Effective seed sterilization methods require optimization across maize genotypes

Studies of plant-microbe interactions using synthetic microbial
communities (SynComs) often require the removal of seed-associated
microbes by seed sterilization before inoculation to provide gnotobiotic
growth conditions. A diversity of seed sterilization protocols have been
developed in the past and have been used on different plant species with
various amounts of validation. From these studies, it has become clear
that each plant species requires its own optimized sterilization protocol.
It has, however, so far not been tested if the same protocol works equally
well for different varieties and seed sources of one plant species. We
evaluated six seed sterilization protocols on two different varieties
(Sugar Bun & B73) of maize. All unsterilized maize seeds showed
fungal growth upon germination on filter paper, highlighting the need for
a sterilization protocol. A short sterilization protocol with hypochlorite
and ethanol was sufficient to prevent fungal growth on Sugar Bun
germinants, however, a longer protocol with heat treatment and germination
in fungicide was needed to obtain clean B73 germinants. This difference
may have arisen from the effect of either genotype or seed source. We then
tested the protocol that performed best for B73 on three additional maize
genotypes from four sources. Seed germination rates and fungal
contamination levels varied widely by genotype and geographic source of
seeds. Our study shows that consideration of both variety and seed source
is important when optimizing sterilization protocols and highlights the
importance of including seed source information in plant-microbe
interaction studies that use sterilized seeds.