3.1. The Rate of Spread of Potato Blight
The rate of spread of potato blight refers to the speed at which the fungal pathogen
Phytophthora infestans, which causes late blight disease, spreads within a potato crop (
Figure 1).
Several factors influence the rate of spread of potato blight, including environmental conditions such as temperature, humidity, and rainfall, as well as agronomic practices, host plant resistance, and the presence of the pathogen in the vicinity. Warm, humid conditions are particularly conducive to the rapid spread of the disease, as they promote the growth and dispersal of the pathogen’s spores.
Table 5 presents the coefficients of the rate of late blight spread for the years 2018-2020, dependent by location (Parczew and Uhnin) and cultivation systems (Ecological and Integrated).
In 2018, the rate of late blight spread in Parczew was 0.192 under the Ecological system and 0.200 under the Integrated system. In Uhnin, the rates were 0.140 and 0.132, respectively. In 2019, the rates in Parczew were 0.201 (Ecological) and 0.224 (Integrated), while in Uhnin, they were 0.165 (Ecological) and 0.142 (Integrated). In 2020, the rates in Parczew were 0.138 (Ecological) and 0.132 (Integrated), and in Uhnin, they were 0.114 (Ecological) and 0.120 (Integrated).
These coefficients serve as indicators of the rate at which late blight spreads under different conditions, providing valuable insights for disease management and agricultural practices.
Hydrothermal coefficients (k) indicate the balance between precipitation and temperature during specific months, specifically June, July, and August. The index values categorize the conditions into different moisture levels ranging from extremely dry to extremely humid.
Coefficients of the rate of potato blight spread were higher in Parczew than in Uhnin in all years of the study (
Table 5). This could be attributed to different weather conditions favoring the faster emergence and spread of the pathogen (
Table 4), as well as soil conditions, as the soils in Parczew exhibited significantly higher humus content and higher soil pH (
Table 2 and
Table 3).
Table 5 provides insight into meteorological conditions and their impact on the development of Ph. infestans over a three-year period, which may be valuable for understanding disease dynamics and optimizing crop management strategies. The infection of 50% of the potato leaf blade surface is an indicator of the degree of plant infection by the pathogen known as Ph. infestans, which causes the disease commonly known as potato blight. This is a significant criterion because it indicates the point at which the infection reaches a level that has a significant impact on yield. When the infection covers 50% of the leaf blade surface, it negatively affects the plant’s ability to photosynthesize and produce tubers, ultimately leading to a reduction in yield. Therefore, this moment is crucial for assessing the effectiveness of disease management strategies and making decisions regarding further disease control actions.
Plant production systems and the resistance of potato varieties had a significant impact on the rate of pathogen spread in plants (
Figure 2,
Figure 3,
Figure 4,
Figure 5,
Figure 6,
Figure 7 and
Figure 8). Ph infestans spread the fastest over time. infestans on the medium-early potato variety ‘Irga’, not resistant to late blight, with resistance 2 on a 9-point scale.
In the ecological system, 50% of potato leaf blade infection occurred on average 43 days after the appearance of the first late blight spots, which determine the accumulation of tuber yield, while in the integrated system, this moment occurred 15 days later (
Figure 2).
Potato was infected sooner in the ecological system. The average infection of 50% of the leaf blade surface, determining yield accumulation, occurred 44 days after the first infection symptoms (spots) were observed. In the integrated cultivation system, where protective measures against potato blight were applied, plant infection by
Ph. infestans occurred, on average, 16 days later than in the ecological system. The effectiveness of plant protection against the blight depended on the plant’s resistance to the pathogen and their reaction to fungicide application (
Figure 2).
Leaf blight developed the slowest in the medium-early variety ‘Boryna’ with resistance of 5.5° on a scale of 9°. Infection of 50% of leaf blades of medium early, quite resistant to Ph. infestans of the ‘Boryna’ variety (5.5° on a scale of 9°) occurred 90 days after the first plague spots appeared in the organic system, and 6 days later in the integrated system (
Figure 3).
Figure 4 depicts the rate of potato blight spread on plants of the moderately early, edible variety ‘Irga’ in both ecological and integrated cultivation systems. Critical infection, affecting 50% of leaf blades for this variety, occurred after 36 days from the first observation of late blight spots in the ecological system and 3 days later in the integrated cultivation system.
