Cytological basis and key metabolite profiling of fresh tobacco leaves with different oiliness indices in Yunyan 87

Introduction Tobacco oiliness index is a key chemical trait that significantly influences tobacco quality. Methods To elucidate the cytological features and key metabolites underlying varying relative oiliness indices, fresh Yunyan 87 tobacco leaves were analyzed by microscopic and metabolomic profiling. Results The results indicated that leaves with high oiliness exhibited a tighter tissue architecture, characterized by closely packed mesophyll cells and reduced intercellular spaces; conversely, leaves with low oiliness showed a looser arrangement. The levels of cembratriene-diols, methyl nonanoate, and methyl palmitate in trichome exudates were markedly elevated in high-oil leaves compared with those in low-oil leaves. High-oil leaves exhibited a significantly greater abundance of starch grains and osmiophilic granules. In contrast, low-oil leaves displayed localized chloroplast swelling and mild mitochondrial vacuolation, suggesting insufficient or imbalanced accumulation of intracellular storage substances. The concurrent elevation of oleic acid, a signature lipid metabolite, exhibited a strong positive correlation with relative oiliness index and holds promise as a reliable biomarker for identifying and selecting high-oil tobacco leaves. Discussion These findings offer a theoretical reference for the targeted breeding and agronomic management of high-oil tobacco varieties.