Intra-varietal Variation Research Articles

Intravarietal variation in satellites and C-banded chromosomes of Agropyron intermedium ssp. trichophorum cv. Greenleaf

A high amount of intravarietal variation in satellites and C-banded chromosomes was observed in the hexaploid wheatgrass synthetic cultivar 'Greenleaf' (Agropyron intermedium ssp. trichophorum (Link) A. &Gr., 2n = 6x = 42, genome E1E1E2E2SS). The cultivar is an open-pollinated perennial that shows extensive interplant polymorphism for many biological characters. Maximum number of satellites detected varied among plants from zero to six. In 61% of the plants, we observed two large satellites in association with zero, one, or two small ones. Chromosome constitution differed significantly among plants as revealed by analysis of variance based on the total number of banded chromosomes and the number of banded chromosomes with telomeric bands at either one or both ends. Heteromorphism in C-banding patterns between homologues was found in most of the chromosomes and was classified into four types: (i) difference in band size, (ii) difference in presence/absence of one or two bands, (iii) completely different banding patterns, and (iv) banded versus unbanded. Homologous chromosomes having types iii and iv heteromorphism could only be matched by their relative length and arm ratio instead of C-banding patterns. Deletions were detected in two chromosomes. Overall, C-banded chromosomes of this cultivar were characterized by the presence of large telomeric bands and were quite different from the previously reported karyotypes of the supposed diploid ancestor Agropyron elongatum (Host) P. Beauv. (genome EE) and an Ag. intermedium (Host) P. Beauv. accession (E1E1E2E2SS) The results suggest that dramatic chromosome modifications have occurred in this species during the course of evolution. The study sheds light on the extent of intrapopulation polymorphism present in the karyotypes of outcrossing polyploids and synthetic cultivars and has implications regarding strategies for chromosomal manipulation involving open-pollinated species.

Minimizing Intravarietal Variation in Rice Experiments

Minimizing Intravarietal Variation in Rice Experiments

K m values of ribulose-1,5-bisphosphate carboxylase of cassava cultivars

Ribulose-1,5-bisphosphate (RuBP) carboxylase activities of two cassava cultivars increased with leaf age but their K m(CO 2) and K m(RuBP) values remained relatively constant. K m(CO 2) values of 16 cassava cultivars ranged from 7.8 to 14.0 μM CO 2, while K m(RuBP) values varied from 7.5 to 24.8 μM RuBP. Differences in the K m values could not be attributed to different physiological ages of plant material or to intravarietal variation, and are more likely to have been inherited. The results also showed that K m values have potential applications in cassava systematics.

Intra-varietal variation for in vitro plant regeneration in the genus Trifolium

Seedlings of Trifolium repens showed considerable variation with regard to the morphology and growth of their calli, and their ability for in vitro differentiation of shoots. One of the lines selected for regeneration in primary callus cultures also showed shoot formation from protoplasts. Somatic embryogenesis in callus cultures of T. pratense and T. arvense occurred only in selected seedling lines. This paper highlights the importance of screening a large number of plants within a cultivar of outbreeding species to achieve reproducible plant regeneration from tissue culture.

Intravarietal variation of heading dates among foreign rice cultivars

Intravarietal variation of heading dates among foreign rice cultivars

Amylase isozymes of oats (Avena sativa L.)

AbstractAmylase isozymes were studied in six varieties of Avena sativa L. using agar gel electrophoresis. Three distinct zymograms were detected in aqueous extracts of endosperm of 4 to 5‐day old seedlings. No intravarietal variation was observed. These results indicate that amylase zymograms may be useful markers for helping in the identification of oat varieties. Using the varieties Maris Tabard and Maris Titan it was found that all the isozymes in 4 to 5‐day old seedlings, except one, had the properties of α‐amylase. The zymograms of extracts from ungerminated grains of these two varieties, although apparently identical to those of 4 to 5‐day old seedlings, differed in that all the α‐isozymes in the former were found to be heat labile whereas in the latter they were heat stable.

Infection of Lolium and Festuca spp. by Drechslera siccans and D. Catenaria

Drechslera siccans was the commonest of the species of this leaf spot pathogen found on single spaced plants of Lolium perenne at Aberystwyth. D. catenaria and D. dictyoides were also frequently isolated. A wide range of genotypes within the host species L. perenne, L. multiflorum, Festuca arundinacea and F. pratensis, and structural hybrids between F. arundinacea and L. multiflorum, were all equally susceptible to conidial infection by D. siccans in the glasshouse and showed similar development of leaf spot symptoms, even though Festuca spp. are not normally attacked in the field. However, when exposed to infection out of doors there was significant variation in resistance, both between species and often also between genotypes within the same species. As in so many other instances of fungal infection, tetraploidy appeared to confer a higher level of resistance. The degree of resistance of a F. arundinacea × L. multiflorum amphiploid and two succeeding backcross generations to L. multiflorum approximated to that of the more susceptible L. multiflorum parent. By contrast to D. siccans, when plants were inoculated with D. catenaria in the glasshouse, both intervarietal and intravarietal variation in leaf spot development was evident. Resistance to D. siccans appears to depend partly on a limitation of conidial production, and to D. catenaria on restriction of hyphal growth following infection, which may explain the relative discrepancies between field and glasshouse results. The implications for resistance breeding are discussed.

Electrophoretic characterization of six selected enzymes of peanut cultivars

The isozyme patterns (both anodic and cathodic) of esterase, catalase, leucine aminopeptidase, acid phosphatase, alcohol dehydrogenase and INT oxidase in individual seeds from several peanut cultivars ( Arachis hypogaea) were characterized by polyacrylamide and starch gel electrophoresis in relation to the stages of seed development, maturity, and germination, geographic areas where grown and phylogenetic relationship. Of the six enzymes examined, only esterase contained cathodic isozymes, of which the patterns served to distinguish between the Spanish and the Virginia-type peanuts. Anodic esterase and acid phosphatase zymograms of early developing and germinating peanuts could be distinguished from those of predormant and mature seeds and the latter showed much intravarietal variation which was consistent among cultivars and the geographic areas where grown. Anodic isozymes of catalase, leucine aminopeptidase, alcohol dehydrogenase and INT oxidase were synthesized very early in peanut development and remained constant through maturity and to at least 24 hr germination; they were consistent within and between peanut cultivars and they were not influenced by the environmental conditions of the areas where the peanuts were grown. The consistency of the isozyme patterns within and between cultivars supports the suggestion that plant breeding programs used to develop superior cultivars have produced genetic uniformity in peanuts.

Intra-varietal variation of yield in two varieties ofLolium perenne L.

Clones derived from the S. 321 and S. 24 varieties ofLolium perenne were grown as spaced plants with two fertilizer treatments and cut five times during one growing season. Considerable intra-varietal variation in yield occurred in both varieties, although the variance attributable to it was less than variances attributable to the cutting and fertilizer treatments. Linear regressions of the yields of individual clones on the mean yield of all the clones accounted for most of the variance attributable to the interactions of the clones with the cutting and fertilizer treatments. In both varieties the regression lines tended to pass through a common point. Greater intra-varietal variation was found in S. 24 than in S. 321, and this was reflected in the degree to which the regression lines actually passed through a common point. These results are discussed in relation to selection.

Intra-varietal variation. In lolium perenne

The intra-varietal variation of plants of Irish and S. 23 perennial ryegrass (Lolium perenne) growing in nutrient solution was studied in separate experiments.