Figure 5 depicts the rate of potato blight spread on plants of the moderately early, edible variety ‘Jurek’ in both ecological and integrated cultivation systems. Critical infection, affecting 50% of leaf blades for this variety, occurred after 41 days from the first observation of late blight spots in the ecological system and 7 days later in the integrated cultivation system.
Figure 6 illustrates the impact of resistance characteristics of the moderately early, edible variety ‘Mila’ and cultivation systems on the timing of infection of 50% of potato leaf blade surface. For this variety with a resistance rating of 5 on a 9-degree scale, critical leaf blade surface infection occurred as early as 34 days after the first observation of late blight spots in the ecological system, and due to full protection against potato blight in the integrated system, it occurred 21 days later (
Figure 6).
The effect of resistance characteristics of the moderately late, starch variety ‘Amarant’ and potato cultivation systems is presented in
Figure 7. Critical infection, affecting 50% of the leaf blade surface of this variety, occurred after 54 days from the appearance of the first late blight spots in the ecological system. However, the integrated system, utilizing organic and mineral fertilization along with full protection against potato blight, contributed to extending this period by 45 days (
Figure 7).
The response of the moderately late, edible variety ‘Jelly’ to the applied cultivation systems is presented in
Figure 8.
In the ecological cultivation system, infection of 50% of the leaf blade surface of the ‘Jelly’ variety was observed after just 34 days from the appearance of the first late blight spots, while the integrated cultivation system extended this period by 30 days (
Figure 8).
Table 6 presents the results regarding the regression coefficient of the spread rate of
Ph. infestans for the examined potato varieties and two production systems. For each variety, resistance to late blight is provided on a 9-degree scale, where a higher number indicates greater resistance to late blight. The regression coefficients determine how quickly the pathogen spreads for each variety and production system. Lower coefficient values suggest slower pathogen spread, indicating greater resistance of the variety or more effective disease control strategies in the specific production system. Variability in the regression coefficient values across varieties and production systems suggests that the effectiveness of variety resistance or disease prevention strategies may depend on specific growing conditions.
Resistance Levels: Varieties with higher resistance levels, such as ‘Amarant’ (6.5) and ‘Boryna’ (5.5), generally exhibit lower infection coefficients compared to those with lower resistance levels, like ‘Irga’ (2.0). Crop Production Systems: Across all varieties, the ecological crop production system tends to result in slightly lower infection coefficients compared to the integrated crop production system. Varietal Performance: ‘Jelly’ and ‘Mila’, both with a resistance level of 5.0, show relatively high infection coefficients compared to varieties with similar resistance levels. This suggests that factors beyond resistance level, such as environmental conditions or cultivation practices, may influence varietal performance in terms of late blight resistance (
Table 6).
Overall, the table underscores the importance of both varietal resistance and crop production practices in managing late blight infection. Additionally, it highlights the need for further investigation into factors influencing varietal performance under different production systems to optimize disease management strategies.
Overall, these results underscore the importance of both variety resistance and the implementation of effective crop management strategies, including plant protection, fertilization, and pest control, in minimizing the risk of potato blight occurrence and spread, as well as ensuring high yield productivity. This indicates that the integrated production system contributed to delaying the onset of infection on the leaf blade surface for all varieties compared to other cultivation methods. The longer delay observed for certain varieties, such as ‘Jelly’ and ‘Amarant’, suggests that these varieties may possess inherent traits or characteristics that make them more resilient to infection under integrated production conditions. Conversely, varieties with shorter delays, like ‘Irga’ and ‘Jurek’, may require additional management practices or interventions to mitigate the risk of early infection. These findings emphasize the importance of considering both the cultivation system and varietal characteristics when implementing strategies to manage potato late blight effectively.
3.2. Total and Commercial Yield of Tubers
Total and marketable yields of potatoes differed significantly depending on the potato varieties and production systems (
Table 7). In the ecological system, the total yield of tubers was lower by 49.1% and the marketable yield by 52.3% compared to the integrated system. Moreover, it was calculated that extending the potato vegetation period by 1 day in the integrated cultivation system, due to the combined application of fertilization and plant protection measures, contributed to an increase in tuber yield by 795.9 kg per hectare (
Table 7).
