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Significance

The different manifestations of potato blackleg as a disease of potato plants, seed piece decay, and storage rot all contribute to economic losses. Although the disease is now considered to be of minor importance in some potato growing regions, it continues to be a major production factor in others. Control of the disease relies wholly on crop management practices as there are no chemical control measures. Although cultivars vary in disease susceptibility, none is immune. Continued use of tissue culture-derived plantlets and minitubers (grown from plantlets in a protected environment) to initiate seed stocks coupled with limited generations of field planting are essential for minimizing the contamination of seed stocks and maintaining the level of control that has been achieved. In those areas where the disease is not adequately controlled by these measures, further research is required to determine the source from which erwinia-free planting material becomes contaminated. Whether the bacterium survives in soil or irrigation water below the detection level threshold warrants investigation. Environmental spread of bacteria from late generation crops to new seed stocks via water, wind-driven rain, or insects also needs to be studied.

Molecular research on the pectolytic erwinia, including the blackleg bacterium, has revealed many fascinating aspects concerning the genetics of pathogenicity in plant pathogenic bacteria. The complex genetic control mechanisms that modulate expression and excretion of pectolytic enzymes are now just beginning to be understood. The importance of biofilm formation and associated signaling mechanisms among bacterial cells and between bacteria and host are currently being investigated. Sequencing of the genome of the blackleg bacterium is underway and is expected to reveal even more about its ability to cause disease in potato and the mechanisms by which it does so.