Abstract:

To make it clear that the role of fermentation products from pre-screening actinomycetes MC-15 strains in potato against late blight, the best fermentation time of MC-15 strain and the stability of antifungal products, as well as the practical control effect on potato tuber slices and detached leaves, and potato plants were investigated in laboratory and field. The results showed that the fermentation products from expansion culture 10d after seed fluid was cultured for 5d had the highest inhibition rate (95.2%), the fermentation products still had strong inhibitory rate (81.2%) after exposure for 10h under 30W UV lamp at 30 cm vertical distance, and still remained 78.67% inhibitory rate after treating with 100℃ for 60min. Its most appropriate pH was 6.0-8.0 with 92% of inhibitory rate, and could be stored at room temperature (20-24℃) for 60d with 76% of inhibition rate. After continuous passage 10 generations, the antifungal activity of fermentation products from MC-15 strain remained unchanged. On both potato tuber slices and detached leaves, the fermentation products received evident protection after inoculation with Phytophthora infestans, the relative protection rate was over 90%. It was clear that treatment of seed tuber with the fermentation products could played a significant role in both promoting growth and enhancing disease resistance of potato plants, in comparison with the control, the seedlings was early 2-4d, the average height of plants was above 3.1cm, branches was more than 1.6 , leaves was more than 2.1. And the disease index was below 21 and the relative protection reached up74%, the relative increasing yield rate was more than 30%. MC-15 strain has a great potential in practical control potato late blight in field.