In vitro multiplication and microtuber production in Potato (Solanum tuberosum L.)

In vitro multiplication and micro-tuber production in potato (Solanum tuberosum L.) in three different varieties (viz., Kufri Badshah, Kufri Pukhraj and Kufri Chipsona-1) were evaluated which are grown locally and adopted by the farmers of Gujarat. Optimization of in vitro cultures were established with MS (1962) in absence of growth regulators, prior to surface sterilization with 0.1% HgCl2 for 8 minutes. Axenic cultures were evaluated for maintaining and proliferation of in vitro shoots with different levels of auxins and cytokinin. The responses of in vitro multiplication were studied with Capantothenates, CaCl2, modifications of MS (1962) in absence of vitamins and different concentrations of basal nutrients as well as different growth regulators and growth retardants. The optimum level of calcium pantothenate for in vitro shoot growth was 2.0mgl -1 . Calcium nutrtion in form of calcium chloride (CaCl2) plays important role in potato microplants. Presence of 0.1mgl -1 paclobutrazole exhibited reduction of in vitro growth of shoots which were ii thick with dark green colour. Two nodal explants favour the multiplication of in vitro shoots with liquid static cultures in the media of MS devoid of vitamins i.e. MS (ABF) + 100 mgl -1 inositol + 170 mgl -1 KH2PO4 + 0.4 mgl -1 thiamine HCl + 2.0 mgl -1 calcium pantothenate + 0.005 mgl -1 NAA + 2% sucrose. The effect of cytokinin and growth retardants on micro-tuber production were studied using different levels of BA (0, 2.5, 5.0, 7.5, 10.0 mgl -1 ) and cycocel (250, 500 and 750 mgl -1 ) under dark conditions and found maximum weight and size of microtuber in MS + 5 mgl -1 BA+500 mgl -1 CCC with 8% sucrose in solid state medium. The micro-tubers were harvested at 180 days. Different conditions for optimum development and production of in vitro microtuber were studied to know the effect of sliver nitrate, sucrose concentration i.e. levels of carbohydrate, paclobutrazole, growth retardants other than cycocel, inorganic nitrogen concentrations, different tuberisation methods as well as the effect of photoperiod and temperature were also studied. Effect of AgNO3 on microtuber production was not found effective up to the level of 10.0 mgl -1 in this study. The sucrose concentrations @ 2% and 4% were not suitable for the micro-tuber induction but the optimum level was 8% for the growth and development of micro-tuber. Effects of different vessels and paclobutrazole on shoot growth and tuberisation were evaluated and recorded that exposure of cultures to light was essential for the stimulation and initiation of microtubers. Among the iii vessels of different volume i.e. 150 ml, 250 ml and 500 ml, it 150 ml Erlenmeyer conical flask was found suitable for the micro-tuber productions. Paclobutrazole effects on microtuberization were non-significant. When compared to the propagation media in microtuber induction media (MS + 5 mgl -1 BA + 250 mgl -1 CCC + 8% sucrose) in liquid static conditions under dark positions. Axenic cultures were subcultured aseptically using single node in different tuberisation media like Direct Solid medium, Direct liquid medium, Solid-liquid bi-layer medium and Static shallow liquid-liquid systems and later was found best for weight and size of early micro-tubers. While the number of microtubers were obtained maximum in bi-layer method. Duration of microtuberisation was minimum about 70 days in MS (ABF) + 0.05 mgl -1 BA + 250 mgl -1 CCC + 8% sucrose. The nitrate concentrations significantly influenced in vitro micro tuber production which was found to be best in lower levels of nitrate. The MS (950 mgl -1 KNO3 + 825 mgl -1 NH4NO3 )+ 5 mgl -1 BA + 500 mgl -1 CCC + 8% sucrose + 0.8% Agar) was best followed by MS (475 mgl -1 KNO3 + 412 mgl -1 NH4NO3) + 5 mgl -1 BA + 250 mgl -1 CCC + 8% sucrose + 0.8% Agar concentration in media. Different culture conditions affect differentially and even varietal responses were also found different under different conditions for in vitro multiplication and microtuber production in Solanum tuberosum.