Tobacco Mold And Its Biological Control In The Storage In Yunnan Province

The fungi caused tobacco mold in the storage stage were investigated in Mile, Qujing, Luxi, Lincang in Yunnan province. Thirty-eight molds were isolated from moldy tobacco, and were identified as species of Aspergillus, Penicillium, Rhizopus, Mucor, Trichoderma. The species of Aspergillus and Penicillium were dominant ones, and Aspergillus flavus var. flavus, Aspergillus fumigatus var. ellipticus, Aspergillus niger were detected in all samples.Bacteria were isolated from the tobacco leaves with good quality in the storage stage in two samples and plant rhizosphere bacterial isolates were selected to suppress Aspergillus flavus var. flavus according to its R value (R = distance from center to margin of the pathogen colony under suppression by antibiotic bacteria / radium of unsuppressed pathogen colony). An isolate B055 was demonstrated to be highly suppressive to tobacco moldy fungi in dual-culture tests on agar plates with R value 0.35. The bacterium was identified as Bacillus amyloliquefaciens.Five bacterial isolates were applied to control tobacco mold in the storage stage. Tobacco leaveswere sprayed with bacterial suspension at the concentration of 1x10 cells/ml and placed in different temperature, humility for one month. The B055 was demonstrated to be effective in controlling molds. And there were no significant variation of the general gradients such as concentrations of general sugar, general nitrogen, nicotine, protein, K+, Cl- in tobacco leaves.The isolate B055 inhibited molds growth by producing antifungal compounds. Antifungal compounds were isolated and purified by fractionation with ammonium sulphate in saturation 30%-60%. There were faint belts obtained by Tricine-SDS-PAGE. The compound was active after autoclaving at 121# for 30min and storing at about 23-26# for two months. It was insensitive to pH from 2.6 to 11.8 and UV radiation. But it produced reversible sediment at pH 4.0 to 5.2. They were further extracted with a Clg solid phase extraction (SPE), and eluted by MeOH. The 50% fraction was active. So we conferred it low molecular weight peptides.