EFFECT OF GENOTYPE AND LEAF POSITION ON PIGMENTS AND THEIR DEGRADATION DERIVATIVES IN BURLEY TOBACCO

Abstract

Leaf pigments and their derivatives play an important role in the colour and aroma of tobacco. Chemical and biochemical quality constituents of tobacco (Nicotiana tabacum L.) are influenced by leaf position on stalk, cultural practices, genotypes and curing methods. Leaf curing is an important and essential post-harvest process in tobacco production which is likely to have a bearing on leaf quality, particularly in terms of pigments. The present study, therefore, assessed the effects of genotype and leaf position on pigments and their derivatives in air cured burley tobacco. The pigments identified in cured burley tobacco leaf included chlorophylls, carotenoids, pheophytin, chlorophyllide, protoporphyrin and magnesium protoporphyrin. Total chlorophyll (Tchl) content varied from 50.9 to 130 μg/g among the leaf positions and varieties. Tchl content was significantly higher in the variety Banket A1 compared to YB4 and middle position leaves (3rd pick) showed significantly higher levels of Tchl compared to the lower and top position leaves. Carotenoid content varied from 131 to 199 μg/g among the leaf positions and genotypes. The variety YB4 showed higher levels of carotenoids but lower levels of more polar carotenoids (MPC) and less polar carotenoids (LPC) than variety Banket A1. The carotenoid content increased with increase in leaf position with exception at 2nd pick and top position leaves showed maximum carotenoids. The variety Banket A1 showed significantly higher levels of Pheophytin a (Phe a) compared to YB4. Pheophytin b content was 2.3 times higher in the variety Banket A1 compared to YB4. Variety Banket A1 showed higher levels of MgPP and protoporphyrin compared to variety YB4. Chlide a content between the two varieties ranged from 0.06 to 1.73 mg/g whereas chlide b content varied from 1.06 to 2.80 between the varieties and among the picks. The variety YB4 showed significantly higher content of Chlide b compared to Banket A1. Pheophorbide compounds were not detected in both the varieties. The end product of the chlorophyll degradation may be chlide in tobacco and the degradation of chlorophyll pigments after curing was greater in YB4 compared to variety Banket A1. Thus, the advanced breeding line YB4 showed lower levels of chlorophyll pigments indicating the higher breakdown which may be leading to the formation of higher levels of aroma compounds.