Accumulated day-degrees as a measure of physiological age and the relationships with growth and yield in early potato varieties

Abstract

SUMMARYData from nine experiments from 1973 to 1981 which examined the effects of physiological age on sprout and field growth of early potato varieties are reported. Length of longest sprout per tuber and all aspects of field growth were related to number of daydegrees > 4 °C experienced by the seed after onset of sprout growth (measured as the appearance of a 3 mm sprout). It is, therefore, suggested that this scale is an effective measure of physiological age. In Home Guard and Maris Bard, increasing age of seed tubers resulted in earlier emergence and tuber initiation, larger early leaf areas and increased early tuber yields. As growth proceeded young seed produced the largest and most persistent leaf areas and the yields surpassed those of older seed and in some experiments yields decreased with increasing age at the final harvests.Optimum ages for specific harvesting periods were determined from regressions of tuber yield on age. In both varieties, they decreased with delay in harvesting. However, optimum ages differed in the two varieties and the implications for production and storage of seed and testing of varieties are discussed.

Yield formation and quality characteristics of early potatoes during a short growing period

“…The long period between planting and emergence resulted from low temperatures after planting even if pre-sprouted seed starts to grow early when soil temperatures are around +6-8°C (O'Brien et al 1983). Nitrogen fertilizer application rate did not affect duration of this period, when the transfer of nutrients from the mother tuber greatly infl uences growth of the emerging plant.…”

“…The numbers of main stems and number of tubers per hill were similar in all plots. When seed is presprouted early the numbers of stems and tubers per hill remain low and typical differences between genotypes are not evident (Varis 1973, O'Brien et al 1983. Also, within the broad range of commercial application rates the effect of nitrogen on the total number of stems and tubers is small.…”

“…Because tuber yield in a short growing season is affected mainly by the intercepted radiation, methods to increase tuber yield need to address reducing the time to emergence, improving haulm growth after emergence and increasing the harvest index. Emergence will be earlier with suffi ciently presprouted seed tubers and tubers of advanced physiological age (Varis 1973, O'Brien et al 1983, Firman et al 1992. Application of high rates of nitrogen fertilizer increases crop cover development, but may cause excessive growth of the foliage at the expense of tuber yield, resulting in low harvest index, low dry matter content and high nitrate content.…”

Impact of selenium enrichment on seed potato tubers

“…However, no analytical methods are available to predict the extent of physiological ageing. This reaction pattern has been gauged using the physiological age index (PAI) (Caldiz et al 2001), accumulated temperature sum (O'Brien et al 1983) and storage temperature sum (Struik and Wiersema 1999).…”

Influence of the thermal shock and pre-sprouting on potato tuber yield

“…However, the onset of the different developmental stages and their duration can be quite different depending on the biological characteristics of the potato variety in question, the quality of the seed tuber, climatic and soil conditions, and the agrotechnical measures employed. Some authors report that physiologically older seed tubers allow for faster emergence than their younger counterparts (Iritani, 1968;O'Brien et al, 1983), while others have found no difference (Bus and Schepers, 1978). The experiments of Van Loon (1987), however, showed that physiologically older seed tubers emerge more slowly.…”