ISHS Acta Horticulturae 808: II International Symposium on Tomato Diseases
HOW EFFECTIVE IS HYDROCHLORIC ACID TREATMENT TO CONTROL CLAVIBACTER MICHIGANENSIS SUBSP. MICHIGANENSIS CONTAMINATION IN TOMATO SEED? |
| Authors: | P.M. Pradhanang, G. Collier |
| Keywords: | bacterial canker, Cmm, acid, HCl, enzyme, seed treatment |
| Abstract:
Hydrochloric acid (HCl) treatment was tested for its effectiveness on pure Clavibacter michiganensis subsp. michiganensis (Cmm) culture, and on Cmm inoculated or naturally contaminated tomato seed. Pure cultures of Cmm did not survive in a 1% HCl solution. Further experiments were conducted on seed pre-treated with acid (1% HCl, soaked for 30 min) and on non-acid treated raw seed. Acid-treated (AT) and non-acid treated (NAT) seeds were inoculated with Cmm density ranging from 7.7 x 107 to 7.7 x 103 CFU/g. The Cmm population did not decline 12 months after inoculation on NAT seed, whereas it declined drastically on AT seed. Viable bacterium was not detectable on inoculated AT seed after one year. To determine the effectiveness of acid treatment for controlling Cmm on infested tomato seed, artificially inoculated raw seeds were treated with HCl 15 days after inoculation. Cmm did not survive in any of the treatments, indicating that Cmm is extremely unlikely to survive when dry seed is properly treated with HCl. The efficacy of HCl on naturally Cmm contaminated seed was tested using fruit which were harvested from tomato plants heavily infected with Cmm. Seeds were extracted using: 1) overnight fermentation, 2) seed washed two hours after pulping (No HCl or enzyme), 3) seed washed two hours after pulping with pectinase treatment, and 4) acid extraction (pulp soaked in an equal volume 5% HCl solution for 7 to 10 minutes followed by immediate seed wash). Cmm populations recovered from the dried seeds of these extraction methods were: 1) 7.6 x 103, 2) 6.4 x 106, 3) 6.5 x 105, and 4) 2.4 x 104 CFU/g seed respectively. Overnight fermentation of pulp was an effective treatment, but still not reliable by itself for controlling Cmm. Acid extraction did not entirely eliminate Cmm from seed. Seed lots from all extraction methods were treated with HCl to determine the effect on naturally contaminated seed. Viable Cmm was not detected in pulverized seeds of any treatment, which indicates the effectiveness of HCl to eliminate Cmm from contaminated tomato seed. | |
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