French-bean rust (Uromyces appendiculatus) studies on resistance and determination of rust races present in New Zealand

Summary

The probable races of bean rust present in New Zealand are 10, 17, and 28, as identified in United States of America, with possibly another unidentified race which attacks the differential line “U.S. 780”.

In crosses of the resistant variety Westralia with susceptible varieties, heterozygote plants show a delayed, but definite infection with rust in field and glasshouse trials. Homozygous susceptible plants show equal susceptibility with susceptible parents. Susceptibility can thus be termed recessive or dominant according to the time of recording the disease symptoms in segregating populations.

The usefulness of this heterozygote reaction for selection in breeding material is discussed.