Survival of Gibberella zeae in Fusarium-damaged wheat kernels

The survival of Gibberella zeae in Fusarium-damaged kernels was investigated under field conditions at Glenlea, Morden, Portage la Prairie, and Winnipeg, Manitoba, Canada. Fusarium-damaged kernels were either left on the soil surface or buried at 5 or 10 cm and monitored for 24 months. G. zeae was isolated after 24 months from Fusarium-damaged kernels under all conditions, with isolation frequency ranging from 85 to 99% of kernels. Perithecia developed on Fusarium-damaged kernels from all locations and treatments, but ascospores developed only in perithecia on kernels located at the soil surface. A similar experiment was conducted under controlled conditions to test survival of the fungus in kernels left at the surface or buried at 5 cm in heat-treated and nontreated soil at -10, 2, and 20degreesC. The fungus survived in 76 to 100% of kernels. When kernels were incubated at 20degreesC, G. zeae was recovered from 83 and 76% of kernels in heat-treated and nontreated soil, respectively. Perithecia developed on kernels incubated at 20 and 2degreesC, but ascospores developed only in perithecia on Fusarium-damaged kernels at 20degreesC on the soil surface. As survival of G. zeae in Fusarium-damaged kernels did not decrease after 24 months, rotations of at least 2 years are necessary to avoid infection of new crops by G. zeae originating from Fusarium-damaged kernels.