Medium-early variety ‘Jurek’ had the lowest yields. The ‘Amarant’ variety followed closely behind ‘Jurek’. In terms of total yield, the ‘Irga’ and ‘Jurek’ varieties were homogeneous, whereas for marketable yield, the ‘Jurek’ and ‘Mila’ varieties were homogeneous in this trait (
Table 7).
The integrated cultivation system generally resulted in higher total and marketable yields compared to the ecological system for most varieties, indicating the effectiveness of the integrated approach in increasing potato productivity. In this system, the ‘Boryna’ variety exhibited the highest yield, while the ‘Jurek’ and ‘Irga’ varieties had the lowest total yields, and the ‘Irga’ and ‘Mila’ varieties had the lowest marketable yields. Additionally, the ‘Amarant’ and ‘Jelly’ varieties were homogeneous in terms of these traits (
Table 7).
In the ecological system, the ‘Boryna’ variety also produced the highest total yield, while the ‘Jurek’ variety had the lowest yield. The ‘Irga,’ ‘Jelly,’ and ‘Mila’ varieties were homogeneous in terms of this trait. For marketable yield, the response of the varieties to the cultivation systems was also varied. The ‘Boryna’ variety responded best to the ecological system, followed by the ‘Amarant’ variety, while the remaining varieties were in the same homogeneous group (
Table 7). Significant differences in yields between varieties and between the ecological and integrated systems highlight the importance of variety selection and production system management in optimizing potato yields.
Table 8 presents the impact of the experiment locations (Parczew and Uhnin) and potato varieties on total and marketable yields from 2018 to 2020. In both Parczew and Uhnin, the ‘Boryna’ variety achieved the highest total and marketable yields, followed by the ‘Amarant’ and ‘Jelly’ varieties. The variety with the lowest marketable yield was ‘Jurek,’ with homogeneous traits observed in several varieties.
Generally, most varieties yielded higher in Uhnin compared to Parczew, suggesting potential differences in soil and climate conditions between the two locations. Significant differences in yields between varieties and locations were also observed, as indicated by LSD values. For total yield, the ‘Boryna’ variety achieved the highest yield regardless of location, while the ‘Jurek’ variety had the lowest yield in Parczew, and the ‘Irga’ variety had the lowest yield in Uhnin. A similar varietal response to location conditions was observed for marketable yield. The interaction effect between location and variety underscores that the impact of a variety on yield can vary significantly depending on the location (
Table 8).
The analysis of total and marketable tuber yields of the studied potato varieties, depending on the years of research and varieties, showed significant differences in productivity both between years and between varieties (
Table 9). The highest yields, both total and marketable, were obtained in 2020, which had favorable weather conditions for potatoes, while the lowest total and marketable tuber yields were obtained in 2019, which experienced a shortage of rainfall and unfavorable distribution during the potato growing season. The ‘Boryna’ variety consistently showed the highest total and marketable yields across all three years, with an average total yield of 47.0 t ha
-1 and an average marketable yield of 45.7 t ha
-1. Conversely, the medium-early variety ‘Irga’ had the lowest yields compared to other varieties, with an average total yield of 25.0 t ha
-1 and an average marketable yield of 22.8 t ha
-1. Varieties with LSD values at p<0.05 that did not differ significantly from each other are considered to produce homogeneous yields. For total yield, the ‘Boryna’ and ‘Amarant’ varieties produced homogeneous yields in 2018 and 2019, indicating no significant differences between these varieties. Homogeneous total tuber yields were also observed for the ‘Irga,’ ‘Jelly,’ ‘Jurek,’ and ‘Mila’ varieties in the dry year of 2018, and for the ‘Irga,’ ‘Jurek,’ and ‘Mila’ varieties in 2019 (
Table 9).
For marketable yield, the ‘Boryna’ and ‘Amarant’ varieties also showed homogeneous yields in 2018 and 2019. Additionally, the ‘Irga’ and ‘Jurek’ varieties achieved homogeneous marketable yields in 2018 and 2020 (
Table 9).
Additionally, an interaction between years and varieties was observed for both total and marketable yields. This interaction is evident in the yield fluctuations. Some varieties consistently produced stable yields throughout the years of the study, while others showed variability in this trait. For example, while the ‘Boryna’ variety consistently maintained a high yield level, the ‘Irga’ and ‘Jelly’ varieties exhibited different yield levels over the years 2018-2020.