For tomatoes and more than 200 other plant species, bacterial wilt is an extremely destructive disease. Although some may not show symptoms, they keep the pathogen alive in the soil. The disease is caused by Ralstonia solanacearum, a bacterium found mainly in moist, hot areas.
The first sign of R. solanacearum is plants that start to wilt during the day and recover by nightfall. Later, they remain wilted and die. The disease usually starts in patches and spreads fairly rapidly to neighboring plants. It is almost impossible to control once it takes hold.
Fortunately for farmers, resistant genes are available. However, there are several races of R. solanacearum, with only one occurring in South Africa, namely race 1 biovar 2. It is therefore crucial to choose a tomato variety that has resistance to this race, or it will be ineffective. Varieties with the resistant gene can extend the harvest season into warmer conditions, but when the soil becomes too hot, the gene becomes less effective.
The resistant gene for race 1 biovar 2 was developed at the Agricultural Research Council station in Mbombela, and the resistant variety is named Rodade. This gene is used by other countries for our strain of the pathogen, and was hailed as a major breakthrough at the time.
Source: farmersweekly.co.za