Abstract:
Optimized inoculation procedures are an important consideration in achieving
repeatable plant infection when working with biotrophic rust fungi. Several plant
pathology laboratories specializing in rust research employ a system where the collection
and application of fungal spores are accomplished using an exchangeable gelatin
capsule. Urediniospores are collected from erumpent pustules on plant surfaces into
a capsule fitted to a cyclone collector controlled by a vacuum pump. By adding light
mineral oil to the same capsule, the spore suspension is then sprayed onto plants
by means of a dedicated atomizer (inoculator) connected to an air pressure source.
Although devices are not commercially available, modern day technologies provide an
opportunity to efficiently design and manufacture collectors and inoculators. Using a
process called Additive Manufacturing (AM), also known as “3D printing,” the bodies
of a collector and inoculator were digitally designed and then laser-sintered in nylon.
Depending on availability, copper or aluminum tubes were fitted to the bodies of both
devices afterward to either facilitate directed collection of spores from rust pustules on
plant surfaces or act as a siphon tube to deliver the spore suspension contained in
the capsule. No statistical differences were found between AM and metal inoculators
for spray delivery time or spore deposition per unit area. In replicated collection
and inoculation tests of wheat seedlings with urediniospore bulks or single pustule
collections of Puccinia triticina and P. graminis f. sp. tritici, the causal organisms of leaf
rust and stem rust, consistent and satisfactory infection levels were achieved. Immersing
used devices in acetone for 60 s followed by a 2 h heat treatment at 75 C produced no
contaminant infection in follow-up tests.
