Chlorophyll a and b and carotenoid content in the leaves of sesame (Sesamum indicum L.) collection genotypes under the conditions of Tashkent Region, Republic of Uzbekistan

Background. Under the conditions of climate aridization and increasing water deficit in Uzbekistan, sesame (Sesamum indicum L.) is considered a promising oilseed crop, capable of adapting to high temperatures and limited water availability. However, physiological and biochemical features of the photosynthetic apparatus in different sesame genotypes remain insufficiently studied, which limits targeted breeding of stress-tolerant forms.

Materials and methods. Twelve sesame collection genotypes of diverse ecogeographic origin, grown in Qibray District, Tashkent Region, in 2025, were studied. The content of chlorophyll a, chlorophyll b, their total, and carotenoids in leaves was measured spectrophotometrically after extraction with 96% ethanol at the stages of budding, flowering, and the onset of capsule formation, using Lichtenthaler’s formulas.

Results. The concentration of chlorophyll a (Chl a) was found to remain relatively stable during the generative period (1.06–1.18 mg/g), whereas the content of Chl b exhibited pronounced phase-dependent dynamics, decreasing toward flowering and increasing in the stage of capsule formation. The highest values of total chlorophyll (1.97 mg/g) were recorded in the late development stage. The Chl a/b ratio varied from 1.6 to 2.4, reaching its maximum during flowering, and minimum during fruit formation. The Car/Chl (a+b) index increased to 0.195 during flowering and declined to 0.108 at the onset of fruit development. Among the genotypes, K66, K161, and K1396 showed the highest levels of chlorophylls and carotenoids, which attest to their enhanced photoprotective capacity and potential stress tolerance.

Conclusion. The obtained data confirm pronounced phase-related and genotypic variability of the pigment system in sesame leaves. Genotypes K66, K161, and K1396 may be recommended as source material for breeding programs aimed at improving drought tolerance and productivity of the crop under arid conditions.

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