Comparison of the Effect of X-rays (Soft X-rays) on the Production of Mutation in Diploid and Tetraploid Species of Phalaris

Abstract

Dry dormant seeds of Phalaris canariensis Linn. (2n=12) and Phalayis minor Retz. (2n=28) were irradiated with 10 Kr. soft X-rays at the M.R.C. Unit, Hammersmith Hosptial, London and its effect on the production of chlorophyll, and morphological mutants at M₂ generation have been studied and discussed in both the species.
In Phalaris canariensis Linn., the usual chlorophyll mutants, virescens, chlorina, lutescens, albino, tigrina, virido-albino and maculata were seen at seedling stage. Viridis was found to be most common and maculata to be rare. When viridis was broken up into different types on the basis of colouration, lutescens is commoner than virescens and chlorina which are present in almost equal numbers.
The frequency of mutants varies from 0.22-4.5. This was determined per 100 M₂ seedlings (Gaul 1960) and was found to be higher at the low fertility range. No mutants were seen between the 71 and 90% fertility classes.
Morphological mutants of the type, split and appendage on the margin of the leaf, split on the margin and lamina, appendage on the margin, trifid and bifid apex, rudimentary leaf, leafless, twisted and pendulate rachis and whitehead, tweaky, multiflorous, impeded, white-green and spikeless infloresence have been observed in P. canayiensis.
No chlorophyll and morphological mutants were seen in P. minor inspite of 19, 708 seedlings tested.
The appearance of chlorophyll and morphological mutants at M₂ generation in the diploid species P. canariensis (2n=12) suggest that they are more sensitive to radiation than the tetraploid P. minor (2n=28).