May 10, 1924 
Bud Selection in the Washington Navel Orange 
523 
cember and after the oranges drop the brown spots increase in number and size. 
Plate 1, A, shows typical fruits from this limb variation and Plate 1, B, shows typical 
Thomson fruits from a normal limb on the same tree. It was first thought that 
these spots were due to fumigation burns, and when this theory was proven to 
be incorrect it was suggested that they might have been caused by hail injuries. 
The fact that the fruits on adjacent trees and those on the parent tree other than 
the ones borne by the limb variation were free from these spots indicated that 
they were not caused by hail. This conclusion has been confirmed by the fact 
that in each successive season the fruits on the limb variation have shown similar 
spots, while the fruits on the other branches have remained normal in this 
respect, and during several of these seasons no hail fell in the vicinity. 
It was thought for a time that the spotted condition of the fruit might be due 
to a fungus disease, but careful pathological studies by two independent investi¬ 
gators failed to reveal any evidence of disease. Subsequent observations and 
studies of the spotted fruits have led to the conclusion that the tissue of the 
rinds of the fruits is inherently weak and breaks down rather easily as the oranges 
approach maturity. The spots have a similar appearance to those which develop 
on citrus fruits where the oil cells have been broken and the free oil becomes 
spread over the adjacent areas of the rinds. 
The parent tree on which the second limb variation of this kind was found is a 
tree of the Washington strain of the Washington Navel orange variety, which 
had been propagated on sweet-seedling orange rootstock and planted in 1912. 
This parent tree is located in the orchard of the Lemona Heights ranch, which 
is about 3 miles distant from the Victoria orchard where the other tree showing 
this type of variation was found. 
The limb variation in the tree of the Washington strain was found to produce 
fruits which were very similar to those borne by the limb variation in the tree of 
the Thomson strain described. The fruits are smaller than those borne by the 
normal branches of the tree, more flattened in shape, and have a yellowish color 
with occasional red stripes or sections. The rinds are thicker and coarser in 
texture than is the case with the normal fruits on this tree. The fruits mature 
much earlier than those on the normal branches and drop easily, most of them 
falling to the ground during the months of November and December. The 
fruits develop small, irregular sunken brown spots on the surface of the rinds 
very similar in appearance to those found on the limb variation described above. 
None of these brown spots has been found on the reddish-colored sections which 
occur on some of the fruits. 
PROGENY PROPAGATION 
Buds secured from each of the limb variations of the two parent trees described 
above were propagated on sour orange seedlings in the spring of 1915. The 
resulting trees were planted on July 3,1917, in the orchard of the Citrus Experi¬ 
ment Station of the University of California, only two of each progeny being 
planted owing to the limited available space. In the case of the Thomson 
strain variation, the progeny test consists of two trees grown from budg 
secured from the spotted-fruit limb variation and two trees grown from buds 
taken from a normal Thomson limb. 
The progeny trees have made a healthy and normal growth and came into 
production during the 1920-21 season when they were 3 years old. All four of the 
progeny trees from the two spotted-fruit limb variations are smaller in size and 
have a more compact habit of growth than normal or typical trees of the strains. 
Plate 2 shows the comparative size and habit of growth of a progeny tree prop¬ 
agated from the spotted-fruit limb variation in the parent Thomson tree and a 
progeny tree from the normal portion of the same parent tree. 
96036—24t-3 
