Section 5 — Mutagenesis 



more irradiated as seedlings with 300 r. From 

 every plant 59-158 progenies were grown total- 

 ling 1488. 237 mutations appeared among them. 

 The mutation spectra of the 14 X°-plants were 

 quite different, because 19 phenotypes repeatedly 

 emerging were not distributed at random, but 

 accumulated within closely related strains. 6 of 

 the phenotypes appeared 2-4 times within the 

 progenies of a single Xo-plant, 9 others were 

 detected among kindred plants. In addition mu- 

 tations appeared in mendelian proportions of the 

 progenies as a result of the first irradiation. These 

 mutations of course were not included in these 

 dates. The first radiation experiment yielded 

 similar results with respect to the mutation spec- 

 tra as the second one did. Coincidences so fre- 

 quently occurring cannot be due to mere chance; 

 therefore the conclusion must be drawn that 

 some of the loci in different strains excelled above 

 the others in their particular disposition for 

 mutations. 



5.118. Effects of Ionizing Radiations on Cucumis 

 sativus L. and Momordica charantia L. Filo- 

 mena, F. Campos and Walderico M. Gene- 

 roso (Laguna, Philippines). 



Results obtained from subjecting seeds of 

 Momordica charantia L. and Cucumis sativus L. 

 to various levels of X-rays and r-rays showed 

 that germination was relatively unaffected. How- 

 ever, differences in the relative sensitivity of cuc- 

 umber seeds to X-rays and r-rays were observed. 

 Xi and Ri seedlings of both species beyond 15 

 kr exhibited chlorophyll and morphological 

 abnormalities. Significant differences between do- 

 sages were observed when analysis was based 

 on growth of the plants in terms of length of 

 the main vine. Regardless of treatment, days to 

 floweringwas relatively unaffected by irradiations. 



In Momordica there was an increase in the 

 proportions of male to female flowers in the 

 X-ray series but none in the Co 60 series. On the 

 other hand, sex ratio in cucumber was not altered 

 by irradiation although reductions in the number 

 of male and female flowers were noted. Sex 

 reversion was observed only in Momordica plants 

 on the treated and segregating generations. Two 

 types of sex-reversed flower were observed. 



Seedling mutations observed in the X2 and R2 

 generations were mostly chlorophyll abnormali- 

 ties. However, a few clear-cut morphological 

 abnormalities were detected. A few mutations 

 having no conspicuous effect in the seedling stage 

 but causing distinct variations in the later devel- 

 opment are also included. 



5.119. New Mutations Obtained in Vicia faba L, 

 through the Injection of Chemicals. Pierre 

 Bryssine (Rabat, Morocco). 



Sundry chemicals were injected by means of a 

 hypodermic syringe into the hollow inside the 

 stem of V. faba L. 



The chemicals, though extremely toxic and 

 injected at considerable rates (10-30 ml per stem), 

 are rapidly absorbed by the tissues. The conse- 

 cutive depressive effect was evaluated from the 

 variation of the production of pods (number) 

 and seeds (weight and number). 



Considerable changes were observed on the 

 treated plants: sterility, growth disorders, fascia- 

 tion, chlorosis and variegation of the foliage, 

 dichotomy of branches, anarchic proliferation of 

 medullary tissues, disorders of the vascular 

 system, etc. 



From Ci onward several types of mutants 

 could be observed concerning: 



(a) The vegetative system (growth habit, bran- 

 ching type, shape of leaf, chlorophyll defi- 

 ciency, etc.) 



(b) The pods (shape, size, pubescence) 



(c) The seeds (size, shape, colour of seed coat 

 and hilum) 



Attention is drawn to the rare or hitherto 

 unknown forms among these mutants (from C2 

 and C3 onward): 



1. Geant (stems of more than 2 m with long 

 internodes) 



2. Unifoliolata (with a single leaflet) 



3. With tendrils (lanceolate leaflets, branched 

 tendrils) 



4. Begonia (prostrate plants with very thick 

 leaves) 



5. Wild (dwarfed erect plants with small seeds) 

 As to the experienced chemicals, the best re- 

 sults were obtained with mitoclasic materials (at 

 high concentrations: colchicin, acenaphthene, 

 gamma-hexachlorocyclohexane) as well as with 

 extracts of old seed (tobacco, soya, chick-pea). 

 Methane-sulfonate-ethyl and acetone equally 

 proved very interesting. 



The advantage of the injection method is dis- 

 cussed. 



5.120. Radiation-induced Reversions to Prototrophy 

 in Tryptophan-requiring Escherichia coli WP2 

 B. A. Bridges and R. J. Munson (Berkshire, 

 Great Britain). 



We have attempted to follow gene duplication 

 in populations of Escherichia coli B/r (strain WP2, 

 tryptophan-requiring) by irradiating at intervals 

 during synchronous nuclear replication. A late 



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