| The results indicated that eleven chromosomes namely 1B, 2A, 2B, 2D, 3B,
3D, 4A, 4B, 6A, 6B and 7A in Mex. C.B. 116 and five chromosomes 1B, 2B,
2D, 3A and 3B in variety Hira increased the average number of ears per plant.
It was interesting to notice that none of the F2 monosomic population
showed any significant reduction in the ear number per plant. SEARS (1954)
observed that chromosomes 1B, 1D, 2A, 2B, 2D, 3B, 4B, 5D and 6A influenced
this character, but their expression was variable. TSUNEWAKI & HEYNE (1959)
reported all members of homoeologous group 4 and LAW (1966) associated chromosomes
1B, 3A, and 3D which distinctly influenced ears number per plant. SHARMA
and BHOWAL (1973) attributed the increase in spike number per plant to the
absence of chromosomes 4A, 4B and 7A, where as they found decrease was due
to the absence of 2B and 4D chromosomes. BHAT & GOUD (1979) reported that
monosomic population 3D and 4D had genes for low tiller number per plant,
while 2B, 6D and 7B had genes with opposite effects. The comparative observations have indicated that chromosomes namely, all members of 1, 3, 4 and 7 homoeologous and 2A, 2B, 5A, 5B and 6A showed variable range of reduction in the mean number of spikelets in variety Mex. C.B. 116. In variety Hira, eight F2 monosomic lines (1A, 1D, 2B, 4B, 5B, 6B, 7A and 7D) had less number of spikelets. This finding is in agreement with previous reports on this trait (SASAKI et al. 1968; SHARMA & BHOWAL 1973). In addition, six chromosomes, 2A, 3A, 4A, 5A and 5B are reported for their effects on number of spikelets. Joint consideration of the characters, spikelets per ear and grains per ear, revealed that most of the chromosomes like 1A, 1B, 1D, 2A, 2B, 3A, 3B, 4A, 4B, 4D and 5B in variety Mex. C.B. 116 and chromosomes like 2B, 4B, 5B and 7A in variety Hira are responsible for reducing the spikelets per ears as well as grains per ear. But the genes located on the other chromosomes are not similar for the visual expression of both the characters. Among these chromosomes, some are responsible for spikelets per ear, while other's effect is confined to the grains per ear. On the basis of these observations, it can be suggested that there is some independence between these two characters, and different genotypes appear to have different chromosomes involved. |
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