Agrobacterium rhizogenes mediated in vitro multiplication of AMF(Glomus intraradices) in Artemisia annua L.

Abstract

Arbuscular mycorrhizal fungi (AMF) are an important biofertiliser and biocontrol agent for agricultural crops. It plays an important role in phosphorous uptake and imparts stress tolerance in plants. At present, large scale multiplication of AMF is done in pots using a suitable host. However, it is difficult to maintain pure culture of AMF in pot culture. Moreover, in vitro multiplication on artificial media is not possible due to its obligate symbiotic nature.

One of the recent approaches for the mass multiplication of AMF is the Ri-T-DNA hairy root technique. AMF, if colonised on hairy roots, can be a novel technique for its in vitro mass multiplication. Hence, a study was undertaken to multiply AMF (Glomus intraradices) in the hairy roots of Artemisia annua under in vitro conditions.

The studies on the effect of G. intraradices on Artemisia confirmed root colonisation and spores in rhizosphere. Among the two strains of Agrobacterium rhizogenes used for hairy root induction in Artemisia, MTCC 532 was selected and was found to be superior to MTCC 2364. Hairy roots were induced on A. annua as per the procedure already standardised.

The cellulase enzyme (0.16 mg l-1) in water agar media enhanced G. intraradices spore germination for inoculation on hairy roots. Normal procedures carried out to infect hairy roots of Artemisia with normal and germinated spores of AMF did not yield positive results. The hairy roots failed to proliferate further and the AMF inoculum also did not survive even after repeated attempts in different culture conditions (solid, liquid static and shaking). However, the possibility of using A. annua as a host for AMF (G. intraradices) was confirmed through pot culture experiments. A. annua based inoculum was found superior to maize based inoculum and it recorded maximum survival per cent, number of leaves, plant height (cm), number of tillers, plant fresh weight and dry weight in pot culture experiment using tissue culture (TC) derived ginger plants.

The present study revealed the possibility of using A. annua as a host for multiplication of AMF. However, no root colonisation was observed on hairy roots of A. annua. Microbial contamination during AMF spore inoculation was the main limiting factor for proliferation. Thus, the procedure for in vitro inoculation of AMF spores in hairy roots of A. annua, are yet to be standardised. A suitable medium that will allow survival and proliferation of hairy roots and AMF together also needs to be standardised.