Hayes and Garber - Cucurbit Breeding

86 BREEDING CROP PLANTS
crosses between resistant emmers and durums with susceptible
Marquis. A single rust form was used in making the artificial
epidemic. The durum-Marquis crosses were as susceptible as
Marquis in FI. Using white spring emmer as the resistant parent,
the FI was resistant, though not so resistant as the emmer parent.
Segregation for resistance and botanical characters was studied
in later generations.
for while it
Some linkage in transmission was apparent,
was quite easy to obtain resistant emmer or durum
FIG. 20. Resistance of parents and crosses to a strain of stem rust. From
left to right: Culms of resistant Durum wheat; F\ of Durum X Marquis,
susceptible;. Marquis, susceptible; F\ of Emmer, Minn. 1165 X Marquis, as
resistant as the Durum varieties; Emmer, Minn. 1165, a very resistant variety.
plants
wheats. In an examination of more than 20,000 F 3 plants, a few
it was much more difficult to obtain resistant common
with vulgar e spike
characters and resistance were obtained.
Resistant plants resembling emmer, durum, and common
wheats were also proved resistant by greenhouse inoculation
studies.
Gaines (1918, 1920) has studied the inheritance of resistance
of wheats to bunt (Tilletia tritici). It is estimated that this