Measurement of motive force for cytoplasmic streaming in characean internodes

Summary With an attempt to measure the motive force responsible for cytoplasmic streaming in characean internodal cells, the difference between densities of cytoplasm and vacuolar sap was heightened by about 10 times (density of vacuolar sap was made larger than that of cytoplasm) by replacing the natural vacuolar sap ofChara corallina with an artificial one of higher density. Endoplasmic flow contiguous to the peripheral actin cables (peripheral flow of endoplasm) in the centrifugal direction was not influenced at all by the application of centrifugal acceleration up to 1400 g. We thus concluded that the motive force for the peripheral flow should be much larger than 12dyn/cm², a figure more than 10 times larger than that for bulk endop lasmic flow so far reported.Dedicated to Emeritus Professor Noburo Kamiya on the occasion of his 80th birthday     

Dedifferentiation and microtubule reorganization in the apical cell protoplast ofSphacelaria (Phaeophyceae)

Summary The apical cell ofSphacelaria, a tip-growing filamentous brown alga, and its protoplast constitute a model for the investigation of the consequences of cell wall removal on microtubular cytoskeletal organization and cell polarity. In the apical cell, the microtubular cytoskeleton is strongly polarized and, in most cases, extends from two centrosomes to the cortex where it constitutes a fine meshwork. Observations of microtubule dynamics throughout the cell cycle emphasize the coincidence between orientation of the mitotic axis and cell polarity. Just after protoplast isolation, dramatic alterations of initial polarity are observed, whatever the mitotic stage. In particular, the coincidence between cytoplasmic polarity and polarity of the system nucleus-centrosomes is lost in most cases. 12–24 h after protoplast isolation, the cell shows a more symmetrical organization while a dense cortical microtubular network spreads out concomitantly with wall reformation. Our discussion emphasizes the possible relationship between cell polarity and cell totipotency, and the relevance of such a model for higher plant studies.     

Craniometrical variations among eastern Brazilian marmosets and their systematic relationships

The craniometrical variations among marmosets on the eastern coast of Brazil or theCallithrix jacchus group (C. jacchus, C. penicillata, C. kuhli, C. geoffroyi, C. flaviceps, andC. aurita) were analyzed to test various hypotheses for the arrangement of the species and phylogenetic relationships ofC. kuhli andC. flaviceps. Q-mode correlation coefficients and principal component analysis were employed to extract important shape factors from the craniometrical data. On this basis, the shape distances among the eastern Brazilian marmosets were found to be larger than those between the marmosets which are recognized as distinct species. This evidence supports the hypothesis that the members of theC. jacchus group are distinct species.C. kuhli shows the strongest resemblance toC. geoffroyi within theC. jacchus group.C. flaviceps is the most similar toC. aurita in its cranial shape. These findings indicate thatC. kuhli is most closely related toC. geoffroyi, whileC. flaviceps is toC. aurita.     

Chloroplast DNA phylogeny of Lens (Leguminosae): origin and diversity of the cultivated lentil

A restriction-site analysis of chloroplast DNA (cpDNA) variation in Lens was conducted to: (1) assess the levels of variation in Lens culinaris ssp. culinaris (the domesticated lentil), (2) identify the wild progenitor of the domesticated lentil, and (3) construct a cpDNA phylogeny of the genus. We analyzed 399 restriction sites in 114 cultivated accessions and 11 wild accessions. All but three accessions of the cultivar had identical cpDNAs. Two accessions exhibited a single shared restriction-site loss, and a small insertion was observed in the cpDNA of a third accession. We detected 19 restriction-site mutations and two length mutations among accessions of the wild taxa. Three of the four accessions of L. culinaris ssp. orientalis were identical to the cultivars at every restriction site, clearly identifying ssp. orientalis as the progenitor of the cultivated lentil. Because of its limited cpDNA diversity, we conclude that either the cultivated lentil has passed through a genetic bottleneck during domestication and lost most of its cytoplasmic variability or else was domesticated from an ancestor that was naturally depauperate in cpDNA restriction-site variation. However, because we had access to only a small number of populations of the wild taxa, the levels of variation present in ssp. orientalis can only be estimated, and the extent of such a domestication bottleneck, if applicable, cannot be evaluated. The cpDNA-based phylogeny portrays Lens as quite distinct from its putative closest relative, Vicia montbretii. L. culinaris ssp. odemensis is the sister of L. nigricans; L. culinaris is therefore paraphyletic given the current taxonomic placement of ssp. odemensis. Lens nigricans ssp. nigricans is by far the most divergent taxon of the genus, exhibiting ten autapomorphic restriction-site mutations.     

