Fraxinus nigra Marsh. (black ash) is a native North American hardwood tree species that is ecologically important and has ethnobotanical significance to American Indian communities of the eastern United States. Black ash has immature embryos at seed set, combined with complex stratification requirements, making natural regeneration difficult. This, combined with the threat and devastation being caused by the emerald ash borer, makes an in vitro adventitious shoot regeneration and rooting protocol imperative for mass propagation, conservation, and genetic improvement of this species. Hypocotyls were cultured for 4 weeks on a modified Murashige and Skoog (MS) medium containing 13.3 μM 6-benzylaminopurine (BA) and 4.5 μM thidiazuron for adventitious shoot induction. Shoots continued to regenerate when explants were then cultured on MS medium supplemented with Gamborg B5 vitamins plus 0.2 g·L−1 glycine (B5G), 6.7 μM BA, 1 μM indole-3-butryic acid (IBA), and 0.29 μM gibberellic acid (GA3) for 4 weeks, followed by transfer to MSB5G medium with 13.3 μM BA, 1 μM IBA, and 0.29 μM GA3 for shoot elongation. Once elongated, the microshoots were continuously micropropagated through nodal sectioning, and cultured on MSB5G medium supplemented with 13.3 μM BA, 1 μM IBA, 0.29 μM GA3, and 0.2 g·L−1 casein hydrolysate. Rooting of elongated microshoots was successful using woody plant medium supplemented with 4.9 μM IBA and 5.7 μM indole-3-acetic acid with a 10-day initial dark culture for root induction followed by culture under a 16-h photoperiod. Rooted plantlets were successfully acclimatized to the greenhouse with 100% survival.
Rochelle R. Beasley and Paula M. Pijut
Kaitlin J. Palla, Rochelle R. Beasley, and Paula M. Pijut
The hard, strong, very close-grained wood of common persimmon (Diospyros virginiana L.; Ebenaceae) is desirable for specialty products such as golf club heads, percussion sticks, billiard cues, and for wood turnery. The edible fruit of cultivated varieties is sold as pulp for use in puddings, cookies, cakes, and custards. Persimmon is usually propagated by grafting. Own-rooted clonal persimmon could offer several advantages to specialty fruit growers such as elimination of grafting, graft incompatibility issues, and improved rootstocks for variety testing. Four mature, grafted (male and female) persimmon genotypes and one hybrid were used for nodal explant culture. Nodal stem explants were cultured on Murashige and Skoog (MS) medium containing 10 μM zeatin, 3% (w/v) sucrose, and 0.7% (w/v) Bacto agar. Explants were routinely transferred to fresh medium every 3 weeks until shoot cultures were established. All nodal explants excised from grafted greenhouse plants produced at least one viable shoot. For in vitro rooting of microshoots, half-strength MS medium with 0, 5, 10, or 15 μM indole-3-butyric acid (IBA), 0.1 g·L−1 phloroglucinol, 3% (w/v) sucrose, and 0.7% (w/v) Bacto agar were tested with a 10-day dark culture treatment followed by culture in the light. Best rooting (14% to 87%) was achieved on medium containing 5 μM IBA for the common persimmon genotypes with means averaging from 0.5 to 3.9 roots per shoot. Ninety-one percent rooting with 5.3 ± 2.6 roots per shoot was achieved for the hybrid persimmon. Rooted plants were successfully acclimatized to the greenhouse.
Samuel G. Obae, Mark H. Brand, Bryan A. Connolly, Rochelle R. Beasley, and Stacey L. Lance
This study reports the development, characterization, and cross-species transferability of 20 genomic microsatellite markers for Aronia melanocarpa, an important nutraceutical fruit crop. The markers were developed with Illumina paired-end genomic sequencing technology using DNA from Professor Ed cultivar that was originally collected from the wild in New Hampshire. The markers were highly polymorphic and transferable to Aronia arbutifolia and Aronia prunifolia genomes. The average number of alleles per locus was 9.1, 4.5, and 5.6 for A. melanocarpa, A. arbutifolia, and A. prunifolia, respectively. The polymorphism information content (PIC) of loci ranged from 0.38 to 0.95 for all taxa, with an average of 0.80, 0.68, and 0.87 for A. melanocarpa, A. arbutifolia, and A. prunifolia, respectively. This is the first study to develop microsatellite markers in the Aronia genus. These markers will be very useful in studying the genetic diversity and population structure of wild Aronia and expediting the breeding efforts of this emerging fruit crop through marker-assisted selection.