Absence of lateral transfer within the oat leaf of substances responsible for crown rust resistance

Abstract

The longitudinal half of each of three inoculated leaves of an unusual trisomic oat seedling was resistant and the other half susceptible to crown rust race 264. Resistance was conditioned by the Pc-15 gene located on the extra M4 chromosome. It is postulated that the chimera resulted early in the ontogeny of the plant and one of the cells which eventually developed into the susceptible half of the plant failed to receive or lost its M4 chromosome. The chimera demonstrates that the factors responsible for crown rust resistance are not mobile, in a lateral direction, within the leaf.