Inheritance of resistance to blackmold (Alternaria alternata (Fr.) Keissler) in two interspecific crosses of tomato (Lycopersicon esculentum ×L. cheesmanii f.typicum)

Inheritance of resistance to blackmold, a disease of ripe tomato fruit caused byAlternaria alternata, was studied in two interspecific crosses. The parents, F₁ and F₂ generations of a cross between the susceptibleLycopersicon esculentum Mill. cultivar Hunt 100 and the resistantL. Cheesmanii f.typicum Riley accession LA 422, and the parents, F₁, F₂, F₃, and BC₁ P₂ generations of a cross between the susceptibleL. Esculentum cv. VF 145B-7879 and LA 422 were evaluated. The following disease evaluation traits were used: symptom rating (a symptom severity rating based on visual evaluation of lesions), diseased fruit (the number of diseased fruits divided by the total number of fruit scored), and lesion size (a function derived from the actual lesion diameter). Generation means analysis was used to determine gene action. The data of the Hunt 100 × LA 422 cross fit an additive-dominance model for all three traits. The VF 145B-7879 × LA 422 cross data best fit a model that included the additive × additive and additive × dominance interaction components for the trait diseased fruit, whereas higher-order epistatic models would have to be invoked to fit the data for the traits symptom rating and lesion size. A minimum of one gene segregated for all three traits. Broad-sense heritability estimates ranged from 0.09 to 0.16 for all three traits, indicating that selection for improved resistance to blackmold will require selection on a family performance basis.     

Quantitative analysis of the effect of selection history on sugar yield adaptation of sugarcane clones

An objective of the CSR sugarcane breeding programme in Australia was to assess the scope for broadening the genetic base of the commercial sugarcane germ plasm through interspecific hybridization with Saccharum spontaneum clones. The contribution of both selection history and S. spontaneum to sugar yield and its components was investigated in the germ plasm pool assembled. The analysis was conducted on a data-set of 256 clones, consisting of parents and full-sib families generated from 32 biparental crosses, tested in six environments. The minimum number of generations back to S. spontaneum ancestor in the clone's pedigree was used as a germ plasm score. The geographical origin and selection history of each parent and their use in the biparental crosses were used to develop a selection history score for parents and offspring. The variation for seven attributes, cane yield, commercial cane sugar %, sugar yield, stalk number per stool, stalk weight, fibre % and ash % juice was partitioned according to the germ plasm and selection history scores. Significant (P<0.05) clone variation and clone x environment interaction for all attributes was present. The germ plasm scores accounted for a significant (P<0.05) component of the clone variation for all of the attributes except cane yield. There was an increase in sugar yield with an increase in the minimum number of generations back to a S. spontaneum clone. The selection history groups accounted for a high proportion of the variation among parental clones for all of the attributes except cane yield. This suggested that parents were the outcome of strong selection pressure for the commercial cane attributes. However, the selection history groups for the offspring produced by random mating of parents did not account for a high proportion of the variation for the attributes. Using the mixture method of classification we partitioned the 256 clones into five groups for patterns of performance for the seven attributes across the six environments. The five groups emphasized major differences in the patterns of performance for the seven attributes across environments. The distribution of germ plasm and selection history scores in each of the five groups indicated that their patterns of performance were associated with selection history and minimum generations to S. spontaneum. Therefore, both the analysis on selection history and germ plasm scores (extrinsic classification) and the analysis on the mixture method of classification (intrinsic classification) emphasized the influence of selection history on the sugar yield of sugarcane.     

Ecogeographical distribution and differential adaptedness of multilocus allelic associations in Spanish Avena sativa L.

