Field Crop 2025, Vol.8, No.2, 82-92 http://cropscipublisher.com/index.php/fc 85 metabolism. Although the process was quite troublesome, at least now we know which markers to focus on for screening. However, to be fair, even if we know these genetic rules, it still takes a lot of effort to truly cultivate a perfect variety. 3.3 Genetic diversity of stress-resistance traits When it comes to the stress resistance of potatoes, wild varieties are truly a treasure trove. During the years of conducting disease-resistant breeding, it was found that the resistance genes of cultivated varieties were extremely monotonous. On the contrary, those unremarkable wild potatoes (Li et al., 2018b) contained quite a few good things. For devastating diseases like late blight, many of the resistance markers we use now have been dug out from wild species (Afshari et al., 2017). However, wild materials also have their drawbacks. They often bring along some undesirable traits and have to be repeatedly returned for screening. The issue of drought has drawn increasing attention in the past two years. By comparing the performance of leaves when they are short of water, some interesting SNP markers were identified (Zhao, 2024). The most troublesome thing is the prevention and control of nematodes. These substances cause damage underground, and by the time they are discovered, it is often too late. Fortunately, with the advancement of genetic testing technology nowadays, the strength of the plant's resistance can be predicted without waiting for the plant to fall ill. Of course, for these discoveries to be truly applied in the fields, they still need to be verified over a long period of time-after all, the laboratory is the laboratory and the field is the field. 4 QTL Mapping Results 4.1 Identification and contribution analysis of QTLs related to yield traits This QTL localization is quite interesting. The newly discovered site on chromosome III is particularly eye-catching-its impact on yield variation is much greater than expected. However, a more typical case is the situation on chromosomes I and IV (Figure 1), where each locus contributes a portion of the effect, with the least being just over 5% and the most reaching around 16%. This indicates that the yield of potatoes is not determined by just one or two genes; rather, it's more like a group of genes working in coordination. Interestingly, some of these sites control the number of tubers, while others control the weight of individual tubers. Only when combined do they determine the final yield. The laboratory data looks quite clear, but there are always some unexpected incidents in the fields-perhaps there are still some minor sites that we haven't detected. This also explains why high-yield breeding is so difficult, as so many genetic factors have to be gathered together. 4.2 Distribution and effect evaluation of key QTLs for quality traits This analysis of QTL related to potato quality revealed that the key loci for starch content were mainly concentrated on chromosomes I, II and VIII. Interestingly, these loci are all stable in different planting environments (Hara-Skrzypiec et al., 2018), which is good news for breeding. The situation regarding dry matter content and specific gravity is rather complicated-although these two traits seem related, their QTL positions do not overlap at all, indicating that there are two different genetic mechanisms controlling them behind the scenes. The most surprising thing is the genetic pattern of the shape of the tubers. The loci on chromosomes III and X have a particularly significant impact on the appearance of the tubers. However, field observations have found that even if the genotypes are the same, the shape of the tubers is still affected by soil conditions, which indicates that phenotypic prediction cannot rely solely on genotypes. Overall, the genetic regulation of quality traits is more refined than imagined, and each indicator needs to be optimized separately. 4.3 Identification of major QTLs for stress-resistance traits and environment interaction analysis Several findings in this QTL mapping of stress resistance traits are particularly notable. The precocious QTL on chromosome 5 is a "big guy"-it alone can explain 33.55% of the phenotypic variation (Manrique-Carpintero et al., 2018), which is rare among complex traits. However, the resistance to scab disease is relatively scattered. The contribution of loci on chromosomes I and IV is not significant, and it may be necessary for more potent loci to act together. The most troublesome issue is the interaction between genes and the environment: the same early-maturing genotype stands out in cool regions but becomes unremarkable in warm ones. Traits such as plant height and flowering period are even more dependent on the weather. Sometimes, the influence of the
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