Genetic diversity in the orange subfamily Aurantioideae. I. Intraspecies and intragenus genetic variability

Despite the great economic importance of citrus, its phylogeny and taxonomy remain a matter of controversy. Moreover pathogens of increased virulence and dramatic environmental changes are currently spreading or emerging. The objectives of the present paper, measuring genetic variability and studying its pattern of distribution, are crucial steps to optimize sampling strategies in the search of genotypes that tolerate or resist these threatening factors within the huge array of Citrus and Citrus related species. Their intraspecific and intrageneric variability was studied comparatively by means of ten enzymatic systems using eight different measures. The analysis of ten enzymatic systems allowed us to distinguish all the species and all but one artificial hybrid. The species with the lowest genotypic variability are C. myrtifolia, C. deliciosa (willow leaf mandarin), C. paradisi (grapefruit), C. limon (lemon) and C. sinensis (sweet orange), while Severinia buxifolia shows the highest value. A broad spectrum of heterozygosity values was found in the collection. Lemons (C. limon, C. meyeri, C. karna, C. volkameriana), limes (C. aurantifolia, C. limettioides, C. lattifolia) and C. bergamia show a very high percentage of heterozygosity which indicates an origin through interspecific hybridization. Two main factors limit genetic intraspecific variability: apomictic reproduction, where nucellar embryos are much more vigorous than the zygotic ones, and nurserymen selecting against variability in the seedling stage of the rootstocks or in propagating the scion cultivars vegetatively. Additionally, self-pollination appears in some species mainly used as rootstocks which would explain their low heterozygosity values. Genetic differences between species and genera are in general high, which suggests that adaptation might have played an important role during the evolution of the orange subfamily.     

Salt tolerance in Lycopersicon species VI. Genotype-by-salinity interaction in quantitative trait loci detection: constitutive and response QTLs

 A study of genotype-by-salinity interaction was carried out to compare the behavior of quantitative trait loci (QTLs) in two F₂ populations derived from crosses between the cherry tomato, Lycopersicon esculentum Mill. var. cerasiforme, and two wild relatives Lycopersicon pimpinellifolium (Jusl.) Mill. and Lycopersicon chesmannii f. minor (Hook. f.) Mull., grown at two environmental conditions (optimum and high salinity). QTLs for earliness and fruit yield could be classified into four groups: “response-sensitive”, those detected only under control conditions or whose contribution significantly decreased in salinity; “response-tolerant”, detected only in salinity or in which the direction of their additive effects changed; “constitutive”, detected in both growing conditions; and “altered” QTLs, those where the degree of dominance changed according to the presence or absence of salt. Epistatic interactions were also influenced by the salt treatment. This differential allele effect at some (non-constitutive) QTLs induced by salt stress will make selection under an “optimum environment” unfruitful for the “response-tolerant” QTLs. Similarly, selection under salinity will ignore “response-sensitive” QTLs. Given that salinity is highly variable in the field, marker-assisted selection should take into account not only the “response-tolerant” but also the “response-sensitive” QTLs although there might be cases where selection in some QTLs for both conditions is not feasible. Comparing both populations, very few QTLs showed the same behavior. Received: 5 August 1996 / Accepted: 25 October 1996     

Salt tolerance in Lycopersicon species. V. Does genetic variability at quantitative trait loci affect their analysis?

 Salt tolerance was studied comparatively in three families derived from crosses between Lycopersicon esculentum Mill. and two related wild species [two accessions of Lycopersicon pimpinellifolium (Jusl.) Mill. and one accession of Lycopersicon chesmannii f.minor (Hook.f.) Mull.] by means of QTL analysis of fruit yield and earliness under conditions of salinity. From six polymorphic genomic regions involved in salt tolerance, three contained segregant salt-tolerant QTLs for the three families; two were found only in both families derived from L.pimpinellifolium; and one, involved in fruit number, was detected only in one of the L.pimpinellifolium families. Some differences regarding the effects of the wild alleles at orthologous QTLs were found. These effects were always negative in the L. chesmannii family. Comparing both L. pimpinellifolium families, the “wild” alleles at two out of nine common QTLs for fruit number and weight had effects with opposite directions, and the mode of gene action was clearly different at five of them. QTL analysis of earliness revealed the largest genotypic differences among families. Most drastic differences were found for the epistatic interactions in which all genomic regions containing QTLs were involved. These interactions between unlinked genes increased the range of variation of means, mainly upwards, as compared with genotypes at individual QTLs. Only one (affecting fruit weight) out of 27 interactions was detected in both L.pimpinellifolium families. Heterotic effects found for salt tolerance in one of the families can be explained by the presence of overdominant (or pseudo-overdominant) and dominant gene effects at QTLs controlling final fruit yield under conditions of salinity. Allelic variation at salt-tolerant QTLs exists, changing the additive and, mainly, the non-additive components of the genotypic value. Consequently, it may negatively affect the general applicability (or efficiency) of marker-assisted selection to improve salt tolerance in other segregant populations where QTLs were not studied. The use of more informative co-dominant markers, like microsatelites, might overcome these problems. Received: 5 August 1996/Accepted: 25 October 1996     

