# Classification of Potato Varieties Drought Stress Tolerance Using Supervised Learning
## 4 Discussion  
To maintain sustainable potato production, we must adapt our cultivation practices and develop stress-tolerant potato cultivars that are appropriately engineered for the changing environment. Yet, the lack of data on the underlying mechanisms of potato plant resistance to abiotic and biotic stress and the ability to predict future outcomes constitutes a major knowledge gap. It is a challenge for plant scientists to pinpoint the means of improving tuber yields under increasing CO\({}_{2}\), high temperatures, and drought stress including the changing patterns of pest and pathogen infestations [36]. Understanding stress-related physiological, biochemical, and molecular processes is crucial to developing screening procedures for selecting crop cultivars that can better adapted to changing growth conditions. As has been emphasized many times, the potato is a species sensitive to soil drought. For many years, simple indicators have been searched to determine the tolerance of individual genotypes to drought stress [14; 37; 38]. Unfortunately, no such unambiguous measures have been found so far. The plant's response to drought stress is multifaceted and has many elements. In our work, we attempted to assess the tolerance of as many as 50 potato genotypes tested over 15 years to drought stress based on their response to the environmental conditions described by the climatic water balance, and we assessed the relationship between the yield decline under drought stress and some morphological features of plants. Using these relationships, an attempt was made to create a mathematical model describing these relationships. Based on the investigated data, it is quite difficult to predict the yield decrease of individual varieties based only on the Climatic Water Balance, even taking into account their drought stress tolerance group. It would seem that the cultivars with the highest tolerance should be characterized by the lowest yield decrease regardless of the applied stress level, which was not confirmed in all cases. It should be noted, however, that, in different years, the set of varieties was different, which, to some extent, could have influenced the interpretation of the results and the development of the model. As already mentioned, many researchers are looking for simple indicators characterizing a cultivar's tolerance to drought and, consequently, to the yield. As far as the morphological features of the plant are concerned, for sure is the mass and size of the leaves, which shape the size of the plant's assimilation area and the tuber yield. Our research also confirmed these dependencies. The greatest positive correlation regarding the morphological features, resistance to drought, and yield size were obtained for the mass  
Figure 4: Local explanation summary with SHAP values for the final model (config 5) output. of leaves and the assimilation area, similar to Reference [39]. A positive correlation also took place in the case of the mass of stems. Although, in our research, these correlations were not as high as could be expected. Interestingly, the highest significance concerned the cultivars from the group with medium and low resistance to the tested stress. The relationships between the leaf assimilation area of potato cultivars and drought tolerance are less well-understood [40]. Most research on potato canopy traits is more concerned with the effects of drought on the canopy rather than the effects of canopy traits on drought tolerance [26]. This is understandable, as drought stress affects all plants by limiting the stable photosynthetic productivity at the chloroplast, leaf, and canopy levels [41]. However, potato canopies have an important role in regulating evapotranspiration [42], dry matter partitioning [43], and tuber yields [40] under drought conditions. The linear modeling with one feature only seems to provide too weak predictors of the potato cultivars' drought stress tolerance.