A half diallel was made amongst five wheat (Triticum aestivum L.) geno
types of which one was susceptible, while the others had adult-plant r
esistance, to stripe rust (Puccinia striiformis West.). The five paren
t and ten F-1 progeny were grown in the glasshouse and were inoculated
with three rust pathotypes at the seedling stage. The latent period w
as measured on the first leaf. Two procedures were used to analyze the
half diallel. Both methods showed that the average effects of alleles
were of much greater importance than was dominance in conditioning re
sistance in response to two of the pathotypes, while for the third pat
hotype dominance was important. Resistance was conditioned by partial
dominance for two pathotypes whereas for the third it was determined b
y full dominance. Broad-sense heritabilities range from 60-73% and the
number of genes involved was different (from 1 to 4), depending on th
e pathotype.