Morphological differences among Raphanus raphanistrum populations and their relationship to related crops

Wild radish (Raphanus raphanistrum) has developed introgressed populations after hybridization with its cultivated counterpart (R. sativus) in California. Hybridization with various Brassica and Sinapis species is also possible. To determine if hybridization is responsible of the genetic diversity of European populations, six wild radish populations with distinct morphological traits were sampled from geographically distant regions in Europe. Plants were cultivated in an oilseed rape field and in insect‐proof cages. Silique and flower morphology, growth, and reproductive traits were measured. The wild radish populations could be discriminated by the morphological traits, but not related to geographic regions. In particular, populations of one region showed wide variability in terms of silique shape and growth behaviour, and small‐sized flowers. Although the origin of morphological diversity in wild radish is unclear, i.e. native or due to gene flow from the cultivated radish or other Brassicaceae, significant morphological divergence was found that could have relevant effects on plant ecology and adaptation.     

Influence of larval and juvenile life history on age at first maturity in two tropical amphidromous fish species

This study investigates how age at first maturity of two tropical amphidromous species Sicyopterus lagocephalus (Pallas, 1770) and Cotylopus acutipinnis (Guichenot, 1863) varies in relation to their larval and juvenile life history. Reproductive stage was estimated based on histological observation of ovaries of more than 200 females of each species caught monthly over 1 year. The age of fish was estimated by interpreting the daily increments deposited on otoliths during the oceanic larval phase, and the juvenile phase in the river. The age at first maturity was approximately 9 months for S. lagocephalus and 7 months for C. acutipinnis, corresponding to approximately 70–130 and 90–130 days after they returned to freshwater respectively. For both species, the time spent in freshwater before maturity was significantly influenced by the duration of the pelagic larval stage at sea (PLD) and the season of return in freshwater. Individuals with a long PLD, or returning in freshwater during the warmer season, maturated faster once in freshwater. This reproductive advantage may minimise the risk of extirpation due to catastrophic events at each generation and thus probably benefits amphidromous species living in very unpredictable tropical rivers.     

Tree regeneration and plant species diversity responses to vegetation control following a major windthrow in mixed broadleaved stands

By increasing resource availability, canopy opening enhances tree recruitment as well as the development of neighbouring vegetation. The proliferation of early successional and highly competitive vegetation may have dramatic consequences on seedling establishment. However, differences in competitive abilities have been shown among the plant growth forms commonly encountered in forests. We may thus expect that vegetation management leading to control of different plant growth forms would have different consequences on tree seedling growth and development. To test this hypothesis, we analysed the effects of an intensity gradient of four vegetation control treatments (untreated, coppice control, coppice and non-tree plant control, and coppice, non-tree and pioneer (tree) plant control) on plant species richness and natural tree regeneration in three post-storm sites. Higher plant species richness and a better natural tree regeneration were observed in the more intensive treatments that significantly improved the balance of the relative abundance of tree species. Suppressing the more competitive vegetation, mainly Rubus fruticosus and graminoids, led to the recruitment and growth of tree species sensitive to competition and good tree species diversity. Practical recommendations in terms of vegetation control relative to tree regeneration and plant species richness are given.     

Inheritance of sethoxydim resistance in foxtail millet, Setaria italica (L.) Beauv.

Interspecific hybridization between foxtail millet cultivars (Setaria italica) and a green foxtail (S. viridis) resistant to the herbicide sethoxydim were undertaken to breed foxtail millet for improved herbicide resistance. Parents, reciprocal F₁ hybrids, F₂ selfed derived populations and BC₁ backcross progeny were produced and analysed for mortality and fresh weight over a range of dosages. All resistant progeny were 700 times more resistant than susceptible cultivars and was symptom free under current field dosages. Segregations of resistant and susceptible progeny (3:1 in F₂ and 1:1 in BC₁) were not dependent upon dosage. Heterozygous individuals displayed the same magnitude of resistance as homozygous plants at twelve times the recommended field dosage. Results suggested that sethoxydim resistance in foxtail millet was controlled by a single, completely dominant, nuclear gene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