Carbamoyl phosphate synthetase, ornithine transcarbamylase, and aspartate transcarbamylase activities in the pea ovary : changes with senescence of the unpollinated ovary or with fruit set induced by gibberellic Acid

Carbamoyl phosphate synthetase (CPS), ornithine transcarbamylase (OTC), and aspartate transcarbamylase (ATC) were assayed in extracts from unpollinated ovaries of Pisum sativum L. CPS and OTC activities were, per milligram protein, the highest reported in a plant tissue, representing an estimated 0.1% of the protein in the ovary. The OTC/CPS and ATC/CPS ratios were about 100 and 0.5, respectively, indicating that most of the carbamoyl phosphate is used for arginine synthesis. The weight, protein content, and CPS, OTC, and ATC activities per ovary were determined during the senescence of the ovary and also during fruit set induced by treatment with gibberellic acid (GA₃). In the nontreated ovary the weight and the protein first increased and then decreased dramatically, but the decrease in protein took place much earlier. In the GA₃-treated ovaries the increase in weight was considerably greater than the increase in the protein. Whether or not the ovaries were treated with GA₃, CPS, OTC, and ATC activities closely followed the changes in protein, and thus their ratios and specific activities remained essentially constant. It appears that treatment with GA₃ increases the amount of protein and enzymic activities by preventing a large increase in the rate of protein degradation. In addition, the effects of acetylglutamate, ornithine, and UMP on CPS activity were studied. The pea enzyme exhibits regulatory properties intermediate between those of Escherichia coli and the ureotelic liver enzymes.     

Participation of the renin-angiotensin system in experimental renovascular hypertension

Hypertension was induced in Wistar rat by means of a clip in the left renal artery. After two weeks (acute stage) and sixteen weeks (chronic stage) the animals had a significant increase in arterial pressure (AP) and plasma renin activity (PRA). At both stages, nephrectomy or revascularization of the ischemic kidney returned AP and PRA to the normal level, both in the short term (1 day) and long term (60 days).     

Chemical and immunological properties of galactomannans obtained from Histoplasma duboisii,Histoplasma capsulatum,Paracoccidioides brasiliensis and Blasomyces dermatitidis

Serologically active polysaccharide, galactomannan, was isolated from whole cells ofH. capsulatum, H. duboisii, P. brasiliensis andB. dermatitidis, and their chemical structure and immunological properties were described.     

Kinetic and Morphological Observations on the Yeast Phase of Histoplasma capsulatum During Protoplast Formation

Protoplast formation by Histoplasma capsulatum yeasts using high concentrations of MgSO(4) occurs either by lysis of the bud or lysis of the entire cell wall. Both mechanisms may also occur simultaneously. Neither the protoplast emerging through a hole in the cell wall nor the freshly released protoplast has a recognizable cell wall or the remnant of such. The protoplast contains all the organelles of the normal cell except for mesosomes. During protoplast formation the nucleus increases in size and produces several nuclear masses by the invaginations of the internal layer of the nuclear membrane. All these nuclear masses are surrounded by the external layer of the nuclear membrane. Several nuclei with a normal nuclear membrane are formed later.     

Baculovirus interaction with nontarget organisms: a virus-borne reporter gene is not expressed in two mammalian cell lines

The safety of baculoviruses with respect to mammalian species was studied by using a genetically engineered recombinant of Autographa californica nuclear polyhedrosis virus. This recombinant contains the chloramphenicol acetyltransferase (CAT) gene under the control of a mammalian-active promoter and expresses substantial levels of CAT activity on infection of permissive and nonpermissive insect cells (L.F. Carbonell, M.J. Klowden, and L.K. Miller, J. Virol. 56:153-160, 1985). Extremely low levels of CAT activity were detected in mouse and human cell lines that were continuously exposed to the A. californica nuclear polyhedrosis virus recombinant. The appearance of CAT was not inhibited by cycloheximide. Isopycnic centrifugation of purified inoculum showed that a low level of CAT activity was associated with the insect-derived viral particles. Thus, the observed CAT activity is carried into the cells with the virus inoculum, and active expression of the baculovirus-borne CAT gene is not observed in either cell line. The inability of the CAT gene to be expressed in these cell lines with this model system provides additional assurance of the safety of insect baculoviruses with respect to mammalian species.     

Treatment results of nine patients with Burkitt's lymphoma

From 6/79 until 2/86, 9 patients (median age 39) with Burkitt's lymphoma were treated. Stage D disease was seen in 7 cases, stage C in two and stage A in one. The main symptom was abdominal pain or a rapidly progressing abdominal tumor. Three patients had bone marrow involvement and two had a Burkitt's leukemia. Three had typical chromosomal aberrations. Therapy consisted of a variety of chemotherapy regimens plus additional radiotherapy and/or bulk surgery. Two patients achieved complete remissions (of 6 and 20+ months duration), and 4 partial remissions were obtained. The remaining patients had either progressive, drug resistant disease or died early. One patient is currently alive and in complete remission at 20+ months. A second patient is alive at 20+ months in partial remission with traces of IgM-paraprotein still detectable. The main causes of death were tumor-lysis syndrome (4 patients) and therapy related sepsis with progressive tumor (3 patients). This poor outcome is probably due to a high proportion of high-risk patients and suboptimal therapy for this rapidly proliferating tumor.