Gelling agents, silver nitrate and sequestrene iron influence adventitious shoot and callus formation from Rubus leaves

Abstract

Blackberry (Rubus spp.) cultivars Chester Thornless, Kotata, Marion, and Navaho were evaluated for morphogenic potential using the top one to four leaves from in vitro-grown shoots. In each experiment adventitious shoots were regenerated via organogenesis without an intervening callus phase. Rooting was spontaneous when shoots were transferred to a medium without growth regulators or with indole-3-butyric acid (IBA). Three gelling treatments (agar, Gelrite, and a combination) calibrated for equal gel firmness [110 g/(1.1 cm)2 π] did not affect explant regeneration or the number of shoots per explant, but did affect callus production. Significantly more callus (P≤0.05) was induced on regeneration medium (RM) with 10 μM N6-benzyladenine (BA), 0.5 μM IBA, and 0.19% Gelrite, than on medium containing either 0.71% agar, or the 0.35% agar/0.11% Gelrite combination. Explants on RM with 5 μM IBA produced significantly more callus, but fewer shoots, compared to zero or 0.5 μM IBA treatments for all gel treatments. Adding 200 mg l−1 sequestrene iron [sodium ferric ethylene diamine di-(O-hydroxyphenylacetate)] at the first transfer onto RM induced more shoots per explant than the control, but did not influence the amount of callus produced. Sequestrene iron in the second transfer on RM significantly increased the regeneration (caulogenesis) frequency from 30 to 40% for ‘Marion’ and from 23 to 43% for ‘Kotata’. Silver nitrate significantly reduced callus production for all treatments, but did not affect the frequency of caulogenesis or the number of shoots per explant.