Abstract:
The filbert is propagated by layerage and a faster method is
needed to keep pace with the rapidly expanding industry and the demand
for new cultivars. Propagation by seedage and graftage were the
two methods selected for evaluation in the research. Seed experiments
were initiated to identify optimum treatments for the uniform germination
of dormant filbert seed. Grafting experiments were designed
to evaluate the effects of plant growth regulators (PGR's) and temperature
on the stimulation of cell division. Callusing trials were
established by excising bark patches and determining the effect of
PGR's and temperature on the callusing process.
Gibberellic acid (GA₃) was a potent stimulator of germination of
dormant filbert seeds. The effectiveness of GA₃ to stimulate seed
germination decreased as time of preceeding dry storage increased.
Gibberellic acid at 5 and 10 ppm was as effective as GA₃ 25 ppm in
increasing total germination. Use of low GA₃ concentrations resulted
in less injury to the epicotyl than concentrations above 25 ppm.
Imbibition of seeds in GA₃ for 6, 12, or 24 hours was effective in
significantly increasing germination over unimbibed (0-hr) seeds.
Imbibition in ethephon at 25 or 50 ppm, or vacuum infiltration of
GA₃ did not significantly increase germination compared to controls.
Increased periods of dry storage did not diminish the effectiveness
of seed stratification in germination of dormant filbert seeds.
Once dormancy was induced germination was a function of stratification.
Germination of seeds stratified 90 days at 5°C was significantly greater
than for seeds stratified only 60 days.
Filbert seed collected before normal nut drop on August 5, 12,
and 19 were capable of germination following removal of the pericarp,
but 90% of the seedlings developed growth distortions. Treatment
with GA₃ reduced the frequency of such growth distortions in these
seedlots.
Grafted filbert scions produced more parenchyma (callus) than
the stock and appeared to be more responsive to indolebutyric acid
(IBA) application than the stock. While not always statistically
significant, there was a trend towards increased tissue development
on PGR-treated sides of graft unions as compared to control-treated
sides. Application of IBA significantly increased the amounts of
parenchyma, phloem, and xylem cells of both the stock and scion at
21°C. At 15°C, only the scion responded to PGR's and the response
was much less. Gibberellic acid alone did not increase the production
of any tissue type in filbert graft unions.
Production of callus on filbert stems where patches of bark had
been removed was significantly increased by both IBA and increased
temperature.
