An important problem currently faced by karst rocky desertification management is the degradation of vegetation fruits, which encourages the search for a solution for the sustainable growth of vegetation. Water and fertilizer are key factors affecting crop quality (the formation of soluble solids, protein, amino acids, soluble sugar content, etc.). A comprehensive review of research related to water–fertilizer coupling and crop quality improvement may be beneficial for rocky desertification control. This study analyzed 427 related papers, and the results showed that: (1) the number of published papers showed an “S” curve growth trend over time, indicating that research in the field of water–fertilizer coupling has entered a mature stage after rapid growth, yet it is still in the initial stage in karst areas; (2) the research was mainly theoretical, but also included technology research and development, model construction, demonstration and extension, and monitoring and evaluation; (3) except for research related to greenhouse facilities, the research areas are mainly located in arid and semi-arid regions. The study further revealed (4) the frontier theory of water–fertilizer coupling and crop quality research. Finally, it was found that the theoretical and technical studies related to water–fertilizer coupling and crop quality improvement in karst areas are insufficient. Whether the existing theories and techniques are applicable to karst areas needs further verification. In addition to the areas of selecting germplasm with high water/fertilizer utilization efficiency and tolerance to rocky desertification, further improvement in the dynamic model of water–fertilizer coupling and the construction of a more applicable water–fertilizer coupling model could also be future research hotspots.

Background/Objectives: Peanut landraces (Arachis hypogaea L.) from Guizhou, a karst region of southwestern China, represent an underexploited breeding resource whose phenotypic architecture and marker associations remain insufficiently characterized. Methods: We evaluated 300 local accessions for 30 morphological, agronomic, and quality traits using three-year mean values and analyzed the data using phenotypic diversity statistics, Pearson correlation, stepwise regression, principal component analysis (PCA), hierarchical clustering, and genome-wide association study (GWAS). Results: The collection exhibited substantial phenotypic variation, with Shannon-Wiener indices ranging from 0.54 for leaf color to 2.09 for the equivalent yield per hectare (fresh weight). The Shannon-Wiener index for seedling uniformity was 0.69 in both Liupanshui and Tongren, indicating comparable phenotypic diversity for this trait rather than a direct measure of seedling uniformity. Guiyang accessions had the highest Shannon-Wiener index for sucrose content (1.99). Among 465 trait pairs, 113 showed significant positive correlations and 76 showed significant negative correlations. Stepwise regression retained 100-kernel weight, leaf color, leaf shape, 100-pod weight, main stem height, length of the first branches, and pod number per plant as the main statistical predictors of quality traits. PCA retained eight principal components with eigenvalues above one, which together explained 75.77% of the total variance. A total of 137 accessions had composite scores ≥ 0, and the top ten, including G23212 and G23172, were selected as candidate elite materials. Cluster analysis divided the accessions into four groups and identified 23 representative types. At a suggestive threshold of −log10(P) > 3, the GWAS detected 33 protein- and 27 sucrose-associated SNPs; these loci should be regarded as candidate associations pending validation. Conclusions: Collectively, these results indicate that Guizhou peanut landraces harbor substantial, geographically differentiated phenotypic variation and provide candidate materials and loci for further germplasm evaluation and marker validation.