In vitro Selection for Resistance against Charcoal Rot Disease of Soybean [Glycine max (L.) Merrill] Caused by Macrophomina phaseolina (Tassi) Goid

Background: Soybean is an important oilseed crop. Charcoal rot caused by soil borne polyphagous fungus Macrophomina phaseolina in soybean causes about 80 percent yield loss. Methods: Callus and cell suspension cultures derived from immature and mature embryonic axis and cotyledons explants from disease susceptible soybean cultivars (cv JS335 and JS95-60) were treated with purified toxic culture filtrate generated by the fungus Macrophomina phaseolina fortified with MS culture medium. A continuous method of four cycles of selection was executed on toxic medium while during discontinuous method, a silence was given after the second and third cycle of selection using non-toxic medium. Result: The discontinuous method appeared to be superior as it permitted the calli to recover their regeneration capability. Continuous exposure to toxic culture filtrate resulted up to about 65-75 per cent mortality. A total of four lines of JS335 and nine of JS95-60 were found resistant amongst an array of putative resistant/tolerant lines during S1 generation.