Dual Drought–Lead Stress Tolerance in Solanaceae: Morphophysiological and Genetic Integration

Drought and lead (Pb) pollution are two major abiotic stress factors that often occur together in low-input and peri-urban farmlands. While both have been studied individually in crops such as tomato, pepper, and eggplant (Solanaceae), few studies have examined their combined effects. This is notable, as many farmers face both challenges simultaneously. Much of the existing literature focuses on either drought or heavy metals such as cadmium or arsenic, often overlooking Pb and drought as a dual stress. This review addresses that gap by examining how Solanaceae crops respond to both stresses at physiological, anatomical, and genetic levels. Based on a structured review of 83 peer-reviewed studies published between 2000 and 2024 and retrieved from Google Scholar, PubMed, Scopus, and Web of Science, the synthesis highlights key traits such as stomatal regulation, root system architecture, antioxidant enzyme responses, and detoxification pathways. Antioxidant activity and HMA3-mediated Pb sequestration emerged as convergent mechanisms supporting dual-stress resilience across Solanaceae species. The review draws on recent findings, including CRISPR-based gene editing in tomato, to highlight genes linked to stress tolerance. It also compares cultivated varieties and landraces to identify genotypes with improved adaptability. Gaps in the literature are emphasized, particularly the absence of dual-stress field trials, underutilization of wild relatives, and lack of genotype × environment × stress (G×E×S) data to guide breeding. A conceptual model is proposed to integrate these dimensions into future strategies aimed at developing Solanaceae crops that perform reliably under combined drought and Pb exposure.