DEVELOPMENT OF PLANT TISSUE CULTURE PROTOCOL FOR THE PRODUCTION OF AVOCADO (Persea americana) PLANTING MATERIAL

Abstract

Avocado (Persea americana Mill.) cultivation in Sri Lanka benefits from ideal climatic conditions across various regions. However, its expansion is limited due to a shortage of planting materials. This study aimed to develop a protocol for producing avocado planting materials by refining surface sterilization for shoots of Pollock avocado variety and enhancing in vitro shoot multiplication. For surface sterilization, shoots were dipped in Thiophanate Methyl fungicide solution for 24 hours, washed with running tap water for 60 minutes, and brushed 3 times with liquid Vim detergent. They were then treated with neem oil and Tween 20, followed by immersion in 0.06% Thiophanate Methyl fungicide for one hour, 70% Ethanol for one minute, and immersed in 600 g L-1 ascorbic acid for three minutes. Finally, washed with 10% H2O2 for three minutes. The sterilized shoots were subjected to twelve different treatments with varying concentrations of 0.1% and 0.2% (w/v) AgNO3 for 15 minutes, followed by 5% and 10% (v/v) NaOCl in 5, 10, and 15 minutes of exposure in hormone-free Murashige and Skoog (MS) medium. A survival rate of 90% was recorded with 0.2% AgNO3 + 10% NaOCl in 10 minutes after three weeks. Shoot multiplication was conducted with six concentrations of 6- Benzyl aminopurine (BAP) (0, 0.5, 1, 1.5, 2, and 2.5 mg L-1) combined with 0.1 mg L-1 of Naphthalene Acetic Acid. The highest mean number of shoots (1.93±0.98), average shoot length (21.6 mm), and shooting percentage (70%) were observed in medium with 1.5 mg L-1 BAP (p<0.05). In conclusion, the Pollock variety achieved the best survival rate with 0.2% AgNO3 +10% NaOCl in 10 minutes and the best shooting was observed in MS medium with 1.5 mg L-1 BAP.