The influence of light intensity, light quality and root zone temperature on patato minituber production

[摘要] ENGLISH ABSTRACT: In South Africa the production of minitubers, as starting material for seed potatoproduction, is achieved by transplanting in vitro plantlets to a hydroponic growthmedium in the greenhouse, but current yields for minituber production are relativelylow. As commercial growers start to prefer earlier generation seed, minituberproduction systems need to be re-evaluated in order to maximize yields. The effectof light intensity, light quality and root zone temperature on the growth, tuberization,assimilate distribution, tuber size distribution and tuber dormancy of potato wasinvestigated in a series of greenhouse and glasshouse experiments.The comparison of plants grown under different light intensities indicated thatshading of 20% did not have a negative impact on the potato plants' growth, netassimilation or distribution of biomass within the plant. Higher shading levels of 40%and 50% resulted in most of the biomass being partitioned to the aboveground plantparts. The total number of tubers was not affected by light intensity but the drymatter percentage of the tubers was reduced by a decrease in the light intensity.The duration of dormancy was only determined by cultivar and tuber size.In the light quality trial, filtering some of the red light reaching the plants resulted inan increase in stem and stolon growth and a high leaf dry mass percentage, whichcan be associated with an increase in the photosynthetic efficiency associated withconditions favourable to tuberization. Tuber number and total tuber mass per plantalso increased and a high percentage of the total biomass was allocated to thetubers. Under the blue light absorbing covers stem and stolon growth also increasedbut neither the tuber number nor the total tuber mass per plant was affected. Themost distinctive effect the far-red filter had was a decrease in tuber number but anincrease in the average fresh mass per tuber.Finally, a glasshouse study was conducted with different root zone temperatures.Cooling of the root zone to below 15°C resulted in plants with a reduced height, lowerleaf-, stem- and stolon mass and reduced leaf areas. Final tuber number or yieldwas not affected, but plants were more efficient in partitioning dry matter to thetubers. The results indicated that cooling of the root medium may facilitate adecrease in stem growth without affecting tuber formation and final tuber yield.In conclusion, it can the recommended that in order to reduce excessive foliar growthdue to a large percentage of assimilates being partitioned to the haulm, minituberproducers should ensure high light intensities and cool growth medium temperatures in the greenhouse. In areas where low light intensities commonly prevail during thegrowing season, additional lighting with the incorporation of a red filter may for thisreason help to increase minituber yields.

[发布机构] Stellenbosch University