SHORT-TIME SCALE DEVELOPMENT OF A GYMNODINIUM CATENATUM POPULATION IN THE RIA DE VIGO (NW SPAIN)1

Wind direction and fresh water runoff determine the circulation pattern of the Ría de Vigo (NW Spain), which in turn influence the selection and distribution of its phytoplankton populations. Coastal winds with a south–southwesterly component reverse the positive estuarine circulation in the Ría, causing an off-shore to in-shore flow of surface waters and, consequently, the outflow of inner waters via deeper layers. We found that this reversal imposed a selective force on the phytoplankton population: diatoms, which could not counteract the sinking movement of the surface waters, were diminished, while dinoflagellates remained in the water column. From the end of September to the beginning of October 1993, an accumulation of Gymnodimium catenatum Graham was observed coinciding with an intrusion of coastal water induced by westerly winds which provoked a reversal in the circulation of the Ría. The slow reestablishment of the positive estuarine circulation pattern, which was due to a weak coastal upwelling and considerable fresh water runoff, allowed the population of G. catenatum to flourish.     

NADH dehydrogenase: a new molecular marker for homoeology group 4 in Triticeae. A map of the 4RS chromosome arm in rye

Summary Structural gene loci encoding the monomeric isozymes nicotin adenin dinucleotide dehydrogenase (NADH dehydrogenase or NDH) have been located on the 4AL, 4B, and 4DS chromosome arms of Triticum aestivum cv Chinese Spring, on the 4RS chromosome arm of Secale cereale cultivars Imperial, King II, Dakold, and Ailes, on the 4S¹ S/7S¹ chromosome of Aegilops longissima, the 4E of Elytrigia elongata, and the CSU-A of Aegilops umbellulata. All the results support the homoeologous relationships among these chromosomes in the five species studied. In addition, a map of the 4RS chromosome arm in cv Ailes has been realized, linking loci Pgm-1 (located on the 4RS chromosome arm) and Ndh-1 (17.91 cM), with an estimated distance between both loci and the centromere of 20.00 cM and 32.12 cM, respectively.     

Daily rhythm of aggregation in the haematophagous bug Triatoma infestans (Heteroptera: Reduviidae)

Triatomine bugs show a temporal modulation of many activities. Here, we analyse the daily modulation of the aggregation behaviour of Triatoma infestans larvae and its chronobiological basis. In the laboratory, groups of six bugs were released over an experimental arena during six consecutive days, where their aggregation behaviour was quantified every hour. When submitted to a 12/12 h photoperiod (L/D), the larvae of T. infestans exhibited a cyclic pattern of aggregation with a 24 h period, evincing the existence of a daily rhythm of aggregation in this species. Bugs exhibited the maximum aggregation tendency at the end of the scotophase (7:00 h), moment in which they naturally search for refuges. The minimum aggregation (i.e. maximal dispersion) was observed during the last part of the photophase and beginning of the scotophase (15:00 to 1:00 h). This cyclic pattern disappeared when constant conditions of illumination (L/L) or darkness (D/D) were imposed to the bugs, suggesting the absence of an endogenous circadian control of this behaviour. Insects submitted to L/L and D/D photoperiods presented lower global levels of aggregation than those submitted to L/D conditions. The lack of an endogenous control and the relevance of light cycles as a synchronization signal are discussed as the temporal modulation of this behaviour might play an important role in the nocturnal habits of this species.     

Preparation and Solid-State Characterization of Inclusion Complexes Formed Between Miconazole and Methyl-β-Cyclodextrin

The aim of this study is to confirm the formation of inclusion complexes between miconazole (MCZ) and two derivatives of beta-cyclodextrin, methyl-beta-cyclodextrin (MβCD) and 2-hydroxypropyl-beta-cyclodextrin (HPβCD) in aqueous solution by phase solubility studies. Inclusion complexes with MβCD in the solid state were then prepared by different methods, i.e., kneading, coevaporation (COE), spray-drying (SD), and lyophilization (LPh). The physicochemical properties of these complexes were subsequently studied by means of differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques. Phase solubility diagrams with MβCD and HPβCD were classified as A_P type, indicating the formation of 1:1 and 1:2 stoichiometric inclusion complexes. The apparent stability constants (K_S) calculated from the phase solubility diagram were 145.69 M⁻¹ (K _1:1) and 11.11 M⁻¹ (K _1:2) for MβCD and 126.94 M⁻¹ (K _1:1) and 2.20 M⁻¹ (K _1:2) for HPβCD. The method of preparation of the inclusion complexes in the solid state was shown to greatly affect the properties of the formed complex. Hence, the LPh, SD, and COE methods produce true inclusion complexes between MCZ and MβCD. In contrast, crystalline drug was still clearly detectable in the kneaded (KN) product.     

