Selectivity of geraniol synthase in aromatic species to control of cotton ramulosis

Kaliny V.P. Silva1, Yrlânia L. Guerra1, Gerckson M.R. Alves2, Péricles A. Melo-Filho1, Liziane M. Lima3*, and Roseane C. Santos3
Ramulosis (Colletotrichum gossypii South var. cephalosporioides Costa) is a fungal disease of cotton (Gossypium hirsutum L.) that causes damage to leaves, stems, and bolls by reducing fiber production; it can be controlled by chemical fungicides. Geraniol is a monoterpenoid produced by some aromatic plant species whose fungicidal properties have been widely reported. Geraniol synthase (GES; EC is the precursor enzyme involved in the biosynthetic chain of geraniol. Geraniol synthase (ges) gene transcripts were prospected in 11 aromatic species with molecular and phytopathological tools to identify promising accessions for further use in in vitro and in vivo assays involving the control of cotton ramulosis. Mentha pulegium L. oil highly expressed ges and inhibited fungal growth at 1000 µL L-1 in an in vitro assay. Validation assays were carried out in two environments and M. pulegium at 2000 µL L-1 reduced the initial and final severity indices of the disease to 48% and 52%, respectively, in preventive treatments; in curative assays, indices were 44% and 54%, respectively. This indicates that it is a promising bioactive compound to control cotton ramulosis.
Keywords: Colletotrichum gossypii, Gossypium hirsutum, essential oil, fungi, monoterpene, secondary metabolites.
1Universidade Federal Rural de Pernambuco, Rua Dom Manuel de Medeiros, S/N, Dois Irmãos, CEP 52171-900, Recife, Pernambuco, Brasil.
2Universidade Estadual da Paraíba, Rua Baraúnas, 351-Universitário, CEP 58429-500, Campina Grande, Paraíba, Brasil.
3Embrapa Algodão, Rua Osvaldo Cruz, 1143, Centenário, CEP 58428-095, Campina Grande, Paraíba, Brasil.
*Corresponding author (liziane.lima@embrapa.br).