Showing papers in "Canadian journal of genetics and cytology in 1962"

The cytogenetics of lotus. i. embryo-cultured interspecific diploid hybrids closely related to l. corniculatus l

Abstract: Introduction The genus Lotz~s of the tribe Loteae contains a heterogeneous assemblagc of annual and perennial species numbering close to 200 (Larsen, 1958). There are two principle geographic centers of origin of the species, namely, the Mediterranean region (Hertzsch, 1959) and Western North America (Nlunz and Keclt, 1959). A few endemic species are found in Australia, Japan, and North Africa (Brand, 1898). The range of soine species has been gfeatly extended by man, for exan~ple, several agronomically interesting species of European origin (of which L. conzicz~latz~s L. and L. 71zajor Scop. (syn. L. ~~ligi~zosz~s Schltuhr) are most widely cultivated) are now well established in North Africa, New Zealand, Australia and on the American continent as forage crops (I Hertzsch, 1959). Chron~oson~e numbers determined for different species (2n = 12, 14, 24, 28) indicate that a polyploid series with two basic chron~osome nuinbers (i.e., x = 6 and 7) exists within the genus (Darlington and Wylie, 1955; unpublished observations).

Cytogenetic studies in the genus hordeum vi. the murinum-complex

Abstract: Horclez~nt 7~zzni1zz~nq, the ubiquitous species common to most of Europe and Western Asia, call also be found in many parts of North and South America and Australia. It and two other species, H. lepori~zuwz, another tetraploid, and H . glnucz~~n, a diploid, all having remarltably similar morphological features, are frequently referred to as the murhzz~m-complex (Covas, 1949, and Morrison, 1958). In 1960 W. M. Bowden, Plant Research Institute, Ottawa, received seed samples labelled H. nzz~rinz~m from Turlcey and Afghanistan which had 2n = 42 cl~romoson~es. This new form increased the number of species in the con~plex to four and the chromosonle number to the hexaploid level. The most striking feature of the coinplex is that the plants look very much alike. Therc has, therefore, been much confusion in classification although there are minor differences as shown by IVlorrison (1958). H e also clearly showed that both H . ~ ? T z L ~ ~ ' I ~ z L ~ ~ z and H . leporhzum are allotetraploids. Previous lists of chromoson~e numbers had indicated that H. 7mninum was a diploid (Hubbard 1954), an error that led Covas (1949) to propose that H. lepori1zzr7/1 was an allotetraploid derivative of H. glaz~cz~nz and H. muri7zzmz. The purpose of this study is to clarify the status of the various species, to learn about their interrelationships and to find genetical explanation for thc inorpl~ological uniformity of species in the complex. This is also the first paper in this series which deals with a group of Old World species of Hordenzuz. Since the approach is primarily cytogenetic, hybrids were produced among the four species to study their infertility and chromosome relationships.

Irradiation-induced chromosome aberrations in normal human leukocytes in culture.

Abstract: An investigation of irradiation-induced chromosome aberrations in human leukocytes in short-term culture is described. In the production of one-hit aberrations there appeared to be a linear response to dose, but no dose-rate effect. The data were compatible with either a linear or a possible power- function relationship between dose and aberration frequency in the production of two-hit aberrations. The small sample size was considered to be the most probable explanation for this lack of discrimination. A defintte dose-rate response was observed in the production of twohit aberrations, the larger number being produced at the higher dose-rate. It is difficult to compare induction rates as derived from different laboratories, owing possibly to differert methods of scoring, and also to attempt to derive break-rates'' by combining one-hit and two-hit aberration data. Because of a definite dose-rate effect on the production of two-hit aberrations, and also because these are expected to occur as a power-function of the dose, induction rates might more properly be calculated for each type of aberration separately. These studies indicate that irradiation-induced polyploidy follows from the initial induction of endoreduplication. The chromosome pairs of the endoreduplicated cells appear to fall apart at the first mitotic division following diplochromosome induction,more » to result in tetraploid daughter cells. Short-term cultures of human leukocytes provide a satisfactory system in which to examine irradiation effects. (auth)« less

