Fungicide and germicide on contamination escaping in the in vitro propagation of Oncidium varicosum Lindl. (Orchidaceae)

Abstract

One of the greatest problem of in vitro production of seedling is the contamination of the culture medium during the micropropagation stages. This study was carried out to investigate the effect of fungicides and germicide on the plant growth and rooting, degree of phytotoxicity and control of contamination during in vitro cultivation of O. varicosum orchid. The flowers were pollinated artificially and the capsules seeds were sowed in MS culture medium modified with half of the macronutrients. The seedlings were transferred to the same culture medium uded for germination, added with the fungicides azoxystrobin, benomyl, chlorothalonil ( 0 g.L-1 , 0.1 g.L-1 ; 0.2 g.L-1 ; 0.4 g.L-1 ; 0.6 g.L-1 and 0.8 g.L-1) or sodium hypochloride with 10% active chloride ( 0 mL. L-1 , 0,5 mL.L-1 ; 0,75 mL. L-1 ; 1,00 mL. L-1 ; 1,25 mL. L-1 ; 1,50 mL. L-1). A complete randomized block design was used with ten replications per treatment and five plantlets per flask. The treatment containing 1.5 mL L-1 sodium hypochloride was the best in preventing contamination by microorganisms and did not cause any apparent harm development and in vitro rooting of Oncidium varicosum plantlets.