Molecular Plant Breeding 2024, Vol.15, No.6, 379-390 http://genbreedpublisher.com/index.php/mpb 386 Figure 3 World map of the 1 973 sweet potato cultivars and breeding lines tested in the intentional exposure and control trial for HS tolerance (Adopted from Heider et al., 2020) Image caption: a, Originlocation of each cultivar and breeding line overlaid with the Worldclim maximum temperature of the warmest month. Blue dots indicate heat-tolerantcultivars under future climate scenario RCP 8.5 (tolerance to heat stress >1). The experimental field site for sweet potato heatscreening is marked with a red star. b, Visual drone-based mapping of the 4 040 test plots at the experimental field site in Piura, Peru. c, Close-ups on thedemarcation of sweet potato cultivar plots in the visual map. d, Corresponding high-precision thermographic image of plant canopy temperatures under HS conditions. Temperatures represent means of the warmest month in a and snapshot of surface canopy temperatures in b and d (Adopted from Heider et al., 2020) 7.2 Agronomic practices to enhance adaptation Agronomic practices play a vital role in enhancing the adaptation of sweet potato varieties to different environmental conditions. Multi-trait selection indexes, such as those used in the CropInd tool, help breeders identify genotypes with superior agronomic performance across multiple environments (Rosero et al., 2023). These practices include selecting for traits like total and commercial fresh root yield, survival percentage, and stability. Additionally, understanding the physiological and biochemical features of drought-tolerant varieties can inform crop management strategies for drought mitigation (Sapakhova et al., 2023). By employing these practices, breeders can develop varieties that are better suited to withstand environmental stresses. 7.3 Long-term sustainability and climate resilience For long-term sustainability and climate resilience, it is crucial to exploit the intraspecific diversity of sweet potato. This diversity serves as a reservoir for traits that confer tolerance to abiotic stresses, such as extreme heat and drought (Dwivedi et al., 2017; Heider et al., 2020). The identification of heat-tolerant cultivars and breeding lines, along with traits predictive of heat tolerance, underscores the importance of maintaining genetic diversity for future crop resilience (Heider et al., 2020). Moreover, integrating traditional and molecular breeding methods, along with biotechnological approaches, can enhance the drought tolerance and overall resilience of sweet potato varieties (Sapakhova et al., 2023). These strategies ensure that sweet potato remains a viable crop in the face of climate change, contributing to food security and sustainable agriculture. 8 Challenges in Exploiting Genetic Diversity for Crop Improvement 8.1 Limited genetic resources and bottlenecks One of the primary challenges in exploiting genetic diversity for crop improvement is the limited availability of genetic resources. Genetic bottlenecks, often resulting from domestication and selective breeding, have reduced the genetic variability within cultivated species. For instance, the genetic diversity of sweet potato accessions shows significant variability, but the number of cultivars available on the market remains low, limiting the potential for genetic gains (Vargas et al., 2020). Similarly, the genetic diversity of potato has been maintained over centuries, but the introduction of new genetic groups is still necessary to enhance the crop's resilience and productivity (Pandey et al., 2021; Spanoghe et al., 2022).
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