| Amber grained and awned mutations in wheat variety,
Yaqui-50 Dalmir SINGH, B.C. JOSHI, B. LAL and Jai PRAKASH Division of Genetics, Indian Agricultural Research Institute, New Delhi, India A spring wheat variety Yaqui-50 has been maintaining resistance to wheat rusts for more than 50 years,as reported by CIMMYT, Mexico. For conducting an irradiation experiment, seeds of this variety were obtained from Dr. Raja RAM, CIMMYT, Mexico. This variety is tall, has red kernels and is awnless. Five hundred seeds of Yaqui-50 were irradiated with 30 kR of gamma rays. After irradiation the seeds were planted in the field, In the M1 many chimeras were observed. Fortyfour spikes were observed to be hetero-spelta type and 4 spikes showed homospelta characteristics. Some spikes had spelta type of earhead with awns. No chlorophyll mutations were detected. To raise M2 population, first two tillers were taken from all the M1 plants. Individual spike progenies were sown separately. In the M2 population no detectable chlorophyll deficient mutations were observed indicating that Yaqui-50 may have tetrasomic or hexasomic conditions for chlorophyll synthesis. In all, 3562 plants were screened for isolating amber seeds and awn character. Seven amber seeded and awnless plants were isolated, which were observed in seven different progehies. Eight plants were observed with fully developed awns. Out of these, 6 plants with fully developed awns were from one spike progeny. One plant was observed with amber seeds and fully developed awns. Amber mutants in wheat have been isolated by JAIN et al. (1970) BANSAL et al. (1972) in M1 generation. VARUGHESE and SWAMINATHAN (1967) found amber mutants in M2 generation in the material studied by them. In the present study no amber mutant was detected in M1 generation. In M2 the frequency of amber and awned mutants was found to be comparable. Normal square head spike in T. aestivum is due to the suppression effect of gene (QQ) located on chromosome 5A. In the absence of one chromosome of 5A the spike is spleta suggesting that Q locus is hemizygous ineffective. The F1 chimeras in the present study resemble chromosome 5A deficient spikes. It indicates that one of the 5A chromosome or part of it, where Q locus is situated, got deleted by gamma rays, since the frequency of spelta forming spike is very high. It suggests that physical mutagens, in most of the cases, produce changes by deletion or translocation or due to the loss of full chromosome. |
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