Molecular Plant Breeding 2025, Vol.16, No.1, 73-81 http://genbreedpublisher.com/index.php/mpb 76 Figure 2 Phenotypic and genetic response of Beauregard and Tanzania sweet potato varieties to the application of polyethylene glycol (PEG) (Adopted from Lau et al., 2018) Image caption: (a) Plantlets incubated in untreated media or 25% PEG media at 24 and 48 hr after stress (HAS). (b) Principal component analysis of individual biological replicates using variance stabilizing transformed read counts. Each point represents a biological replicate (Adopted from Lau et al., 2018) 4.3 Field trials and phenotypic assessments Field trials are essential for validating the drought tolerance of newly developed sweet potato varieties under real-world conditions. These trials involve growing the new varieties in drought-prone areas and monitoring their phenotypic responses, such as yield, tuber quality, and physiological traits. The study by Qin et al. (2019) demonstrated the effectiveness of greenhouse methods to screen potato genotypes for drought tolerance, which can be adapted for sweet potatoes. Additionally, phenotypic assessments, including measurements of gas exchange, chlorophyll content, and specific leaf area, are conducted to correlate these traits with drought tolerance. The integration of high-throughput phenotyping platforms, as mentioned in Obidiegwu et al. (2015), can further enhance the precision and efficiency of these assessments. 5 Key Genes and Pathways Identified for Drought Resistance 5.1 Identification of candidate genes related to water retention The identification of candidate genes related to water retention is crucial for developing drought-resistant sweet potato varieties. One such gene is IbMIPS1, which encodes myo-inositol-1-phosphate synthase. This gene has been shown to enhance drought tolerance by up-regulating genes involved in inositol biosynthesis, phosphatidylinositol (PI), and abscisic acid (ABA) signaling pathways. The overexpression of IbMIPS1 in transgenic sweet potato plants significantly increased the content of inositol, inositol-1,4,5-trisphosphate (IP3), phosphatidic acid (PA), Ca²⁺, ABA, K⁺, proline, and trehalose, which are critical for water retention and stress response (Zhai et al., 2016). 5.2 Role of abscisic acid (ABA) pathways in drought response ABA plays a pivotal role in the drought response of sweet potato by mediating various physiological and molecular processes. The IbPYL8-IbbHLH66-IbbHLH118 complex is a key component in the ABA-dependent drought response. Under drought stress, ABA accumulates and promotes the formation of this complex, which interferes with the repression of ABA-responsive genes by IbbHLH118, thereby activating ABA responses and enhancing drought tolerance. The ItfWRKY70 transcription factor, induced by ABA, enhances drought tolerance
RkJQdWJsaXNoZXIy MjQ4ODYzNA==