CITRUS LIMON MICROPROPAGATION: EFFECT OF DIFFERENT PHYTOHORMONES ON MULTIPLICATION AND ROOTING

Factors affecting in vitro propagation from nodal explants of mature trees of lemon cultivars were studied. Although the basal medium did not affect any variables, explants on DKW medium were greener than MS and this medium was used in the following experiments. Several combinations of BA and GA were carried out to optimize the proliferation phase. The number of shoots was dependent on the BA and GA concentration and best results were obtained with 2 mg/L BA and 2 mg/L GA. Explants length was shorter with the higher BA concentration and, in all genotypes, shoot length was higher with 2 mg/L GA. The best results for productivity (number of shoots x the average shoot length) were obtained with 2 mg/L BA and 2 mg/L GA. When BA was the only phytohormone used, proliferation was low and the shoots were short with large leaves. The transfer of in vitro shoots to rooting media, containing different concentrations of IBA and IAA, produced complete plantlets. Lemon shoots rooted well in all rooting combinations. The highest rooting percentages were obtained on a medium containing 3 mg/L IBA or IBA in combination with 1 mg/L IAA and in these media the highest numbers of roots were produced. The average root length was significantly affected by IBA and IAA concentration. Root length was greater when 3 mg/L IBA and 0 mg/L IAA were used and in this rooting medium explants showed a better appearance with greener and larger leaves. Plantlets that survived acclimatization exhibited normal growth in soil under greenhouse conditions.