## 2 Results and Discussion
The inoculation of phytopathogens (_Fusarium oxysporum_, _Pectobacterium carootovorum_, and _Rhizzoctonia solian_) to seed potatoes on 10 February had a varied effect on plant development, depending on the time elapsed from pathogen inoculation to plant emergence and also on sprouting stage during the planting of mother tubers into the soil. During planting in plant microcosms, the seed potatoes and the sprouts showed neither mechanical damage nor visible symptoms of disease infestation. Stems, obtained from the seed potatoes inoculated with phytopathogens, developed slightly slower than in control variants without  
Figure 4: Growth kinetics of Impresja potato stems obtained from seed potatoes stored at 4 °C from harvest until 10 February of the following year and then at 15 °C and 80% RH until planting in the soil on 10 March, 10 April, and 10 May. LSD was calculated at the significance level of \(p=0.05\). Figure 3: Percentage of the Impresja sprouted seed potatoes at 20 °C after storage at 4 °C from harvest until inoculation with phytopathogens on 10 February and then at 15 °C and 80% RH before planting in the soil on 10 March, 10 April, and 10 May. C—Control, Fo—_F. oxysporum_, Pc—_P. corotovorum_, Rs—R. _solani_. Means marked with the same letters do not differ statistically at the significance level \(p=0.05\). LSD was calculated at the significance level of \(p=0.05\). adverse influence on flowering. These relationships occurred during cultivation in the three cycles applied; although, all stems and roots obtained from seed potatoes sprouted and planted in May developed the fastest in contrast to the ones planted in April and March (Figure 5). The inoculation of seed potatoes with phytopathogens on 10 February had a more spectacular and negative effect on the kinetics of root growth, assessed on the basis of particular root lengthening and the overgrowth (filling) of the soil profile with the entire root system. In the control variant, non-sprouted seed potatoes planted on 10 March developed roots at the latest. Planting seed potatoes at later dates, when they had sprouts of about 2 (10.04) and 5 cm (10.05), resulted in a gradual acceleration of the root system development. As a result, it took 18, 16, and 14 days for the roots to grow up to a final length of 30 cm when the seed potatoes were planted in March, April, and May, respectively. Compared to the control variant, the infestation of seed potatoes with phytopathogens delayed the beginning of root growth, slowed down the kinetics of their development, and lengthened their growing period to a length of 30 cm. This delay was the lowest for the first planting date (10 March), when the period from phytopathogen inoculation to seed potato planting was the shortest and the buds showed no growth. In the case of subsequent cultivation dates, the negative impact of inoculated phytopathogens on the particular root  
Figure 5: Growth kinetics and final length of Impresja stems obtained from the seed potatoes stored at 4 °C from harvest until inoculation with phytopathogens on 10 February and then at 15 °C and 80% RH before planting in the soil on 10 March, 10 April, and 10 May. C—Control, Fo—F. _oxysporum,_ Pc—_P. corotovorum,_ Rs—_R. solami._ Means marked with the same letters do not differ statistically at the significance level \(p=0.05\). LSD was calculated at the significance level of \(p=0.05\). growth and development of the whole root system was gradually increased. As a result, the dynamic of root growth under the influence of tested phytopathogens inoculation was the lowest after planting seed potatoes on 10 May, compared to the control. The longer time from inoculation up to seed potatoes planting also exhibited greater differences in the degree of the negative impact of _Fusarium oxysporum_, _Rhizctonia solani_, and _Pectobacterium corotovorum_ on the root system development, with _Fusarium oxysporum_ being the most pathogenic species (Figures 6 and 7).