Chromosomes involved in translocations obtained from haploids of common wheat

Abstract: Introduction The haploid chron~osome complenlent of common wheat, Triticz~m crestivum L., is made up of three genomes, designated A, 73, and D. Each genome consists of seven chron~osonles and corresponds to the haploid conlplen~ent of a related, inore primitive species from which it was presun~ably acquired. T h e A genome comes from einltorn wheat, the D genome coines from Aegilops squmrosn L. (McFadden and Sears, 1914; Kihara, 1944), and the B genome ome fro111 Ae. speltoides Tausch (Sarltar and Stebbins, Chapman, 1958). among genomes A, B, and D have been studied by obhavior of chromosomes in F, hybrids anlong the parental Lilienfeld, 1932, 1934; Sears, 1941; McFadden and Sears, ) and in haploids of einltorn (Kihara and Katayama, 1932; hara and Yainashita, 1938; Smith, 1946), enlnler (Kihara, wheat (Gaines and Aase, 1926; Yamasalti, 1934, 1936; ars, unpublished; Krishnaswamy, 1939; i\/IcGiilnis and Unrau, 1952; Person, 1955; Riley and Chapman, 1957). These studies, IIO\Vever, have not given specific infirmation as to which chron~osomes of the three genomes associate with each other at meiosis o r as to whether chromosonle pairing is intraor intergenomic, because the wheat chroinoso~nes are all metacentric or nearly inetacentric and cannot be distinguished from each other

MUTATION FREQUENCIES IN BARLEY AFTER TREATMENT WITH γ-RADIATION, ETHYLENE IMINE, ETHYL METHANESULFONATE AND MALEIC HYDRAZIDE

Abstract: The frequency of mutations affecting chloroplastids and their pigments in barley after treatment with gamma -radiation, ethylene imine, ethyl methanesulfonate and maleic hydrazide was investigated. Some combinations of chemicals or of chemicals and radiation were also used. Of 14,000 spikes of untreated barley only 11 had new chlorophyll mutations. The mutation frequency per spike was 0.0007. When dry grains were irradiated with small doses of gamma -rays the results indicated that the doubling dose was in the 25 to 100 r range. With the largest radiation dose, 10,800 r, the mutation frequency per 100 spikes was 6.1. The effectiveness of each r of dose in inducing transmissible mutations appeared to decline as the dose was increased. Seeds soaked in adenine-thymine solutions for some hours before and after irradiation yielded fewer mutations than did irradiated water-soaked seeds. The highest mutation frequency obtained in experiments with ethylene imine alone was 20.5%. When seeds were treated with both ethylene imine and adenine thymine solutions the mutation frequency rose to 23.8%. These substances when combined may have a synergistic effect. Ethyl methanesulfonate was the most effective of the tested mutagens, giving a maximal frequency of 39.8% mutant spikes. Maleic hydrazide solutions induced very fewmore » mutations in the embryos of barley seeds. The compound exerted a slight protective effect when applied prior to gamma -irradiation treatment.« less

The sex chromosome constitution of chironomid intersexes parasitized by nematodes

Abstract: Intersexuality in Cliironomidae induced by nematode parasitism is a relatively comn~on phenomenon. Thus Wiillter ( 1961) found that in Tmzytarsus larvae the ,percentage of parasitism may approach one hundred. Townes (1915) observed that in C13ir01zo7nzrs ~ I Z L I ? Z O S Z L S more than 25 per cent may be intersexes. A summary of the literature on this subject is given by Wiilker ( 1961) and Thienemann (1951). Rempel (1940) made an extensive study of the plienoiuenon in a species identified as C. hygerborezrs Staeg. Because the typical intersexual form possessed a female body and a inale hypopygiuin he concluded that the intersex is "a female which through a loss of its reproductive glands has developed male external genitalia, and a male reproductive duct." H e based his conclusion largely on the following: unparasitized chironoillid larvae near pupation show a marlted sexual difference in size, the female larva being larger than the male larva; parasitized larvae are frequently larger than normal male larvae; the adult intersex is largely a female. Although it was difficult to explain how a genetically female individual could develop a illale hypopygiun~ in all its details, it would have been infinitely more difficult to explain how a genetically male larva could retain its normal reproductive system and build around it a female body. When this study was conducted (1936) it was impossible to separate the sexes of the larvae on the basis of the chromosomal con~plen~ent (Bauer, 1935, 1936; Gilchrist and Haldane, 1917; Beerniann, 1955). Recently Beermann (1955a) showed that in Cnnrptochiro~zonzzrs tentnus, C. pnllidivithtus and Chiro1z07nns annz~lnr-iz~s it \vas possible to determine the sex of larvae on the basis of salivary gland chromosomes. IViilker (1961) then demonstrated that in cliironomids, male and female larvae are subject to parasitism by nematodes to an equal degree, and that the former, i.e. infected $male larvae, develop into the typical intersex (Gonopoden-Intersex, female body and male genitalia) and the latter into females in which the 8th sternum mav show a tendencv toward maleness J J (Sternit-Intersex). Since these findings are in contradiction to those of Rempel, it seemed desirable to reexamine the latter's findings. The original investigations were conducted with a species identified as Chiro7zonzus hyperboreus Staeg. Thienemann (1942) showed that the Canadian form could not be identified with the European form under that name and he assigned it a new name, C. rmzpelii. Townes (1945) called the latter C. anthracinzes Zett., but Thienemann (1954) pointed out that C. nnthrncinus belongs to the thumnzi-bathophilus groups, while C. rempelii belongs to the plumosus group. Also, Wiilker (1961) stated that a sex-chromosome inversion has not

