Division of Genetics, Indian Agricultural Research Institute, New Delhi, 110 012, India
1Present address: 10, Aboli Apartments, Opp. Law College, Pune-4.
*Part of the thesis submitted by M G, Bhat for the award of the Ph. D. degree of the Post-Graduate School, Indian Agricultural Research Institute.. New Delhi-110 012.
Inheritance of hairiness and other characters associated with jassid resistance in American cotton were undertaken using six generations of two crosses between jassid resistant and susceptible parents.
For nymphs per leaf, in the cross ‘HH-1 x PS-1’, additive (d) gene effects and additive x dominance (j) type of epistatic gene interaction were significant while additive (d) and dominance (h) gene effects were significant in the cross ‘HH-2 x PS-1’. For jassid susceptibility in the cross ‘HH-1 x PS-1’, only (j) type of ep'static effects were significant while in the cross ‘HH-2 x PS-1’, all gene effects execp(j) were significant. Duplicate type of epistatic gene interaction was indicated in this cross. For hair density, in the cross'HH-1 x PS-1’, (j) epistatic effects played an important role. While in ‘HH-2 x PS-1’ (d) and (j) type of gene interactions were significant. Additive gene effect was much higher than the dominance gene effect in ‘HH-2 x PS-1’. The possibility of obtaining segregates with desirable combinations of less hairiness and higher resistance to jassid was better in the cross ‘HH-1 x PS-1’, probably due to the fact that ‘HH-1’ parent is less hairy as compared to ‘HH-2’ parent. ‘HH-1 x PS-1’ cross appeared to be more promising for fixing hair length character since (i) type of gene interaction, which was operating in this cross, is a fixable type.
