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.