The decline in the mean performance from F₁ to F₂ was noted for plant height, kernel weight and yeild in cross 1 and 2 and spikelets/ear in cross 1. In almost all cases the means of F₂ populations appeared to be intermediate between parental means. While judging the crosses for mid-parental values, cross 2 appeared to be superior to cross 1. From basic genetic considerations BAKER (1980) viewed that the use of mid-parent value should be an effective a priori method of selection among crosses even under severe type of epistasis.

Table1. Mean values and heterosis for grain yield and its components in two 6x triticale crosses

Generation mean squares of crosses were partitioned into various genetic effects as shown in Table 2. Mean squares fitting due to additive gene effects were significant for all the traits in each cross, while mean squares fitting due to dominance gene effects were significant for plant height, number of kernels, kernel weight and yield in cross 1 and heading date and kernel weight in cross 2. With exception of yield in cross 1 the maguitude of additive mean squares was larger than that of dominance mean squares. It should be, however, noted that the estimate of dominance gene effects are effected by balancing of plus and minus values (ambidirectional dominance). Significant mean squares due to deviations from additive-dominance model indicated the role of epistasis for plant height, number of spikelets and kernel weight in both crosses and heading date and yield in cross 2. Since the magnitude of deviations mean squares approached significance for other characters, the epistatic gene action for them could not be ignored.

The present study, thus, indicated predominant additive nature of genetic effects in cross 1 . This signifies the early generation selection in cross 1 can be made effective for bringing an improvement in several characters including yield. On other hand, non-additive genetic effects were frequently detected in cross 2, however, their contribution relative to additive effects was minor. Conventional selection in this cross should be delayed to later generations for a more tangible advance.

Literature Cited

BAKER, R.J. 1980. Basic genetic considerations in plant Breeding. Barley News Letter 24 : 40.

HAYMAM, B.I. 1958. The separation of epistatic from additive and dominance variation in generation means. Heredity 12 : 371-390.

KROLOW, K.D. 1977. Problems and prospects of triticale. Plant Research and Development 6 : 134-148.

QUALSET, C.O., E.A. RUPERT & J.D. PRATO 1973. Triticale in California : Review of current research and appraisal as a new crop. Int. Symp. on Triticale, Texas Tech. Univ., Lubbock.

ZILLINSKY, F.J. 1974. CIMMYT Review : 19-26.

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