Escape of transgenes from genetically modified oilseed rape, Brassica napus, into wild radish, Raphanus raphanistrum, depends on sexual compatibility. The variation in prezygotic barriers of two different cultivars for interspecific hybridization with a population of wild radish was investigated by hand crossing and fluorescence microscopy of pistils. Significant differences were observed between oil seed rape cultivars in their ability to accept wild radish pollen germinating onto their stigma and the rate of fertilization of ovules. Some differences among the pollen donor plants were also detected. These results suggest that the rate of interspecific hybridization in the field would depend upon the oilseed rape cultivar and the genotype composition of the local wild populations. The implication of S-related genes, as revealed through identification by pistil tissue prints of class I and II S-types of SLG (S-Locus Glycoprotein) and SLR1 (S-Locus Related),and immuno-IEF, was not significant. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inheritance and relationships of important agronomic traits in almond

The inheritance of 16 important agronomic traits and its relationship were studied for four years in a population of 167 almond [P. dulcis (Mill.) D.A. Webb] seedlings obtained from a cross between the French selection ‘R1000’ (‘Tardy Nonpareil’ × ‘Tuono’) and the Spanish cultivar ‘Desmayo Largueta’. For some traits (blooming and leafing date) descendants segregated between the value of both progenitors, meanwhile for others the mean of the offspring was lower (bloom density, productivity and ripening date) or higher (in-shell/kernel ratio and double kernels). As expected, kernel bitterness and self-incompatibility behaved as monogenic traits. Some important correlations between traits were detected. The implications of the transmission and the correlation of these traits in the breeding programmes are discussed.     

Potential for Selection in the Progeny of an Interspecific Hybrid in Foxtail Millet

Genetic variation for morphology and grain yield components was studied in the F₂ and 14 F₃ families of an interspecific cross of Setaria italica (foxtail millet) with S. viridis s. s. (green foxtail). It appeared possible to recover the cultivated type using a simple selection procedure in F₂ and F₃. Comparison with a cross involving S. viridis var. major (giant green foxtail) is discussed.     

Phosphorus content in five representative landscape units of the Lomas de Arequipa (Atacama Desert-Peru)

Phosphorus forms and content were studied in soils of the Lomas de Arequipa (Atacama desert, Peru) using a fractionation method. These Lomas are small hills periodically submitted to the El Niño-Southern Oscillation (ENSO) which causes heavy rainfall. Sample soils were randomly selected in five landscape types characterized by vegetation: cactaceae (Cac), cactaceae and herbaceous (CacHerb), shrubs (Shr), trees with cover < 60% (Tree) and shrubs or trees with cover > 60%) (ShrTree). All the soils were strongly acidic and classified as loamy sand, sandy loam or silt loam. Organic carbon content was under 1% in Cac or CacHerb, then increased strongly in ShrTree (6.50%). Considering phosphorus, all the forms (labile as well resistant forms) increased markedly from Cac soils to ShrTree soils. In all the soils, the labile forms (Resin-P: range 45–105 μg g^− 1; NaHCO3-Pi: 23–123 μg g^− 1; or NaHCO3-Po: 10–122 μg g^− 1) were very high. These high phosphorus contents were attributed to the specific climatic conditions of the Lomas that feature a long period of vegetation dormancy (very dry period) and a short period of growth, following ENSO-associated precipitation. We suggested that during the dry period, plant decay and microbial cells death lead to release and accumulation of labile P in the soil, the rainfall wetting the soil, permitting vegetation growth. In this respect, the Lomas climatic conditions contribute to soil fertility, especially as labile forms of phosphorus are chiefly concerned.     

Quantification of 4-methylimidazole in class III and IV caramel colors: validation of a new method based on heart-cutting two-dimensional liquid chromatography (LC-LC)

4-Methylimidazole (4MeI) is a nitrogen compound formed during the manufacture of class III and IV caramel colors. The European Commission has limited its content to 250 ppm. Two methods were compared to perform 4MeI quantification in caramels. The first one, currently used and considered to be the reference method, consists of a hot extraction of caramel color with dichloromethane and an analysis of the acetyl derivative of the extract by gas chromatography coupled to mass spectrometry (GC-MS). The second method is based on the heart-cutting two-dimensional liquid chromatography technique (LC-LC) to directly separate 4MeI from the other components present in caramel color sample (diluted in water) in <30 min. The accuracy profile validation method and the comparison between the results obtained with the two methods show that the new and completely automated LC-LC method is usable to quantify 4MeI in caramels.