Dereje Aklile Belete
Pepper (Capsicum annum L.) is an economically important vegetable and spice crops worldwide. The world pepper demand has consistently increased. However, the production of pepper has been generally low mainly due to the vulnerability of the pepper genotypes to a multitude of abiotic and biotic stresses. Propagation through seeds is restricted by short span of viability, low germination rate and requirements of extended period to produce, tissue culture provide a novel way for the asexual multiplication of pepper plants. Thus, an experiment was conducted with the main objective of this study was to determination of the combined effect of different concentration of cytokines and auxins on in-vitro shoots and root growth parameters of pepper (Capsicum annum L.) Varieties through shoot tip culture with CRD design in three replications. For shoot induction, apical shoot tips were cultured on MS medium contained 30 gm/l sucrose, 8 gm/l agar, vitamins and supplemented with three combinations (44.44 μM and 66.66 μM BAP with 2.27 μM-6.81 μM TDZ), (4.54 μM and 6.81 μM TDZ with 22.22-66.66 μM BAP) and 2.45 μM-9.8 μM of IBA combined with BAP (22.22 μM-88.88 μM) and TDZ (2.27 μM-9.08 μM) were examined. In the tested cytokinins combinations, 4.54 μM TDZ and 6.81 μM TDZ with 66.66 μM BAP for Bako local and 44.44 μM BAP with 4.54 μM TDZ and 6.81 μM TDZ for Marko fana were resulted best performance in shoot growth parameters. For the tested cytokinins to auxin combinations, 4.54 μM-6.81 μM TDZ+7.35 μM IBA for Bako local and 6.81 μM TDZ+4.9 μM IBA for Marko fana variety showed best shoot growth performance. In root induction, MS media fortified with 2.45 μM-9.8 μM IBA and 2.65 μM-10.6 μM of NAA and two combinations 7.35 μM IBA with 2.65 μM-7.95 μM NAA and 5.3 μM NAA with 2.45 μM-7.35 μM of IBA for Marko fana variety and 4.9 μM of IBA with 2.65 μM-7.95 μM NAA and 2.65 μM NAA with 2.45 μM-7.35 μM IBA for Bako local variety were examined. Among auxin combinations, 2.45 μM and 4.9 μM of IBA with 2.65 μM of NAA for Bako local and 4.9 μM of IBA with 5.3 μM of NAA and 7.35 μM of IBA with 2.65 μM of NAA for Marko fana variety were resulted best performance. Under DAS-ELISA test, three pepper viruses were detected and they were eliminated by apical shoot tip tissue culture method. In the acclimatization, the effects of PGRs and four different culture substrates on the survival of in vitro propagated pepper plantlets were examined. This result showed 81.11% and 70.10% plantlet survival for Marko fana and Bako local pepper varieties, respectively. In conclusion, it is beneficial to use the in vitro propagation protocols developed in this study for mass micro propagation and virus elimination to overcome the challenges of conventional cultivation of pepper. Further studies must focus on the performance of the in vitro propagated pepper plantlets for growth characters, yield/yield related parameters and yield quality parameters in field establishment in order to arrive at a sound conclusion.