured, and the severity of the fungal disease evaluated. SPLSAp induced more prominently POX, βGLU, and CHI activity than PLSAp. Importantly, the combined treatment of SPLSAp and C. gloeosporioides was even more effective as enzyme inductor than SPLSAp alone, and the necrotic lesions of the anthracnose disease caused by the fungus were much less severe compared to control plants. The results indicate that SPLSAp induces plant defense proteins and increases the cowpea tolerance to C. gloeosporioides. These findings indicate that SPLSAp merits further investigation as a promising alternative or a supplemental environmentally friendly protector agent against anthracnose.

Keywords

Colletotrichum gloeosporioides, Cowpea, Defense Response, Sulfated Galactomannan, Vigna unguiculate.

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