| I. Research Notes Cytogenetics of branched spike in bread wheat Dalmir SINGH and B.C. JOSHI Indian Agricultural Research Institute, New Delhi-110012,India. Utilising chromosome 5B manipulations, JOSHI & SINGH (1979), have been able to transfer several desirable traits from rye into bread wheat.One single cross of hexaploid wheat variety PbC591 x ryes has generated enormous variability. A Iine from this material was segregating for normal and branched ear heads. It was observed that there were 5 plants which had branched ear-heads. The plants having branched spikes as well as the plants possessing normal spikes were picked up for further study. All the spikes of these plants were selfed. Spikes were taken from branched as well as normal plants for meiotic studies. Observations at first meiotic metaphase revealed that all the plants producing branched ear-heads were trisomics (2n=43) and normal looking plants were disomics (2n=42). A regular trivalent was observed in a large number of cells of ramificated spikes while meiosis in disomics showed regular 21 bivalents. Seeds obtained from branched and normal spikes, after selfing, were sown as spike progenies in the field to study the breeding behaviour of ramification. Normal spiked progenies produced only normal type of plants. Progenies of all the branched spikes segregated for branched type as well as normal type of spikes. A total of 253 plants were observed. Out of these, 230 were normal spiked while 23 were branched type. Meiotically all the branched plants were found to carry 43 chromosomes with a trivalent and normal plants with 42 chromosomes showed regular 21 bivalents. Spikelet number in normal spikes ranged from 23 to 25 while in branched spikes the range observed was 75 to 87. Ramificated plants were 60-70 cms tall and normal plants were 90 to 100 cms tall. Branching in the spikes of Triticum has been reported in derivatives of inter-varietal crosses by KORIC (1967, 1971, 1974, 1978), interspecific and intergeneric crosses by SHARMAN (1944), TSITSIN (1965) and as induced mutations by SWAMINATHAN et al. (1966). Occurrence of ramificated spikes of Triticum aestivum Var. NP797 in an M2 population might have resulted from a deletion as suggested by SWAMINATHAN et al. (1966). KORIC (1978) proposed two genes, ramifera (Rm) and tetrastichon (Ts) for ramification . He suggested that ramification is the product of complementary gene action of Rm and Ts genes. On the basis of meiotic studies of ramificated spikes (2n=43), which showed a trivalent in majority of the cells, it is suggested that ramification in Triticum aestivum in the present case may be as a result of additional gene dosage due to trisomic condition. Identification of the chromosomes involved in the trivalent is in progress. |
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