Molecular Soil Biology 2025, Vol.16, No.6, 306-313 http://bioscipublisher.com/index.php/msb 311 6.3 Changes in yield components under water stress In water shortage conditions, crop yields mainly drop for two reasons: fewer tubers are formed, and the individual tubers become lighter. For example, with insufficient water and frequent irrigation, plants may produce more tubers, but they will weigh less. However, if the water shortage is severe, this effect is less noticeable. A reduction in leaf area and weakened photosynthesis result in less dry matter production (Mora-Sanhueza et al., 2025; Pan et al., 2025; Zhang et al., 2025). In Ukraine, a study comparing different varieties showed no major difference in the number of tubers per plant, which ranged from 7.7 to 8.9. However, the tuber weight varied widely (Yatsenko and Yatsenko, 2025). For mid- and late-maturing varieties, when water stress occurs during starch accumulation, the first noticeable change is a decrease in tuber weight, while the number of tubers stays fairly constant. 7 Discussion 7.1 Yield differences among varieties under low water If there isn't enough water during the tuber formation stage, photosynthesis is closely linked to the final yield, with about a 0.95 correlation. However, during the mature stage, the biomass of the aboveground parts is negatively related to the yield. In conditions with limited water, high-yield, drought-resistant varieties usually have fewer leaves. These plants keep a moderate leaf area, which helps photosynthesis stay stable. This way, more dry matter goes to the tubers instead of the aboveground parts (Zhang et al., 2025). A study in eastern India looked at 21 potato varieties. The mid-maturing high-yield variety "Kufri Arun" and the early-maturing variety "Kufri Pukhraj" both gave high yields, but in different ways. "Kufri Arun" kept a high tuber biomass ratio (TBR) after 60 days of growth, while "Kufri Pukhraj" reached a high TBR in the first 60 days. Mid-maturing varieties are more affected by water shortage later on, while early-maturing varieties are more affected during the early growth stage (Das et al., 2021). 7.2 Meaning for irrigation management in potato farming Studies from Chile and the Hexi Oasis show similar findings. Reducing irrigation by 20%~25% (for example, using 75% T1 or 55%~65% of field capacity) usually does not affect marketable yield when compared to full irrigation. At the same time, water use efficiency can increase by about 18%-22%, and irrigation water productivity can improve by 7%~13% (Li et al., 2025; Mora-Sanhueza et al., 2025; Pan et al., 2025). However, when water deficit becomes stronger, or when it happens during very sensitive stages such as tuber initiation and bulking, yield loss increases fast and can reach 18.9%~40%. In practice, light water deficit can be used first at the seedling stage and part of the vegetative stage. For medium- and late-maturing varieties that are sensitive during tuber formation and bulking, water supply should stay close to full irrigation in these stages. For drought-tolerant or early varieties, moderate water reduction can be used in part of the mid stage. In areas with very limited water, using varieties that stay stable under climate change and water fluctuation can further lower risk. Examples include varieties with high adaptability and stable performance such as ‘Alka’ and ‘Vostorg’. 7.3 Comparison with earlier studies The 75% T1 treatment plan can reduce irrigation water consumption by approximately 25% while maintaining the same output. Mild to moderate underirrigation has little impact on yield. Moderate deficiency irrigation can increase the content of starch, sugar and protein in tubers. Excessive water deficiency or deficiency irrigation at inappropriate times (such as during the tuber formation and expansion period) can lead to decreased yield and quality issues (Zhang et al., 2025). If some varieties show significant yield losses after a 20%~30% reduction in irrigation water usage, it may be because the water deficiency occurs precisely during their main tuber swelling period (Mora-Sanhueza et al., 2025). Acknowledgments We would like to express our gratitude to the two anonymous peer researchers for their constructive suggestions on our manuscript. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.
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