Abstract:
In this investigation levels of calcium were measured on the flag leaves of the susceptible
spring wheat cultivar Thatcher and its near-isogenic line that has Yr-18 genemediated
durable adult-plant resistance (APR ). The results showed that crystals of various
shapes were frequently present on the infected leaf areas in the spring wheat that has
the APR to stripe rust. Crystals were characterized with an energy-dispersive X-ray microanalayser
in conjunction with scanning electron microscopy (SEM). More calcium was
mobilized into infected areas of the resistance line than into the susceptible genotype. The
level of calcium in the non-infected areas of both resistant and susceptible hosts and on
the infected areas of the susceptible genotype were nearly the same. The results indicated
that calcium mobilization in the resistant near isogenic line upon infection with P. striiformis
correlated with the elicitation of a defense response conditioned by the Yr-18 gene.
This is the first report on the mobilization of calcium in a cereal-rust pathosystem as part
of a resistance response.
