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Brettell d al. (1986) analyzed regenerated Triticale plants for changes in rRNA genes located<br />

at the siie of nucldar organlm regions (the Nor loci) in chromorome 18, 6B and 1R and<br />

found reduction in the rDNA units. The reduction in the 1R rDNA spacer sequences was<br />

heritable and correlated wlth reduced c-banding at the position of Nor-R1 on chromosome<br />

1 R. Lapltan et al. (1988) also reported arnpliiication of DNA In Trificale. Both amplification and<br />

dearnpllfication of DNA sequences among callus cuHures ol maize were reported by Brown<br />

et ai. (1991).<br />

In sugarcane Heinz and Mee (1971) detected metabolic differences which rnighl not atfed<br />

morphological characteristics on Obse~ing the isozyrne patierns of esterase, peroxidote,<br />

amylase and transaminase. 75% of the 53% ol regenerants which showed morphological<br />

variations revealed isozyrne dfflerences.<br />

In alfalfa Baertlein and McDaniel (1987) observed 9.1% of plants regenerated horn callus to<br />

be significantly dilferent hom the parent and from the other somaclones as judged horn the<br />

quantitative protein pattern. Somaclones were grouped according to linkoge b ed on<br />

protein electrophoresis pattern. Two showed non-overlap with parental grouping indicating<br />

significant molecular divergence.<br />

2.22 MllOCHoNDRlAl DNA VARIAllON<br />

Many authors have investigated mitochondrlal DNA (rnt DNA) variability in tissue cultured<br />

plants. Urnbeck and Gengenbach (1983) observed the absence d a 6.6 kb mitochondtial<br />

DNA hagment in Idle varlant llnes regeneraled from a culture of a Texas mde rkrile<br />

cytoplasm mdre. Thk 6.6 kb lmgmnt k blhved to bo involved In Me male-steflle toxin-<br />

susceptible phenotype. McNay st al., (1984) 0bsow.d minor changes In the rnt DNA d moire

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