Genetic variation in cultivars of diploid ryegrass,Lolium perenne andL. multiflorum,at five enzyme systems

Summary Samples of approximately 100 plants from each of 22 populations ofLolium perenne representing 15 cultivars, and from 13 populations ofLolium multiflorum representing six cultivars were scored for iso-zyme variants in five enzyme systems, PGI, GOT, ACP, PGM and 6-PGD. From the individual banding patterns a genetic interpretation of the variation was formulated and population studies of the resulting six polymorphic enzyme loci were performed. No strong indications of partial selfing was found since at four of the six loci,Pgi 2, Got 3, Pgm 1 andPgd 1, the genotypic proportions were in correspondence with the Hardy-Weinberg expectations. This indicated, further, that the genetical interpretations of the banding patterns might be correct. Deviations from Hardy-Weinberg proportions forAcp 1 andGot 2 indicated presumably selection working on the linkage group including these loci. Gametic phase disequilibrium was observed betweenPgi 2 andPgd 1 for populations of one cultivar. These results were discussed in relation to the variation expected within a cultivar.     

Control and variation ofin vivo nitrate reductase activity inLolium perenne L. cv. S24

Nitrate reductase activity in leaf material ofLolium perenne L. cv. S24 was estimated using anin vivo assay method such that activity could be estimated at intervals of 5 minutes for up to two hours. The pattern of nitrate reductase activity, as estimated by nitrite accumulation, showed pronounced oscillatory behaviour with frequency of approximately 4 cycles per hour; at certain seasons however oscillatory activity was not shown. The phase of the oscillations observed in different experiments was not co-incident with respect to time of day.     

Control and variation ofin vivo nitrate reductase activity inLolium perenne L. cv S24

Summary Variation in nitrate reductase activity associated with vegetative development and morphological differences inLolium perenne L. cv S24 was examined using anin vivo technique of enzyme assay. Little difference in enzyme activity per unit weight of leaf laminar tissue was found between tillers, between and within leaf laminae but activity in leaf laminae, was much higher than that of leaf sheaths; the activity of shoot material was greater than the apparent root activity. Senescence of leaf material was not accompanied by marked changes invivo nitrate reductase activity.     

Somaclonal variation within poplar

One thousand and ninety-two poplars were regenerated in vitro from callus of 13 poplar clones representing the Leuce, Aigeiros and Tacamahaca sections. At lest 44 of the regenerants differed in some way from the original clones. Somaclonal variation occurred more frequently in poplars of the Leuce section (8%) than in those of the Aigeiros or Tacamahaca sections (1%). Variation was noticed in growth habit, leaf shape or indentation but not in the reaction to four Melampsora races. However, after one growing season in the field, a few regenerants from calli of two clones (Ogy and Rap) differed in their susceptibility vis à vis the original clones. Cultivation of callus from Leuce poplars that had survived exposure to increasing concentrations of toxins from Hypoxylon mammatum gave rise to a toxin-tolerant line from which toxin tolerant plants were regenerated. Flow cytometry to measure the DNA content of nuclei showed that regenerants tended to be tetraploid.Abbreviations NAA naphthaleneacetic acid - BAP benzylaminopurine - TDZ thidiazuron - MS Murashige & Skoog medium     

Somaclonal variation from Sorghum bicolor (L.) Moench cell culture

Plant Cell, Tissue and Organ Culture (PCTOC) - Sorghum bicolor (L.) Moench, plants were regenerated from 4 to 5 month old callus cultures originally derived from seedling explants. Somaclonal...     

Somaclonal variation in high tannin sorghums

Summary Genetic variants were found among over 6,000 primary plants (R₁) regenerated from embryogenic tissue cultures of eight high tannin sorghums [Sorghum bicolor (L.) Moench]. Field assessment of somaclonal variation has progressed to the R₂ population, with over 48,000 R₂ seedlings (27,000 plants) in 1,126 rows from 1,055 R₁ plants. A total of 43 variant phenotypes was recovered, including several types of chlorophyll deficiencies, dwarfism, short culm, sterility, narrow leaf, and several previously unreported variants, such as ragged leaf, multibranched heads, and Hydra, a developmental variant which produces large numbers of panicles. Variation production greatly depends on parent genotype and appears to increase with increasing time in cultures. The toal average somaclonal variation rate (based per 100 R₁ plants) and somaclonal variant frequency (based per 100 R₂ plants) estimated in the tested population were 11.3 and 1.6, respectively. Chimerism was found in regenerants. The estimated size of the mutated sector carried by mutant regenerants ranged from the whole plant to less than 3% of a single head. The average proportion of mutated R₁ heads carrying large (80%–100%), medium (40%–80%), and small (<40%) mutated sectors was 38.7%, 26.0% and 35.3%, respectively. Some sector mutations do not appear until the R₃ generation. In order to avoid losing variants, the population for selecting somaclonal variation should be as large as possible. Some of these variants found may be useful for further study or for use in breeding programs.     

Allozyme variation within and between populations inLolium (Poaceae)

Isozyme analysis was used to determine genetic variation within and between populations of sevenLolium species. All populations from the inbreeding species (L. temulentum, L. remotum, L. loliaceum, andL. persicum) were completely fixed for all enzymes scored. They also contained, for four of the five enzyme systems studied, exactly the same allelic variant. The three cross-breeding species showed large within-population variation and much less between-population variation. The great similarity of the allozymic variants found in all species, made the division of the genusLolium into species on basis of allozymic data difficult. It was not possible to separate the different inbreeding species from each other. Within the cross-breeding groupL. multiflorum andL. rigidum could be distinguished fromL. perenne. L. multiflorum, andL. rigidum could, with more difficulty, also be separated from each other. Allelic variation could have more relation with the provenance of the populations than with taxonomic classification.Genetic variation inLolium spp. II. For first part see Pl. Syst. Evol. 188: 87–99.     

Somaclonal variation versus chemically induced mutagenesis in tomato (Lycopersicon esculentum L.)

Summary A comparison was made of the type and frequency of mutational events found in the progeny of tomato plants regenerated after one passage in vitro with those induced by chemical mutagenesis with ethyl methane sulphonate. Several mutants were recovered in the progeny of regenerated and mutagenized plants of two cultivars of tomato. They can be grouped into the following categories: seedling lethality, male sterility, resistance to Verticillium, short stature, change in number of lateral shoots or in leaf shape. The results indicate that the two sources of variability differ in their effect, changing the spectrum and frequency of the mutants as well as, at least in some cases, their pattern of segregation.     

The typification of Lolium perenne L. and Loliutn temulentum L. (Poaceae)

LOOS, B. P. & JARVIS, C. E., 1992. The typification of Lolium perenne and Lolium temulentum (Poaceae). The typification of the Linnaean species Lolium perenne and Lolium temulentum has been studied. Lolium perenne is typified by material in LINN, as proposed by Terrell, but it has been necessary to select a lectotype for L. temulentum , and material in the Burser herbarium (UPS) has been chosen for this purpose. The study shows that although Linnaeus used awns as a diagnostic character to distinguish the two species, he was aware of the intraspecific variability in this character.