Some factors affecting the expression of the physiological age of potato seed tubers

Abstract

SummaryTwo experiments, each involving five potato cultivars, investigated the effects of date of planting and harvesting of the seed crop, and of two seed storage temperature sequences, on date of dormancy break, sprout growth and subsequent field growth. The seed storage sequences in each case involved early or late accumulation of temperature to produce a physiological age of 600 day-degrees > 4 °C.The effects of seed crop husbandry on most variables were small, with the exception of date of dormancy break, which occurred earliest when the seed crop was planted and harvested early. Effects of temperature sequence were more pronounced, although cultivars differed significantly in degree of response. Late temperature accumulation gave a larger number of sprouts per tuber, the length of the longest sprout was increased, as was the total sprout length per tuber. Emergence was more rapid, ground cover was initially greater and the number of mainstems per plant was greater with late temperature accumulation. Secondary stem production was more prolific and the total number of stems per plant greater when temperature accumulation was early. The number of tubers per plant reflected the total number of stems, and individual tuber size generally decreased as numbers increased, with the result that storage temperature treatment affected graded yields in some varieties.The field growth of the crops from the late temperature accumulation treatment was in many ways suggestive of greater physiological age than the early temperature accumulation treatment, although the number of day-degrees accumulated was the same in each case. It is possible that the number of day-degrees underestimates physiological age as the period of accumulation is delayed.