Application of viability‐qPCR to assess survival of Cladosporium cladosporioides H39 and Lysobacter enzymogenes 3.1T8 in slurries used for seed coating

Seed coating technologies are used to cover seeds with external materials including propagules of microbial biological control agents (MBCA). Protection of MBCA during seed processing and handling is essential to achieve long shelf-life of coated MBCA. The viability of MBCA added to slurries prepared before use for seed coating should thus not be affected. The survival of Cladosporium cladosporioides H39 and Lysobacter enzymogenes 3.1T8 in slurries provided by seed companies was quantified by previously designed strain-specific viability‐qPCR assays. The effects of storage temperature and storage duration of slurries on survival of the added microorganisms were also quantified. Viability of added inocula decreased by more than 90% within a few days in most slurries, even if stored at low temperature (5°C). However, for certain slurry-MBCA combinations, reduction in viability was less than 90% during the initial days of storage. Selection of MBCA with long shelf-life on coated seeds and adaptations of seed processing technologies to protect MBCA during seed processing and handling are essential for a change from chemical to biological seed treatments for control of seedling diseases.