Genetic identification of native populations of fluvial white-spotted charr <Emphasis Type="Italic">Salvelinus leucomaenis</Emphasis> in the upper Tone River drainage

ABSTRACT:   Stocking of exogenous, hatchery-reared white-spotted charr Salvelinus leucomaenis has been conducted throughout much of their range in Honshu Island, Japan, to increase angling opportunities. Although the native charr populations are thought to have declined because of hybridization with introduced fish, their distribution and genetic status have been uncertain. Fine population structures of charr in the upper Tone River drainage were examined using mitochondrial DNA and microsatellite analyses so as to clarify the presence of native populations. One common mtDNA haplotype was detected in all populations in the Ohashi River and Watarase River, and four and one tributary populations were monomorphic for such haplotypes, respectively. However, several haplotypes, considered to have originated from stocked hatchery fish, were observed in the stocked and the remaining populations. Judging from the genetic integrity over a fine geographic scale, the former were considered as indicative of native populations and the latter as admixtures with hatchery fish. Comparisons of genetic diversity, deviations from the Hardy–Weinberg equilibrium, principal component analysis, and relatedness estimations based on microsatellite DNA can also provide evidence for distinguishing native populations from those influenced by hatchery fish.     

Genetic diversity of natural populations of Atriplex halimus L. in Morocco: An isoenzyme-based overview

Based on polyacrylamide gel electrophoresis, nine natural populations of Atriplex halimus L., a perennial shrub, collected in different regions of Morocco, were studied for their genetic variation using isoenzyme polymorphism of the highly active enzyme systems: esterases (EST), acid phosphatases (ACP) and glutamate oxaloacetate transaminase (GOT). Different allozyme frequencies from 7 different loci were obtained for all populations of this halophyte species. High levels of genetic diversity were revealed. The mean number of alleles per locus (A = 1.9–2.0), the percentage of polymorphic loci (p = 71.4–85.7) and the mean expected heterozygosity (H_e = 0.339–0.385) showed an important variability in all populations. Gene diversity was essentially explained by the within population component. The between populations differentiation accounted for 8% of the whole diversity (F_ST, averaged over all loci, is 0.08). The relationships among the 9 populations were inferred from the Nei’s genetic distances. Four major groups were formed. The northern population ‘Tanger’, forming a unique group, was highly divergent from the other groups. It appeared that the genetic distance between all groups was related to the geographic distance that separates them. This revised version was published online in August 2006 with corrections to the Cover Date.     

Value of permanent grassland habitats as reservoirs of Festuca pratensis Huds. and Lolium multiflorum Lam. populations for breeding and conservation

European natural and semi-natural grassland form reservoirs of genetic resources containing highly adapted and variable ecotype populations of forage plants. Variation within these reservoirs is stimulated by variation in natural and anthropogenic site-related factors. Changes in agricultural practices lead to the loss of many characteristic habitats. In order to preserve resources for breeding, targeted conservation strategies for germplasm in gene banks (ex-situ) or on site (in-situ) are needed. In order to define site-related criteria for the potential of habitats to preserve valuable resources for breeding and conservation, 38 different habitats across Switzerland were selected to collect Festuca pratensis Huds. and Lolium multiflorum Lam. ecotype populations. Phenotypic variation and population differentiation of 60 single plants were evaluated in a field experiment using 16 morpho-physiological traits. For F. pratensis, ecotype populations and cultivars were clearly separated and there was a significant correlation between diversity of morphological traits and geographic location of sampling sites. For L. multiflorum no clear separation of ecotype populations and cultivars was observed suggesting gene flow from adjacent temporary leys into permanent grassland. Several ecotype populations were superior to cultivars in important traits such as early heading or resistance to winter damage, indicating the importance of natural habitats as a reservoir of genetic resources for breeding. In conclusion, maintenance of permanent grassland in contrasting environments appears to be a promising strategy for preserving valuable genetic variation of forage grasses. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetical Studies of Resistance of Powdery Mildew in Barley Lines Derived from Hordeum spontaneum Collected from Israel

Genetical studies on mildew resistance were carried out with Hordem spontaneum derived lines. A total of 28 lines (66 %) showed monofactorial segregation for mildew resistance, For 14 lines, a bifactorial mode of inheritance was found. In total fifty six mildew resistance genes take part in the inheritance of mildew resistance of the H. spontaneum derived lines, while the presence of known genes for mildew resistance (i.e, Ml-a.9 and Ml-p) was established only in two cases. Independent segregation from the Ml-a locus was found in 10 mbnofaetorial segregating lines, The genes conditioning mildew resistance in barley lines derived from the accessions 1B-54B, RS 170-47, RS 20-1. 1B-86B, RS 145-39 and 1B–152B of H. spontaneum were closely linked or alleles to the Ml-a locus, but shown to be different from 15 previously identified Ml-a alleles. It is suggested that these genes should be designated Ml-a16, Ml-18, Ml-19 Ml-20 and Ml-a21 respectively. No recombinants were found in test crosses when both parents carried genes/alleles of the Ml-a locus. In addition, polymorphism has been observed also for the Ml-a locus. In 4 lines mildew resistance was conditioned by two dominant complementary genes. For one of the 2 genes, conditioning mildew resistance of line RS 42-8 × OrioL a new locus was found located near the centromere of the long arm of chromosome 5, and should be designated Ml-i The potential use of H. spontaneum genes for mildew resistance in barley breeding is discussed.     

