Elementary Genetics, p. 320-322 (1962)
W. Ralph Singleton

Mutagenicity of Peanut, Mustard, and Castor Oil on Cereals

An interesting experiment on the mutagenicity of some of the common vegetable oils, castor oil, mustard oil, and peanut oil was performed by Swaminathan and Natarajan in India (1959). They observed that it was common knowledge that some species with a high concentration of oil in the seed were more resistant to the effects of radiation than other species like the cereals, with low oil content. They reasoned that the cereals might be more resistant if soaked in vegetable oils.

After the seeds were soaked in either castor, mustard, or peanut oil, they were germinated in sand. The results were startling. Instead of the oils imparting resistance to the cereals after radiation, the oils themselves caused a marked decrease in germination of the seeds. In addition, in root tips, also at meiosis, a high percentage of chromosomal irregularities were induced, as well as several mutations in the bread wheats (grown to maturity).

The reduction in germination was more pronounced in the species with the lower chromosome numbers, Triticum monococcum (n=7) and T. dicoccum (n=14). For example, germination was completely inhibited in T. monococcum by soaking six hours in peanut oil, while T. dicoccum (Emmer) showed only 38% germination. However, the bread wheat T. aestivum (n=21) had 46% germination after soaking not six, but 24, hours in peanut oil. The bread wheat was the only species in which mutations were induced.

The amazing discovery was that the mutation rate induced in T. aestivum by peanut oil was higher than that produced by X rays, fast neutrons, P32 and S35, nitrogen mustard, and the other vegetable oils used. The mutation frequency was 156% per plant progeny. Some of the mutant characters induced are shown in Fig. 17-17. Castor oil produced 61% and mustard oil 4% per plant progeny.

Recently two research workers at Washington State University, C. F. Konzak and R. A. Nilan, discovered that one chemical, diethyl sulfate, produces genetic changes in barley without the concomitant chromosomal breakage usually accompanying such changes. This chemical and others under investigation may prove to be something that geneticists have been hunting for a long time—a mutagenic agent that can produce gene changes without breaking chromosomes.

Fig. 17-17 Earhead variations in the second generation of wheat plants grown from seed treated in oil. Above: (1) Reduced awns in the lower spikelets (castor oil), (2) long tipped (castor oil), (3) red glume (peanut oil), (4) red glume-speltoid (peanut oil), (5) speltoid (mustard oil), (6) lax (castor oil), (7) dense spike of erectoid mutant (peanut oil), (8) beardless mutant (peanut oil). Below: Control (extreme left) and erectoid mutants.

J Hered (1959) 50 (4): 177-187. (July 1959)
Cytological and Genetic Changes Induced by Vegetable Oils in Triticum
M. S. Swaminathan and A. T. Natarajan*

*Cytogeneticist and Assistant Cytogeneticist respectively, Indian Agricultural Research Institute, New Delhi-12, India. The authors arc grateful to Dr B. P. Pal and S. M. Sikka for their advice and interest in the study. They are also indebted to Dr. E. R. Sears of the Missouri Agricultural Experiment Station and Dr. J. MacKey of the Swedish Seed Association, Svalöf, for their kind help in interpreting the data relating to the awn mutation.

DURING the course of the mutation experiments carried out at this Institute in several crop plants, the earlier findings of Gustafsson8 and other workers that there are marked differences in sensitivity to radiations among different plant species were confirmed. It was found that some oilseed plants like linseed and mustard are much less sensitive to radiation with X-rays and β-particles from P32 and S35 thin cereals such as wheat and paddy. It seemed likely that the presence of oils in seeds might have a buffering effect on radiation and in an experiment designed to elicit information on this problem, seeds of Triticum monococcum, T. aestivum, Oryzi sativa and Vicia faba were first soaked in some vegetable oils and edible fats, and later subjected to X-irradiation. In this experiment, controls with no treatment and with seeds soaked in oils for various durations but not subsequently irradiated were kept. Observations on preparations of root tip mitosis made from this material showed that immersion of seeds in oil alone caused chromosome breakage in many cells21. Following this finding, a detailed study of the cytological and genetic effects of treatment with oils on Triticum species was undertaken, in an "Allium test" (Levan11) carried out during the earlier study, oils extracted from peanut (Arachis hypogaea), castor (Ricinus communis) and mustard (Brassica campestris var. toria) had been found to induce the highest frequency of chromosome aberrations and these three oils were therefore included in the present experiment.

Materials and Methods

Dry seeds of einkorn (T. monococcum var. Japanese Early; 2n = 14), emmer (T. dicoccum, var. Khapli; 2n = 28) and bread wheat (T. aestivum var. C. 391 ; 2n = 42) were soaked during the crop season of 1956, in peanut, mustard and castor ails extracted at the Division of Chemistry of this Institute. Seeds of einkorn and emmer wheats were soaked for six hours and the treatment lasted for 24 hours in bread wheat. At the end of the treatment, the seeds were wiped well with a muslin cloth and sown in the field. A few seeds were germinated in petri dishes for the study of root tip mitosis. The root tips were fixed for 24 hours in acetic-alcohol (1:3) and were stained in leucobasic fuchsin after acid hydrolysis. Microsporogenesis was studied in Feulgen squashes. Preparations were also made from control plants raised from seeds sown either dry or after presoaking in water. Seeds of all treated plants were collected separately and the individual plant progenies were raised during 1957. Morphological observations were recorded both in the year of treatment and during the second generation.

Results

Germination of seeds

The percentage of germination in different treatments is given in Table I. Control seeds showed 96 to 100 percent germination. From the data, it is seen that in T. monococcum and T. aestivum, treatment with peanut oil, caused the greatest reduction in germination. The