| Chromosomal location of gene(s) for striata mutant
in wheat M.P. JHA and K.M.P. SINGH Indian Agricultural Research Institute, Regional station, Pusa, Bihar, India A classical example of spontaneous chlorophyll mutant is Neatby's virescent gene named after its discoverer (1933). Another natural viable mutant was isolated and described by HERMSEN (1966). SEARS (1957) located Neatby's virescent gene on chromosome 3B of wheat variety Chinese Spring and its near duplicate alleles on 3A and 3D. Interestingly the two recessive genes for Hermsen's virescence were also located on chromosomes 3A and 3B (SEARS and SEARS 1968). However, with the use of chemical mutagens all sorts of chlorophyll mutations are obtained which helped in further understanding of genetics of chlorophyll production. A hemizygous ineffective recessive gene for chlorina - 1 mutant isolated by Shama RAO and SEARS (1964) was located on chromosome 7A of Chinese Spring (SEARS and SEARS 1968). Another chlorina mutant, chlorina 448 was located on chromosome 7B by WASHINGTON (1969). JHA and SINGH (1977) located a dominant gene for another chlorina mutant isolated from the variety Sonora 64 in EMS treatment by VARUGHESE and SWAMINATHAN (1968) on chromosome 7D. The present study was undertaken to locate the chromosomes carrying the genes for yet another type of chlorophyll mutant designated as striata commonly observed after EMS treatment. The mutant used in this study was isolated from the variety Sonora 64 by VARUGHESE and SWAMINATHAN (1968) and is characterised by the longitudinal white (albino) stripe alternating with green area in the leaf right from the seedling stage. The white stripes are relatively more pronounced along the veins. This mutation affects the vigour of the plant although viable seeds are produced. Materials and Methods The materials comprised the striata mutant, the 21 monosomics of the wheat variety Pb C 591, their F1, F2 and F3 progenies, the F1's of striata x chlorina mutants (isolated from the same variety). The striata mutant used as male parent was crossed with cytologically identifled monosomic plants of 21 monosomics and disomic Pb C 591. In addition, reciprocal crosses of striata with parent variety Sonora 64 and chlorina mutant were made. The F1's were grown in 1970-71 at Indian Agricultural Research Institute, New Delhi in pots. Monosomic plants were identified cytologically in each of the 21 monosomic crosses for growing the F2 generation. The F2 populations from the monosomic as well as disomic crosses were grown at Regional Station, Pusa, Bihar in 1971-72. The F3 progenies from randomely selected normal as well as striata plants in F2 were grown in 1972-73. Segregation for striata types was recorded in the seedling stage before the plants were 45 days old. |
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