The Effect of Different Storage Temperatures on the Agronomic Characteristics and Yield of Two Varieties of Potatoes

Potato (Solanum tuberosum ssp.) is an autotetraploid (2n=4x=24) species and a key member of the Solanaceae family. Physiological age is usually be determined from potato tuber initiation and afterwards. Potato seed tubers physiological preparedness for growth is an important factor in determining the productive potential of the seed potatoes. Physiological age is considered as an internal biological clock that usually covers all aspects of the production while chronological age is determined only by the length of harvest and planting time (Gregory, 1985). In most cases, the current practice for storing potato tubers is to wound-heal seed-tubers at 10-15º C during the initial l0 days of storage (Curing) and then reduce and maintain the temperature at a holding level of 4 ° C until planting while the technique of physiological aging of seed tubers, was not only one tuber storage temperature (4°C) and then transferred to a higher temperature (similar natural germination conditions), but different thermal treatments during storage conditions is used in order to increase the physiological age. Some researchers argue that thermal storage is essential to obtain quantitative and qualitative performance which its value is higher than 250 GDD. The physiological age of seed tubers 900-600 GDD in some studies to increase performance by 90 percent and was associated uniformity producing tubers..In temperate regions with spring planting date, the short growing season and high summer temperature is considered as limiting factor for potato production. For this purpose the present study was carried out to evaluate the effect of different storage temperatures on the physiological age of seed and its effect on yield and earliness of two potato cultivars.
The Effects of six different thermal treatments storage in a three-month period, including two treatments of 440 degree- day (T1 and T2), two treatments of 880 degree-day (T3 and T4), one treatment of 80 degree-day (T5), and control treatment (T6) on agronomic characteristics and yield of Marfona and Ramus cultivars was investigated by using a factorial experiment based on randomized complete block design with four replications at Kabootar Abad Agriculture Research Center of Isfahan. Period of 10 days and 12 ° C were found in all treatments. For example, in the treatment of T3, the tissue repair process that is carried out for 10 days at 12 ° C to 80 GDD is received by the tubers (8 × 10, 8 for the reason that, 4 ° C is base temperature and should be minus of 12). Salable and non-salable yield, number of stems produced, emergence rate, the number of tubers per plant, tubers weight and the tubers size were measured in this study.
The results of this study showed that the effect of temperature treatment and the interaction of temperature treatment and cultivar on yield and yield components were considered statistically significant. Marfona cultivar and use of T3 treatment with 51733 kg ha-1 had the highest tuber yield. However, there was not significant difference between this treatment and use of T2 treatment, and also using of Ramus cultivar and T3 and T4 temperature storage. For both cultivars used in this study, T3 treatment produced maximum number of stems per plant. Harvest index was fluctuated at different temperature treatments from 63.5 to 76.1 percent in the Ramos cultivar, and from 64 to 79.6 percent in Marfona cultivar. In summary, management of storage temperature can increase potato crop yields, especially in areas with short growing seasons. It seems that effects of physiological age differ between cultivars and different varieties of potatoes have different abilities to produce tuber yields in response to different heat treatments. Increasing of total tuber yield, especially as affected by thermal temperature storage application higher than 500 GDD was reported in some studies such as Knowles and Botar (1992) in which plants from 341GDD seed tubers produced 70% of their total yield as marketable, while 64% of the total yield from 900 GDD seed tubers was graded as marketable. The harvest index is a change in potatoes varieties from 9% in the wild up to 81 percent of in new cultivars, respectively. But harvest index is usually considered to be 75% for new potato varieties.
The results of this study indicated that compared with younger tubers, the yield increased from older seed tubers but it must stress that the proper seed tuber age depends upon cultivar. With using of “controlled seed-tuber aging” techniques, process of plant development was accelerating and thus tuber set and tuber enlargement faced with optimum environmental conditions. This technique can be used in the following cases: when sowing date delayed and need to quickly grow, when a farmer or a company producing seed tuber for short growing season.