Inheritance of winterhardiness in an eighteen-parent diallel cross of barley

Abstract: Introduction Since winter barleys generally produce higher grain yields than spring barleys, under conditions of little or no winterkill, plant breeders have been in search of winter hardy varieties that would permit a northern expansion of the crop. This search has not uncovered varietal material appreciably superior to winterhardy varieties already in commercial use. Attention of plant breeders has, therefore, been directed toward hybridization and concomitant genetic problems with the view of combining characteristics of several varieties into new types of higher winterhardiness. Pulham (1954) and Rohde and Pulham (1960) made diallel crosses between eighteen varieties of winter barley and studied winter-survival behavior of all F1 and F., progenies and of the original eighteen varieties. In revie~t~ing this work, the present authors noted that the full diallel techniques had not been followed in analysing the data. Rhode and Pulham (1960) consolidated the data of all experinients and calculated total variance, treatment variance, error variance etc.; but they did not separate the different components of variation, such as Ileritable-fixable, Ileritable-nonfixable and nonheritable variation, nor did they study how these interact in the expression of the character. I t was felt, therefore, that it might be profitable to re-analyse the data using thc diallel techniques of Hayman ( 1 951). Accordingly, the original ra\v data were obtained from Dr. ~ o h d e for inspection. The results of the re-analysis of these data are reported and discussed in the present paper.

The effect of maternal age and radiation on the rate of non-disjunction in Drosophila melanogaster.

Abstract: The effects of maternal age and radiation on the rate of non-disjunction of X chromosomes of Drosophila melanogaster aged from one to 29 days before mating was studied. In the absence of radiation there was no detectable effect of maternal age on the frequency of XO and XXY progeny in Drosophila melanogaster. With irradiation, however, there was, in addition to an overall increase, a significant effect of maternal age. Females who were older at the time of irradiation produced more exceptional progeny, in agreement with previous results. (P.C.H.)

A morphological study of the x-ray induced cauliflower-head and single-leaf mutation in medicago sativa l.

Abstract: The morphology of a spontaneous and an x-ray induced cauliflower-head and single-leaf mutation was compared with normal alfalia. Chromosome numbers were 32 in the normal and the spontaneous mutation, 31 in some, but not all, of the x-ray induced lines. The cauliflower mutant was unrelated to the trisomic tetraploid condition of the B45 line. Flower development in x-ray-induced cauliflowerhead was restricted to profusely branched floral axes that produced only meristem primordia, and under treatment with gibberellic acid, rudimentary pistils, but no stamens, petals, or sepals. Flower development in the spontaneous mutation showed sparingly branched floral axes, which produced rudimentary pistils and linear bracts homologous with sepal-petal primordia. With gibberellic acid treatment, pistil development approached normal, but no stamens, petals, or sepals were produced. Leaf development, which is triioliate in normal alfalfa, was unifoliate in both mutants. The uniioliate leaf appeared to result iron suppression of lateral leaflet primordia. The results suggest that the x-ray induced mutation, although similar, is more extreme and rudimentary, in tissue differentiation, than the spontaneous mutation. (P.C.H.)