Effect of the developmental stage of potato seedlings on recovery after transplanting to the field and on tuber yield

SUMMARYUnder the short-day conditions and cool temperatures prevailing from January to March in the Nile delta, Egypt, potato (Solatium tuberosum) seedlings grown from true potato seed formed tubers in the nursery when the plants were less than 5 cm in height. In order to examine the hypothesis that slow field establishment after transplanting and low tuber yields of these seedlings were caused by premature tuberization, different treatments to delay tuberization were applied in the nursery before transplanting.Increasing the air and soil temperature in the nursery accelerated both the development of the above-ground and below-ground shoot organs, but did not improve field establishment of the seedlings after transplanting. Extension of the photoperiod with incandescent dim light, exogenous application of gibberellic acid (GA), and removal of the shoot apex to encourage the growth of lateral branches from the leaf buds increased biomass allocation to the above-ground shoot organs, decreased tuberization in the nursery and accelerated field establishment of transplanted seedlings. Extension of the photoperiod was the most effective treatment to delay tuberization, and doubled the final tuber yield from transplanted seedlings.The results are in agreement with the hypothesis that poor field establishment and low final tuber yields from potato transplants may be caused by the presence of strong tuber sinks at transplanting, which reduce assimilate partitioning towards the roots and above-ground shoots.