We determined the nine-locus isozyme genotype of 267 landrace accessions of Avena sativa from 31 provinces of Spain. Our results establish that level of genetic variability is usually high both within and among accessions of this heavily self-fertilizing hexaploid grass and that multilocus genetic structure differs in various ecogeographical regions of Spain. We concluded that selection favoring different multilocus genotypes in different environments was the main integrating force that shaped the internal genetic structure of local populations as well as the overall adaptive landscape of A. sativa in Spain. Implications in genetic resource conservation and utilization are discussed.     

Comparison of RAPD and RFLP genetic markers in determining genetic similarity among Brassica oleracea L. genotypes

Genetic similarity among 45 Brassica Oleracea genotypes was compared using two molecular markers, random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphisms (RFLPs). The genotypes included 37 broccolis (var. italica), five cauliflowers (var. botrytis) and three cabbages (var. capitata) which represented a wide range of commercially-available germplasm, and included open-pollinated cultivars, commercial hybrids, and inbred parents of hybrid cultivars. Fifty-six polymorphic RFLP bands and 181 polymorphic RAPD bands were generated using 15 random cDNA probes and 62 10-mer primers, respectively. The objectives were to compare RFLP and RAPD markers with regard to their (1) sampling variance, (2) rank correlations of genetic distance among sub-samples, and (3) inheritance. A bootstrap procedure was used to generate 200 random samples of size n (n=2,3,5,... 55) independently from the RAPD and RFLP data sets. The coefficient of variance (CV) was estimated for each sample. Pooled regressions of the coefficient of variance on bootstrap sample size indicated that the rate of decrease in CV with increasing sample size was the same for RFLPs and RAPDs. The rank correlation between the Nei-Li genetic similarity values for all pairs of genotypes (990) based on RFLP and RAPD data was 0.745. Differences were observed between the RFLP and RAPD dendrograms of the 45 genotypes. Overlap in the distributions of rank correlations between independent sub-samples from the RAPD data set, compared to correlations between RFLP and RAPD sub-samples, suggest that observed differences in estimation of genetic similarity between RAPDs and RFLPs is largely due to sampling error rather than due to DNA-based differences in how RAPDs and RFLPs reveal polymorphisms. A crossing algorithm was used to generate hypothetical banding patterns of hybrids based on the genotypes of the parents. The results of this study indicate that RAPDs provide a level of resolution equivalent to RFLPs for detemination of the genetic relationships among genotypes.     

First controlled progenies checked by isozymic markers in cultivated yams Dioscorea cayenensis-rotundata

As tested progeny have never been obtained, breeding studies on African yams (Dioscorea cayenensisrotundata) are scarce. We report here the first progenies checked by isoenzyme markers. This was made possible by the choice of well-known genitors [one male (cv Zrezrou) and three females (cvs Sopéré, Dahomey and C 20)] and special hybridization conditions. Six enzymatic systems [esterase (EST), isocitrate dehydrogenase (ICD), malate dehydrogenase (MDH), 6-phosphogluconate dehydrogenase (6PGD), shikimate dehydrogenase (SDH), and phosphoglucoisomerase (PGI)] were used to check the progenies and detect outbreeding. Despite the small number of progeny, it was possible to provide information on the genetics of the isoenzymatic systems.     

A population analysis of Robertsonian and Ag-NOR polymorphisms in brown trout (Salmo trutta)

An analysis of Robertsonian polymorphism and variation in the number of active NORs has been carried out in several populations of brown trout (Salmo trutta) from Northwestern Spain. The karyotype of this species appears to be soundly established, and essentially no variation has been found in chromosome number. Interindividual and interpopulation variation in arm number was detected, with figures ranging between 100 and 102 among individuals, and between 100.10 and 100.80 among populations. This variation in arm number is solely attributable to the polymorphism of the short arm of the main NOR-bearing pair 11, which can appear from acrocentric to metacentric in different individuals. Most populations analyzed showed the standard distribution of active NORs previously observed in this species. The Miño drainage basin, and specially the Chamoso population, showed a multi-chromosomal distribution of active NORs, with several new locations, always telomeric. In most cases no concordance was observed between previously detected rDNA sites in S. trutta and the new Ag-NOR locations. This fact suggests a transposition mechanism rather than an activation of silent rDNA sites to explain this multichromosomal NOR pattern.