Micropropagation of guava (Psidium guajava']java L.)

Guava (Psidium guajava L.) is difficult to propagate using conventional asexual techniques, with most growers using seedling planting stock. However, these seedlings are highly variable. We therefore developed an in vitro technique to clonally propagate guava. Various concentrations of BAP (6-benzylaminopurine) and TDZ (thidiazuron) were used to regenerate and micropropagate plants. Two explant sources were compared: greenhouse grown plants (GHRP) and in vitro-harvested axillary buds (IVDS). GHRP with BAP at 2 mg 1(-1) gave 3.7 shoots per single node cutting with an average length of 0.7 cm. Shoots 3.0 cm long were obtained with 0.5 mg 1(-1) BAP, however only 2.1 shoots per explant were produced. For IVDS, the largest number of shoots (3.9 per explant) was obtained with BAP at 0.25 mg 1(-1), with an average shoot length of 1.6 cm. Generally, lower concentrations of BAP gave fewer but longer shoots. The highest number of roots and longest roots per shoot (5.4 and 2.0 cm, respectively) were obtained with 1 mg 1(-1) indole-3-butyric acid (IBA). A protocol for producing clonal plants over eight weeks is described.