Testing the efficacy of Agrigold for the control of Pectobacterium carotovorum (BD1134) isolated from potato
Mieke Daneel
ARC-Institute for Tropical and Subtropical Crops,
Private Bag X11208, Nelspruit 1200
June 2014
BlueGold Water and Chemicals
126 Johannes street
Fairland
2195
Introduction
Erwinia rot or black leg is a serious problem in the potato industry and a limited amount of effective sanitizing agents are available to control the bacterium in wash water during the packing process. Pectobacterium carotovorum can spread very fast in wash water making it even more important to find effective sanitizing agents that can kill the inoculum and prevent further spread of it. This will extend shelf life of potatoes extensively.
Aim
Tests were conducted to determine the efficacy of Agrigold in controlling Pectobacterium carotovorum (isolated from potato) development on petri dishes.
Material and Methods
Two hundred and fifty mℓ solutions, with different concentrations of Agrigold, were prepared in Erlenmeyer flasks using autoclaved water as shown in Table 1. The pH of the solutions was adjusted to about pH 6 using either HCℓ or NaOH solutions. One mℓ of a Pectobacterium bacterial suspension containing ~109 cfu per mℓ, from a Pectobacterium carotovorum culture isolated from potato and obtained from ARC-PPRI (BD1134), was then added to each flask. Serial dilutions were made from each flask after 30 min, 1 hour and 3 hours and plated on nutrient agar medium. Bacterial colony counts were made after an incubation period of one day. Each dilution was plated three times. The test was repeated three times over time under similar conditions.
Table 1 Treatment numbers, active ingredients and dosages tested.
| Treatment | Solution description | Dosage (mℓ /250 mℓ) |
| 1 | Water | – |
| 2 | 100 ppm Agrigold (AG) | 0.025 mℓ |
| 3 | 200 ppm Agrigold (AG) | 0.05 mℓ |
| 4 | 400 ppm Agrigold (AG) | 0.1 mℓ |
Results
The results of the three tests conducted can be seen in Table 2 – 4. After 30 min (Table 2) a reduction in viability of P. carotovorum of 99% or more was observed in 100 ppm, 200 ppm and 400 ppm Agrigold.
Similar results were seen after a contact time of 1 and 3 hours (Table 3 -4).
Table 2 Percentage reduction in viability of P. carotovorum after 30 minutes
| Treatment | Test 1 | Test 2 | Test 3 |
| 100 ppm AG | 99.99 | 99.19 | 99.98 |
| 200 ppm AG | 99.92 | 99.92 | 99.99 |
| 400 ppm AG | 100.00 | 99.85 | 99.99 |
Table 3 Percentage reduction in viability of P. carotovorum after one hour
| Treatment | Test 1 | Test 2 | Test 3 |
| 100 ppm AG | 99.99 | 99.91 | 99.99 |
| 200 ppm AG | 99.99 | 99.99 | 99.99 |
| 400 ppm AG | 100.00 | 99.99 | 99.99 |
Table 4 Percentage reduction in viability of P. carotovorum after three hours
| Treatment | Test 1 | Test 2 | Test 3 |
| 100 ppm AG | 99.99 | 100.00 | 99.99 |
| 200 ppm AG | 99.99 | 99.99 | 100.00 |
| 400 ppm AG | 100.00 | 99.99 | 99.99 |
Conclusion
Agrigold reduces the viability of Pectobacterium carotovorum (BD1134) significantly compared to the untreated control in the tests conducted with a contact time of 30 minutes or longer.
Agrigold can thus be described as an effective sanitizing agent killing P. carotovorum under these conditions.
Trials should be conducted to confirm these results in field and pack house conditions.