Studies On Biodegradation Of Strawberry Autotoxins Phenolic Acids By Actinomyces

Autotoxicity of strawberry is one of important reasons of strawberry's continuous cropping obstacle. This study aimed at overcomeing the continuous cropping obstacles of strawberry through the degradation of strawberry autotoxins by actinomyces. Six strains of actinomyces which were isolated and screened from soil samples of Tibet Plateau were used to investigate their effects on the growth of strawberries and their ability in degrading strawberry autotoxins in liquid culture and greenhouse experiments.1. The 6 strains of actinomyces have a high ability to degrade p-hydroxybenzoic acid in liquid culture, the degradation rates of para-hydroxybenzoic acid by the 6 strains of actinomyces in the 7th culture day were 79.6%～98.7%. Act11 and Act12 could effectively degrade benzoic acid, the degradation rate of benzoic acid by Act11 in the 7th culture day was 81.2%, and which by Act12 was 86.5%. The degradation abilities of Act251, Act252, Act40 and Act49 on benzoic acid were weak. The degradation rates of benzoic acid in liquid culture by the 4 strains of actinomyces in the 7th culture day were 22.5%～58.7%.2. Both Act11 and Act12 have a high ability to degrade benzoic acid and p-hydroxybenzoic acid in soil under field conditions. After 150 days'incubation, the degradation rates of benzoic acid by Act11 and Act12 were in the range of 76.0～79.6% and 77.4～78.2%, respectively. Correspondingly, 52.1～62.3% of p-hydroxybenzoic acid was degraded by Act11 and 43.7～45.9% by Act12.3. In the greenhouse experiment, the para-hydroxybenzoic acid in the strawberry planting soil could be degraded by actimonyces 251, 252, 40 and 49 added to the soil. In the end of strawberry'life, compared to the CK treatment, the degradation rates of para-hydroxybenzoic acid were 81.5% in the soil amended with actinomyces 251, 85.1% in the one with actinomyces 252 and 90.1% in the one with actinomyces 40.4. The actinomyces 251, 252, 40 and 49 promoted the growth and tillering of strawberry roots; compared to the CK treatment, the weight of strawberry root in the 4 actinomyces treatment increased by 28.5%～50.4% and the weight of new root increased by 25.7%～80.2%. Meanwhile, the actinomyces decreased the death rate of the strawberries with relative effects of 52.3%～69.2%. The yield and sugar content of strawberry in the actinomyces treatment were little higher than in the control treatment. No significant effects were found on the total weight of strawberry plant, the areas and PPO activity of strawberry leaves.