Physiological and biochemical justification of second-crop potatoes (Solanum tuberosum L.)

The relevance of the conducted studies lies in the need to improve the technology of growing potatoes from freshly picked tubers in the conditions of summer planting to improve the quality of seed material. The purpose of the study was to determine the influence of the physiological and biochemical state and varietal characteristics of potato plants on the ability of freshly harvested tubers to form high-quality seed material for second-crop potatoes in the Forest-Steppe of Ukraine. Field, statistical, computational, analytical, and laboratory methods were used to conduct the study. It is identified that harvesting the first crop for planting with freshly picked tubers during the flowering phase and within two weeks after its completion is ineffective for some varieties. Therewith, the first crop averages 18.5 t/ha, and the second – 5.1 t/ha. Some varieties have a low germination rate from freshly picked tubers (from 4 to 76%) or are not formed at all. This is due to the accumulation of germination inhibitors (abscisic acid etc.) in maturing tubers, which causes deep natural dormancy of tubers. It is proposed to consider the activity of germination inhibitors in freshly harvested tubers using allelopathic testing, which allows for determining the optimal time for their collection and planting. This ensures germination rate at the level of 80-87%. Therewith, the first crop of tubers is from 10.1 to 15.0 t/ha, and the second – from 26.2 to 9.3 t/ha. The dependence of the content of abscisic acid with the accumulation of starch in tubers allows visually determining their suitability for germination by the chemical reaction of vegetable juice with an iodine solution. The practical value of the study lies in the possibility of obtaining two crops of seed potatoes per year, while the first crop is formed in 60-70 days, and the second – 90-100 days from planting. Despite the relatively low yield, the resulting seed material is physiologically young, free from diseases and has a high productivity potential. This allows for shortening the seed production scheme, increasing the reproduction rate of potatoes, and saving resources