Establishment of an Efficient Micropropagation System for Humulus lupulus L. cv. Cascade and Confirmation of Genetic Uniformity of the Regenerated Plants through DNA Markers

The demand for virus-free hop planting material has increased in the last few years due to its multipurpose uses. The present study aimed to establish an effective protocol for clonal propagation of cv. Cascade using only the cytokinins as PGRs in all stages of micropropagation: (i) in vitro culture initiation using single-node micro-cuttings inoculated on modified Murashige and Skoog (MSm) medium solidified with Plant agar and supplemented with 0.5 mg L-1 6-benziyladenine (BA) with 76% recorded viability of nodal explants; (ii) in vitro multiplication of multinodal shoots on MSm medium gelled with Plant agar and supplemented with different types and concentrations of cytokinins: 2 mg L-1 kinetin (KIN), 0.7 mg L-1 1-(2-Chloro-4-pyridyl)-3-phenylurea) (1 CPPU), 2 mg L-1 meta-topoline (mT) and 0.5 mg L-1 BA, which was the best variant for shoot proliferation (9.48 & PLUSMN; 0.78 shoots/explant); (iii) rooting and acclimatization with the best results obtained by ex vitro rooting and acclimatization of plants in the same stage in perlite (96.00 & PLUSMN; 0.60% acclimatized rooted plants with 100% survival under greenhouse conditions). The true-to-type nature of in vitro raised plants with the mother plant was assessed by Random Amplified Polymorphic DNA (RAPD) and Start Codon Target Polymorphism (SCoT) molecular markers, and then their genetic uniformity were confirmed.

Automated summary

In this study, an effective protocol for clonal propagation of cv. Cascade was established using cytokinins as the only plant growth regulators. The protocol included stages of initiation, multiplication, rooting, and acclimatization. Molecular markers were used to confirm the genetic uniformity of the in vitro raised plants with the mother plant.