Ex vitro rooting of micro-propagated intergeneric papaya through phloroglucinol

Abstract

Micropropagation techniques of papaya have been optimized worldwide. The standard rapid multiplication
technique of papaya, which is economically viable still needs to be improved. Although establishing in vitro culture
is easy, at the same time, in vitro rooting of papaya is still very difficult. However, in vitro rooting is costly, and the
roots initiated in vitro do not have lateral branches and root hairs, making them difficult to acclimatize. Hence, the
experiments on ex vitro rooting induction of micro-propagated plantlets and acclimatization were conducted. In
vitro cultures were established using shoot tips from selected advanced intergeneric hybrid seedlings. They were
inoculated onto Murashige and Skoog (MS) medium + 3% sucrose + 1 μM BAP + 1 μM GA3 + 0.1 μM IAA + 0.25%
phytagel until plantlets were obtained. For ex-vitro rooting, plantlets were cultured with various concentrations of
phloroglucinol (PG) to investigate the appropriate rooting condition. Direct rooting of papaya micro-cutting into
potting medium (perlite + vermiculite + coco peat; in the ratio of 1:1:2) subsequent dipping into phloroglucinol
was more effective than in vitro rooting and led to 82% survival of micro-cutting during acclimatization. PG at
1000 μM was more effective than IBA in encouraging root development. The Sachet method was found to be the
most appropriate for ex vitro rooting and hardening of papaya with single-step acclimatization.