Micropropagation of Strawberry cv. Camarosa: Prolific Shoot Regeneration from In Vitro Shoot Tips Using Thidiazuron with N6-benzylamino-purine

An efficient micropropagation system for strawberry cv. Camarosa was developed. Sterilized runner tips were cultured on hormone-free Murashige and Skoog (MS) medium with 3% sucrose, 1 mL·L−1 Plant Preservative Mixture, and solidified using 0.25% phytagel to produce in vitro stock plants. Shoot tips derived from the in vitro stock plants were cultured on MS media containing 0, 2, 4, and 8 μM thidiazuron (TDZ) and 0, 4, 9, 18, and 27 μM N6-benzylamino-purine (BAP) for shoot induction. Shoots produced on the best shoot induction medium were rooted on MS media containing 1, 2, 3, and 5 μM of either indole-3-butyric acid (IBA) or naphthaleneacetic acid (NAA). Results showed that MS medium with 2 μM TDZ and 4 μM BAP was optimum for shoot multiplication from the shoot tips. The most suitable medium for inducing the highest number of roots per explant, the highest percentage of explant with roots, and the highest mean root length were 1 μM NAA, 1 μM IBA, and hormone-free MS medium, respectively. Plantlets were transplanted into substrate consisting of perlite + vermiculite + cocopeat (2:1:2 v/v/v) resulting in 90% survival. After 1 month, plants were irrigated using Hoagland's solution and runners were produced after 3 months.

Long-term in Vitro Regeneration of Hamelia patens

This report describes an efficient in vitro regeneration protocol for H. patens (firebush), a heat-tolerant ornamental shrub native to tropical and subtropical America. Shoot cultures were initially established using shoot tips placed on MS-revised medium containing 2.3 μM 2,4-D, 2.3 μM kinetin, and 0.25% polyvinylpyrrolidone. Other types of explants (nodal and internodal segments, leaf pieces, floral buds) did not regenerate shoots when placed on this medium. Two-month-old plantlets derived from the shoot tips were subcultured on MS medium supplemented with 0.5 μM thidiazuron (TDZ), and within 3 to 4 weeks, some callus was produced at the root–shoot junction. When this callus, with a small portion of the root and shoots, was placed on MS medium with 0.05 μM TDZ and 0.01 μM ABA, prolific shoot formation occurred within 3 to 4 weeks followed by root formation. By regular subculturing every 5 to 6 weeks, hundreds of plantlets have been obtained over the past 3 years with no apparent decline in regeneration potential. Addition of activated charcoal (0.5%) to the culture medium has greatly improved growth of the plantlets.

The Sensitivity of Young White Spruce to Spruce Budworm Defoliation

Relationships between defoliation and volume growth were determined for 68 young white spruce trees in a 20-year-old plantation defoliated over a 2-year period by the spruce budworm. In the first year of defoliation, intensities ranging from 7 to 89% of the current foliage did not influence volume growth significantly. Two consecutive years of defoliation, averaging over the 2-year period from 0-33, 34-66, and 67-100% of the current foliage, reduced average volume growth by about 6, 11, and 27%, respectively. White spruce is much less sensitive to defoliation than balsam fir. This is partly due to white spruce's ability to compensate for even moderate defoliation intensities by a prolific shoot production. North. J. Appl. For. 8(4):168-171.