Efficient Protocol for the In Vitro Plantlet Production of Caper (Capparis orientalis Veill.) from the East Adriatic Coast

Abstract

Caper (Capparis orientalis Veill.) is a species rich in bioactive compounds, with positive effects on human health. It has a great adaptability to harsh environments and an exceptional ability to extract water from dry soils. In Croatia, the caper grows as a wild plant, and its cultivation is insignificant, which is probably due to propagation difficulties. Micropropagation could be a solution for this. The aim of this study was to investigate the success of the micropropagation, in vitro rooting, and acclimatization of Capparis orientalis Veill. Shoot proliferation was tested in a Murashige and Skoog (MS) medium, with sucrose or glucose, and in 13 treatments, presenting the combined effect of different cytokinins and their concentrations. The success of rooting was examined in relation to the impact of various auxins, durations of rooting, and carry-over effects. A better proliferation was achieved when sucrose was used. The highest number (18) of shoots/explants was obtained in the medium supplemented with 0.6 mg·L−1 meta-topolin, while the rooting was equally efficient in the media supplemented with 2 mg·L−1 of indole-3-acetic acid or indole-3-butyric acid, or in hormone-free rooting medium. A prolonged time in the media increased the rooting efficiency, while the carry-over effect had no influence. The acclimatization rate reached 66%. Additional efforts should be made to find out how to speed upthe rooting and enhance the acclimatization rate of caper grown in Croatia.

In Vitro Rooting of Capparis spinosa L. as Affected by Genotype and by the Proliferation Method Adopted During the Multiplication Phase

“…Among the tested auxins, NAA, alone or in combination with IBA, was more effective than IBA and IAA. As far as carbon source supplemented to the rooting media is regarded, sucrose generally resulted to be more effective than fructose, confirming what suggested by other authors that sucrose should be the carbohydrate of choice for caper in vitro propagation [25].…”

“…In another Capparis species, such as C. decidua, best rooting was achieved on a medium supplemented with IBA (1 mg L −1 ) [16], but in a subsequent work of the same authors [31] 1.0 mg L −1 IBA combined with 0.5 mg L −1 IAA was considered better, whereas Deora and Shekhawat [15] found that 60-70% of the shoots rooted when pulse treated with 100 mg L −1 IBA. In another species (C. orientalis), closely related to C. spinosa, the highest rooting percentage (60%) was obtained with 1 mg L −1 of both IBA and NAA [20] and, lastly, Keresa and coworkers [25], working with wild bushes of C. orientalis, found that the rooting rate was equally efficient in the media supplemented with 2 mg L −1 of IAA or IBA, or in hormone-free rooting medium, whereas NAA at 2 mg L −1 was discarded due to the abundant callus formation on the induced roots.…”

“…Indeed, in vitro rooting is considered genotype-specific within many woody fruit species such as almond [32], pistachio [33], and peach [34], among the others. On the other hand, Keresa et al [25] evaluated in vitro caper rooting efficiency as affected by the carry-over effect and evoked the role of CKs as auxin antagonists and their involvement in tuning auxin transport and biosynthesis. Reportedly [25], BA (BAP) and its stable derivatives, are suspected to inhibit rooting, whereas meta-Topolin (mT), an aromatic natural cytokinin alternative to BA, and its derivatives do not inhibit in vitro formation, and their breakdown is relatively fast.…”

“…On the other hand, Keresa et al [25] evaluated in vitro caper rooting efficiency as affected by the carry-over effect and evoked the role of CKs as auxin antagonists and their involvement in tuning auxin transport and biosynthesis. Reportedly [25], BA (BAP) and its stable derivatives, are suspected to inhibit rooting, whereas meta-Topolin (mT), an aromatic natural cytokinin alternative to BA, and its derivatives do not inhibit in vitro formation, and their breakdown is relatively fast. Nonetheless, they did not find any significant difference in the rooting efficiency between the microshoots previously proliferated in the two different cytokinins, BAP, and mT, probably due to the very low concentration of CKs used during the proliferation phase [25].…”

“…In vitro caper propagation was reported for the first time in 1984 [13] and high rooting response was obtained by Rodriguez in 1990 [14]. Afterwards several papers have reported successful micropropagation protocols for C. spinosa and other caper related diverse species in different areas [15][16][17][18][19][20][21][22][23][24][25]. Nevertheless, although several authors have reported high success rates (80-100%) for the rooting phase, little attention has been paid to the hypothetic effect of the genotype on the results, as already claimed by Al-Mahmood [22].…”