Detection of asymptomatic fungal microorganisms in Pinus radiata tissue culture material

Abstract

Background: Tissue culture has been viewed as a relatively safe method of transporting conifer germplasm as the risk of pathogens associated with tissue cultured material has been assumed to be low. Despite these assumptions, it is unknown whether tissue cultured propagation material contains microorganisms or whether such microorganisms could grow out onto the media used. Methods: To determine whether asymptomatic tissue culture material contains fungal microorganisms, 30 different Pinus radiata D.Don genotypes from four different types of tissue culture material were analysed for the presence of fungal DNA or mycelium. In addition, thirteen fungal and oomycete isolates were cultured on standard tissue propagation media. Results: Fungal DNA was detected in all samples tested. No fungal or bacterial microorganisms were able to be grown from any of the tissue culture material tested. However, confocal microscopy showed the presence of filaments that could have been fungal mycelium. Growth of thirteen fungal and oomycete isolates on standard tissue propagation media indicated these media can severely limit the growth of some of these microorganisms. Conclusion: The results from this study show that tissue culture material does contain asymptomatic fungal microorganisms but the exact risk from these microorganisms is unclear.