In vitro shoot organogenesis in sweet orange (Citrus sinensis L.) cv. Mosambi and the effect of ethylene adsorbents on micro-shoot quality

An improved organogenesis protocol for multiplication of sweet orange cv. Mosambi has been standardized by the use of different PGRs, basal media and ethylene adsorbents. Incorporation of cytokinins, BAP (8.8 mu M) and kinetin (6.97 mu M) resulted in best shoot organogenesis with the highest response (81.40%), no. of micro-shoots/explant (2.06), mean micro-shoot length (1.30 cm) and no. of leaves/micro-shoot (3.55) owing to complementary effect of these factors. However, the regenerated micro-shoots failed to establish due to 100% leaf abscission of micro-shoot. To retard the effect of ethylene accumulation on the regenerated micro-shoots, two types of ethylene adsorbents carrying silver ions, namely, AgNO3 and Ag2S2O3 and two gelling agents (agar-agar and Phytagel (TM)) were tested at different concentrations. Addition of AgNO3 (5.88 mu M) to the medium containing Phytagel (TM) along with cytokinin (BAP 8.8 mu M and kinetin 6.97 mu M) led to significant reduction in shoot abscission rate (4.20), while 17.66 mu M AgNO3 supplementation improved no. of micro-shoots/explants (2.19) and micro-shoot length (3.36 cm) whereas Ag2S2O3 at 20 mu M enhanced the total chlorophyll content (3.47 mg g(-1) FW) three times as compared to control. Similarly, among the tested basal media, MS basal medium induced best response on shoot organogenesis. Rooting of micro-shoots was highest (81.12%) with the supplementation of NAA (5.37 mu M), which also affected no. of roots/explant (4.52) and mean root length (5.26 cm). The supplementation of ethylene adsorbents during in vitro micro-shoot multiplication significantly improved their quality, which provides ideal rooting for development of complete plantlets in sweet orange cv. Mosambi. Key messageEthylene accumulation in glass containers inhibited micro-shoot establishment of Citrus sinensis L. Use of silver ions enhanced culture establishment and quality of the micro-shoot.