| Days to heading is under polygenic control with additive gene action (PARODA
et al., 1972). In the present study, monosomic populations 7A, 3D
and 7D were early indicating the presence of genes for earliness on these
chromosomes of UP 301. The presence of a gene for lateness on 5A was expressed
by delayed heading of 5A monosomic population. Chromosome 7D carrying a
factor for earliness has been reported by DRISCOLL and JENSEN (1964). As
UP 301 is derived from a cross involving Sonora-64, the identification a
gene for earliness on chromosome 3D of UP 301 supports the view of PlRASTEH
and WELSH (1975) who suspected chromosome 3D of Sonora-64 to carry a gene
for earliness. The association of a gene for earliness with chromosome 7A
of UP 301 also agrees with the findings of BOZZINI and GIORGI (1971). The
gene for late heading identified in the present study is also reported by
DRISCOLL and JENSEN (1964) and by LAW et al. (1976). Spike length is predominantly controlled by polygenes with additive gene action (JOHNSON et al., 1966 and KOSNEV and BARES, 1975). The disomic F2 population exhibited longer spike length than either of the parents. This may be because of the complex interaction of the genes controlling this character. Monosomic populations 2B and 4B had longer spike length as compared to disomic mean indicating the presence of gene(s) increasing spike length on these chromosomes of UP 301. Whereas monosomic populations 1B, 3A, 3B, 3D, 5B and 7D were found to carry genes for reduced spike length. The chromosomes of A and B genomes which have been identified in the present study to carry factors affecting spike length were also reported by BOZZINI and GIORGI (1971) in Tritioum durum variety Capeti. In Sonora-64 chromosomes 3B, 4D and 5D decreased spike length (SHARMA and BHOWAL, 1973) of which only one gene on 3B was identified in the present cross combination. KOSNEV and BARES (1975) associated genes for short spike to chromosomes 3A and 4B. The present study agreed with the results obtained by KOSNEV and BARES (1975) with respect to chromosome 3A which was associated with short spike, but differed with respect to chromosome 4B which is found to carry a gene for increased spike length. Number of tillers per plant shows low heritability (PANIGRAHI, 1962 and SELIM, 1963). Atleast five genes controlled tillering ability differences between Pb. C591 and UP 301. Monosomic populations 3D and 4D had genes for low tiller number per plant, while 2B, 6D and 7B had genes with opposite effects. In the variety Chinese Spring, chromosomes 2B, 3D (SEARS, 1954) and 7B (LAW, 1967) have been associated with high tillering ability. The present study agreed with respect to 2B and 7B, but showed opposite effect for 3D. Thus, chromosome 3D of UP 301 seems to carry many desirable genes affecting morphological characters. |
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