Perpetuation of Bacteria
The Phytopathogenic bacteria do not produce any resting structures. They survive by some of the following ways:
1. Survival on Self Sown Plant, Collateral Hosts:
Bacterial pathogen survives and multiplies on self sown plants of host crop, collateral hosts during the main and the off seasons. The collateral hosts are most often perennial or noxious weeds growing in the host crop fields, or in their vicinity while others may be cultivated economic crop plants. The host range of some bacterial plant pathogens is very wide.
E. g Pseudomonas solaneceanum -200 host plants.
Agrobacterium tumefaciens- 150 host plants.
2. Survival on Host Crop:
The pathogens of the bacterial leaf blight and the leaf streak of rice may survive from crop to crop in double or triple – rice culture areas in the tropics. The latent infections as in cankers, galls, bud scales, the cracks in the bark or sheltered place are often further protected by the host mucilage in trees as in the citrus canker or the fire blight.
3. Survival on Non Host Plants:
Xanthomonas campestris pv. Citri causal agent of citrus canker has been found to survive in the non-host plants. The epiphytic (Saprophytic) existence of X.campestris pv . phasebli on the phyllosphere of Phaseolus vulgaris has been found.
4. Survival through Crop Residues and in Soil:
Some of the Phytopathogenic bacteria are capable of living saprophytically on plant residues or parennate in the soil in Free State or on any organic matter. E.g Erwinia spp. Pseudomonas, solanacearum racee2, Xanthomoans campestris pv. malvacearum. Most of the bacterial pathogens of aerial parts can not survive in a natural soil for a long time due to their poor competitive saprophytic ability and antagonism of other microorganisms.
5. Survival through Seeds and Vegetative Propagation Parts:
Some of the phyopathogenic bacteria survive in seeds of some crops and vegetative plant parts used for propagation E. g Xanthomonas campestris pv. oyzae and Xanthomonas compestris pv. malvacearum survive through seeds. Pseudomonas solanacearum survive in potato tubers.