Rapid identification of Triticeae genotypes from single seeds using the polymerase chain reaction

An easy and quick protocol has been developed for DNA analysis via PCR. Single cereal endosperm or small leaf pieces can be separately processed in several PCR reactions. The resultant PCR patterns are equivalents to those obtained with standard DNA extraction protocols using either specific or random primers. Intra-and inter-specific variability can be detected. This method allows the analysis of a large number of individuals in early stages prior to the plant sowing.     

On the consequences of aluminium stress in rye: repression of two mitochondrial malate dehydrogenase mRNAs

Plants have developed several external and internal aluminium (Al) tolerance mechanisms. The external mechanism best characterised is the exudation of organic acids induced by Al. Rye (Secale cereale L.), one of the most Al‐tolerant cereal crops, secretes both citrate and malate from its roots in response to Al. However, the role of malate dehydrogenase (MDH) genes in Al‐induced stress has not been studied in rye. We have isolated the ScMDH1 and ScMDH2 genes, encoding two different mitochondrial MDH isozymes, in three Al‐tolerant rye cultivars (Ailés, Imperial and Petkus) and one sensitive inbred rye line (Riodeva). These genes, which have seven exons and six introns, were located on the 1R (ScMDH1) and 3RL (ScMDH2) chromosomes. Exon 1 of ScMDH1 and exon 7 of ScMDH2 were the most variable among the different ryes. The hypothetical proteins encoded by these genes were classified as putative mitochondrial MDH isoforms. The phylogenetic relationships obtained using both cDNA and protein sequences indicated that the ScMDH1 and ScMDH2 proteins are orthologous to mitochondrial MDH1 and MDH2 proteins of different Poaceae species. The expression studies of the ScMDH1 and ScMDH2 genes indicate that it is more intense in roots than in leaves. Moreover, the amount of their corresponding mRNAs in roots from plants treated and not treated with Al was higher in the tolerant cultivar Petkus than in the sensitive inbred line Riodeva. In addition, ScMDH1 and ScMDH2 mRNA levels decreased in response to Al stress (repressive behaviour) in the roots of both the tolerant Petkus and the sensitive line Riodeva.     

Association of Isozymes with a Reciprocal Translocation in Cultivated Rye (SECALE CEREALE L.)

In rye (Secale cereale L. cv. "Ailés") the progeny of a cross between a structural heterozygote for a reciprocal translocation (involving the 1R chromosome) and a homozygote for the standard chromosome arrangement were analyzed for the electrophoretic patterns of eight different leaf isozymes and also for their meiotic configuration at metaphase I.——The Got-3 and Mdh-2b loci are linked to each other and also to the reciprocal translocation. The Mdh-2b locus is located in the interstitial segment of the 3Rq chromosome arm, with an estimated distance of 8 cM to the breakpoint. Therefore, the reciprocal translocation involves the 1R and 3R chromosomes.——Also, the Mdh-1 and 6-Pgd-2 loci are linked (16 ± 3 cM) and have been located on the 2Rq arm. Finally, the Per-3 and Per-4 loci are located on the 2Rp chromosome arm at an estimated distance of 26 ± 4 cM.     

Pollen germination and tube growth in rye (Secade cereale L.) homozygous and heterozygous for reciprocal translocations

Summary To contribute to the knowledge of the role of reciprocal translocations in rye, a component of fertility was estimated by comparing germination and pollen tube growth in homozygous and heterozygous plants for reciprocal translocations. The results obtained indicate that there are no differences in germination and pollen tube growth rate when homozygous and heterozygous plants as a whole are compared. However, there are significant differences in pollen tube growth between plants carrying different translocations. This suggests that the chromosome constitution of a plant is relevant to these fitness-estimating parameters together with its particular genetic background.     

Genetics of rye phosphatases: evidence of a duplication

Summary Genetic analyses were conducted on alkaline phosphatases of the endosperm of dry kernels and leaf acid phosphatases in four open pollinated and one inbred line of cultivated rye (Secale cereale L.). A total of seven alkaline phosphatase isozymes were observed occurring at variable frequencies in the different cultivars analyzed. We propose that at least five loci control the alkaline phosphatases of rye endosperm — Alph-1, Alph-2, Alph-3, Alph-4 and Alph-5 — all of which have monomeric behaviour. The leaf acid phosphatases are controlled by one locus and have a dimeric quaternary structure. All loci coding for alkaline phosphatase isozymes showed one active, dominant allele and one null, recessive allele, except for the locus Alph-3 which showed two active, dominant alleles and one null, recessive one. The linkage analyses suggest the existence of two linkage groups for alkaline phosphatases: one of them would contain Alph-2, Alph-4, Alph-5 and the locus/loci coding isozymes 6 and 7. This linkage group is located in the 7RS chromosome arm. The other group would include Alph-1 and Alph-3 loci, being located in the 1RL chromosome arm. Leaf acid phosphatases have been previously located in the 7RL chromosome arm. Our data also support an independent relationship between loci controlling the endosperm alkaline phosphatases and leaf acid phosphatases.