Acclimatization of micropropagated mature avocado

J.C.A. Hiti Bandaralage, A. Hayward, C. O¿Brien, C. Beveridge, N. Mitter
The morphology, anatomy and physiology of in vitro cultured plants do not facilitate survival when transferred to dynamic ex vitro environments. The benefits of a micropropagation system completely depend on successful transfer of in vitro plants to septic ex vitro conditions. Avocado (Persea americana Mill.) is a luxurious tropical fruit becoming very popular with increasing consumption around the globe due to its high nutritional value. It is a “micropropagation worthy” plant species, to meet the high industry demand for clonal propagules. Being a woody perennial, in the category of recalcitrant species for micropropagation, avocado has consistently proven to be very difficult to induce roots in vitro. Even if rooted, plant survival during acclimatization is very poor due to few, mostly unbranched roots produced at the rooting stage. The current study focused on optimising the last stage of the micropropagation process; acclimatization of in vitro regenerated avocado plantlets to achieve higher survival rates. The methods tested included mist spray application, root soaking treatments and a new method where plants were acclimatized in the tissue culture jar itself. The mist spray durations tested (1, 2 and 3 days) produced similar results. Highest survival rate was 74% with 3 days mist spray. Root soaking treatments and the duration of humidity dome-cover positively influenced plant survival. Root soaking for 2-3 days followed by a 4-week dome-cover period gave very high survival of 97%. The method of acclimatizing plantlets in the tissue culture jar with lids open (under a dome cover for 2 weeks followed by no dome cover for 2 weeks) also resulted in 96% survival of plantlets even after 24 weeks under glasshouse conditions. The optimised acclimatization methods are convenient and expected to be effective on large scale. The methods will likely be transferrable to other woody species encountering similar problems as avocado during acclimatization.
Hiti Bandaralage, J.C.A., Hayward, A., O¿Brien, C., Beveridge, C. and Mitter, N. (2018). Acclimatization of micropropagated mature avocado. Acta Hortic. 1224, 13-20
DOI: 10.17660/ActaHortic.2018.1224.3
avocado, acclimatization, micropropagation

Acta Horticulturae