Protocol optimization for in vitro clonal propagation of jackfruit (Artocarpus heterophyllus L.)

Abstract

Jackfruit (Artocarpus heterophyllus L.) is a cross pollinated fruit tree valued mainly for its fruit and timber wood. Although the crop has been introduced to Ethiopia and adapted well to the Jimma area, its potential for production has not been exploited due to the absence of an efficient method for large scale planting material propagation. Jackfruit is commonly propagated through seed but being cross pollinated and highly heterozygous, it doesn’t bear fruits that are true to type. Furthermore, the seed loose viability in a short period of time. Other vegetative propagation methods are generally cumbersome and highly season dependent, making it difficult for commercial level propagation. Thus micropropagation is an alternative method for production of large number of genetically uniform planting materials with desired characteristics. The present study was initiated to optimize a protocol for in vitro clonal propagation of jackfruit. In this study, three experiments were carried out: the sterilization experiment, the in vitro shoot multiplication and rooting. For the surface sterilization experiment, two sterilants viz., HgCl2 and local bleach (Berekina™) were tested separately at three concentrations with three time durations. For the in vitro shoot multiplication, the combination effects of four levels of each of BAP and NAA were tested. For the rooting experiment, the combination effects of three levels of each of IBA and NAA were evaluated both on half concentrated MS salts (half MS) and full concentrated MS salts (full MS). Ex vitro rooting was also done after dipping the basal ends of the micro shoots in 1g/l of each of IBA, NAA and IAA prior to planting on a mixture of top soil, sand and cow dung in 1:1:1 proportion.The results showed that explants surfacesterilized with 0.1% HgCl2for 5 minutes gave the maximum (93.33%) healthy shoots with no shoot death. For the explants sterilized with Berekina™ (containing 5.25% active chlorine), the maximum (86.67%) healthy shoots were obtained on 25% Berekina™ for 15 minutes with no shoot death.With regards to the in vitro shoot multiplication, the combination of BAP and NAA resulted in significant (P<0.01) differences for shoot number, shoot length and leaf number; where by 2mg/l BAP alone was found to be the best with a mean shoot number of 5.12 and length of 0.89 cm.For the rooting experiment, none of the micro shoots in both in vitro and ex vitro conditions showed root development. From this, it could be inferred that 0.1% HgCl2for 5 min is optimum to obtain contamination free shoots with little or no shoot death and 2mg/l BAP is optimum for best shooting. Therefore; the optimized protocol could be used as a baseline for further studies on in vitropropagation of jackfruit and for rooting, growth regulator combinations could be varied to obtain roots for a successful micropropagation.