Improved in vitro shoot multiplication protocol of garlic (Allium sativum L.) for mass production of certified disease-free planting materials

Garlic is an important spice crop which is cultivated for its flavor and medicinal properties (antibacterial, lowers blood sugar and cholesterol, among others). It is propagated asexually at the rate of 5 to 10 per year (very low) with the threat of disease infection from generation to the next resulting to a decrease in yield and low quality bulbs. Tissue culture offers a way of producing clean and true-to-type planting materials with higher yield. A study was conducted to optimize the Plant Cell and Tissue Culture Laboratory (PCTCL) protocol for garlic shoot multiplication to increase the efficiency of shoot production and reduce production cost. Shoot tip explants of three accessions (Ilocos White, Iloilo, Batanes) were cultured using the established garlic induction medium (GIM) and four test media. The latter media contain either Schenk and Hildebrandt (SH) or Murashige and Skoog (MS) basal salts and additives and 2-isopentanyladenine (2-ip) and 6-benzylaminopurine (BAP) as growth regulators. A significant statistical difference among the test media was observed. Using the mean number of shoots, SH2 (control, SH with 2-ip, u=2.12) is significantly different from SHB (SH with BAP, u=0.92), MS with 2-ip (u=0.94) and MS with BAP (u=0.03). The highest number of shoots observed among treatments is 16 and 1 the lowest. Due to vitrification of shoots, the cultures on MS with BAP have the highest mortality rate (95%) across all accessions. Based on the number of shoots formed, there was no significant difference among accessions. The GIM is routinely used for shoot induction of explants prior to shoot multiplication. However, results showed that the cultures formed multiple shoots even without the GIM. This study confirmed that SH medium with 2-ip is the best for shoot multiplication and that the cost of production can be reduced with the deletion of the GIM step.