PHYSIOLOGICAL BASIS OF HETEROSIS IN BIDI TOBACCO (nicotiana tabacum L.)
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Date
1998-08
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AAU, Anand
Abstract
The present investigation on Physiological basis of heterosis was carried out by comparing two hybrids viz. ms GT 5 X 259-51-31 (SH) and GT 5 x 259-51-31 (FH) with their parents in Randomized Block Design with six replications at the Bidi Tobacco Research Station, Gujarat Agricultural University, Anand during 1995-96 and 1996-97 crop season. The positive heterotic effects exhibited by both the hybrids for growth and developmental characters viz., plant height, number of leaves/plant, leaf length and breadth, leaf area as well as dry weight/unit area, indicated that hybrids were superior to their respective parents but for days to topping/flowering they were inferior to their better parent. The hybrids had very low but positive heterotic effect in relative growth rate (RGR) and leaf area ratio (LAR). However, maximum heterotic effect was noticed in leaf area duration (LAD) and leaf area index (LAI) during all the stages of growth. Incase of net assimilation rate (NAR) low and negative heterotic effect was observed. The high and positive heterotic effect in chlorophyll contents^ (a, b and total) indicated more photosynthetic activity in the leaf of hybrids as compared to their parents during entire growth period. The data on chemical constitutents of leaf viz., nicotine and reducing sugar per cent indicated small but positive heterotic effect in both the hybrids, which is good from the quality point of view. The results of nutrient contents (NPK) in leaf indicated that hybrid cointained higher nutrients than parents, which showed more nutrient requirement and uptake by the hybrids, which inturn has reflected in vigour as assessed by growth parameters and final dry weight of leaf. Correlation coefficient studies indicated that leaf length and breadth and thereby leaf area, LAI, LAD as well as dry weight/unit leaf area were significantly correlated with yield at most of the growth stages, while RGR, LAR and NAR were correlated only at certain stages of the crop growth. In general, the sterile source of cytoplasm (SH) was equally good and remained at par with fertile source (FH) in mean performance indicating that both were similar in respect to most of the characters studied. As both the hybrids were equally good and gave significantly higher yield (about 19 %) than parents without impairing the leaf quality of the produce, the cms lines could safely and profitably be used in heterosis breeding programme in bidi tobacco crop. The present investigation led us to believe that the heterosis is a complex phenomenon governed by morphophysiological characters and bio-chemical reactions. Based on the above findings it is suggested that more emphasis should be given to leaf area, dry weight/unit leaf area and chlorophyll contents of the leaf in bidi tobacco hybridization programme as leaf is the main economical part of the crop.
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