Patel, A. D.Patel, Prafull A.2018-03-162018-03-161998http://krishikosh.egranth.ac.in/handle/1/5810041879Tobacco is an important cash crop of India. Gujarat state occupying second position in tobacco hectarage and first position in total production and productivity. Considerable important work has been done in this crop but very little information is available on genetics of yield, yield attributes and quality parameters of this crop. With a view to study the magnitude of heterosis and combining ability of four male-sterile lines and eleven elite strains through linextester mating design, a study was taken up at Bidi Tobacco Research Station, Anand during the year 1996- 97. The magnitude of relative heterosis, heterobeltiosis and standard heterosis varied from cross to cross for all the characters under study. Hybrid, GT-4(P3) x 161- 67-36 (Pn) exhibited high heterotic effect for cured leaf yield and its important yield components. The results revealed that GT-5 (P4) among the female parents for cured leaf yield, number of leaves per plant height, leaf length and days to maturity and GT- 7 (Pn) among male parents for cured leaf yield, number of leaves per plant, leaf length and spangle score were better general combiners. Hybrids, GT-5 (P4) x 3-5 8-3 8 (P12) for cured leaf yield, leaf breadth, leaf thickness and spangle score, and GT-4 (P3)xl61-67-36 (P13) for cured leaf yield along with number of leaves per plant and plant height were better specific combinations. Hybrids Anand-2 (P,) x ABD-36 (P9 The estimates of gene effect indicated the involvement of additive gene action in expression of number of leaves per plant, days to maturity and nicotine content. Hence, these traits could be improved through hybridization followed by pedigree method of selection. Involvement of additive as well as non additive or non additive type of gene action in expression of cured leaf yield, days to flower, plant height, spangle score, leaf breadth and leaf thickness were noticed. Hence, for further improvement of tobacco, it would be desirable to develop a gene pool utilizing hybrid vigour or following cyclic method of breeding.enAGRICULTURE, PLANT BREEDING AND GENETICSSTUDYThesis