CBN-V Video Archives - S2-18
Growth and Establishment of AM Fungi Glomus microcarpum var. microcarpum in Genetically transformed Roots of Cassava (Manihot esculenta Crantz)

Potty V.P.

Central Tuber Crops Research Institute, Sreekariyam, Trivandrum 695 017, Kerala , India vvpotty@ctcri.ren.nic.in

        Cassava.(Manihot esculenta Crantz) is highly susceptible and dependent on mycorrhizal fungi. Genetically modified adventitious hairy roots were induced in cassava, by infecting the plants with A4 wild type having agropine (vir) region, kanamycin resistant and hormone independent strain of Agrobacterium rhizogens. Based on the analysis of opines and GUS test, the hairy roots were proved to be transformed root clones. A living root system is a prerequisite for germination, growth and establishment of AM fungi. Transformed hairy roots were co cultured with Glomus microcarpum var. microcarpum at 25 ± 1C under a photoperiod of 14hr duration. The efficiency of the technology for mass production of AM fungi, its growth and establishment, its propensity for Border Cell (BC) production in transformed roots of cassava was studied in detail. The pre-germinated spores of Glomus microcarpum var. microcarpum infected the transformed roots in different phases. The different phases are 1) extension of germ tube, 2) attachment of germ tube, 3) formation of mycelial fan like structures, 4) formation of apprasoria, 5) formation of intercellular mycelium, septa, arbuscules and vesicles, 6) spread of infection in new roots and new regions of old roots and formation of extra cellular mycelium. The transformed root supported the growth of the AM fungi significantly better than the normal cassava root under initial growth phase, logarithmic growth phase, stationary phase where growth and infection of the AM fungus is equalized by the fast growing transformed roots and a phase of decline indicating the inadequate nutrient availability for both growing root as well as AM fungi. As BC production is related to distinct pattern of gene expression, AM fungal propensity exhibited in significant positive correlation the technology can be used for molecular level studies. At 4-5 hr light regime the AM Fungal Colonization and spore production also showed a positive correlation in transformed roots of cassava.

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