Morphological variation in Astragalus hamosus L. and Coronilla scorpioides L. populations of Tunisia

Morphological variation between Astragalus hamosus and Coronillascorpioides populations was studied using local germoplasm collected in northern and central Tunisia. Twenty-one morphological traits were recorded and data were analysed using complementary statistical analysis. Considerable variation based on morphological and agronomical traits was found between populations and for both species. Pod and peduncle lengths as well as flowers number were the most discriminant variables between populations. Differences were also found for variables like seed number per pod, seed yield and dry matter production. Significant correlations were found between plant traits and the environmental parameters of the origin sites. This study revealed enough variation among populations to initiate a selection programme for pasture improvement in arid and semi-arid areas of Tunisia, where the two species are well adapted. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection for seed yield in Middle American versus Andean × Middle American interracial common-bean populations

The objective of this study was to compare the seed yield, seed weight, and maturity of random lines derived from two contrasting populations of common bean ( Phaseolus vulgaris L.): Middle American (TR 7790) and Andean × Middle American (TR 7791). TR 7790 involved crosses between common-bean races of Middle American origin only (Mesoamerica and Durango), whereas TR 7791 involved crosses between races of Middle American and Andean origin (Mesoamerica and Nueva Granada). A total of 85 random lines from each of these two double-cross, interracial populations, a bulk sample of both populations, and all parents were evaluated in a replications-in-set design in eight environments in Colombia between 1991 and 1993. The mean yields of parents, population bulk, and lines from TR 7790 were significantly higher (P < 0.05) than those of TR 7791. Six lines in TR 7790 and nine lines in TR 7791 yielded significantly higher (P < 0.05) than the mean of their parents. Four lines from TR 7790 out-yielded the highest-yielding line from TR 7791. Moreover, while three lines from TR 7790 out-yielded its best parent, none of the lines from TR 7791 out-yielded its highest yielding parent. Thus, substantial yield gains should be expected from interracial populations within the Middle American group of common beans, whereas selection for higher seed yield from Andean × Middle American populations would seem problematic.     

Assessment of Transmission Ability of Barley Yellow Dwarf Virus-PAV Isolates by Different Populations of Rhopalosiphum padi and Sitobion avenae

Populations of two aphid species from different geographic regions of Morocco were tested for their ability to transmit five barley yellow dwarf virus-PAV (BYDV-PAV) type isolates using Clintland 64 oat as the test plant. Transmission efficiencies were determined for 10 sub-populations of Rhopalosiphum padi and 12 sub-populations of Sitobion avenae. After a short acquisition access period (AAP) of 4h, all populations transmitted the virus but with different efficiencies. R. padi (Rp-S) and S. avenae (Sa-S) collected in the Settat region were the most efficient vectors, with transmission rates of 38% and 27%, respectively. R. padi (Rp-C) collected at Chaouen and S. avenae (Sa-B) at Berkane, were poor transmitters with respective vectoring abilities of 20% and 16%. These four sub-populations were chosen to study the acquisition of BYDV-PAV and the retention of virus within aphids in more detail. The transmission after two AAPs of 4h and 48h were compared. Starved aphids given a 4h AAP had significantly higher transmission efficiencies than non-starved aphids. However, after a 48h AAP, no difference was observed in the transmission between starved and non-starved aphids. Intraspecific variability was also detected by means of serial transfers of individual aphids after the given AAP. Following the first day of serial transfers, no differences were observed in transmission efficiency and virus titers for sub-populations within each species acquiring the virus during 48h, but there was significant variation when the virus was acquired in 4h. The levels of PAV antigen retained by aphids fed on healthy plants declined rapidly during the first day after acquisition, but remained fairly constant during the next 5–7 days depending on the length of the AAP. Virus antigen could be detected by ELISA in Rp-S and Sa-S for up to 11 days of serial transfer, but it was shown that aphids could retain and transmit BYDV-PAV for at least 3 weeks.     

Soil microbial populations and activities as influenced by legume green fallow in a semiarid climate

Tilled fallow-wheat (Triticum aestivum L.) (F-W) is the most commonly used cropping system in the semiarid Canadian prairie. However, because frequent fallowing degrades soil, a partial fallow with annual legumes as green manure [i.e. ‘green fallow’ (GF)] has been proposed as a soil conserving and more bio-resource efficient alternative to bare fallow. We conducted a 6-year study to compare the influence of four GF-W, a F-W and a continuous W (Cont. W) system, on soil microbial communities, microbial biomass (MB) and activities in an Orthic Brown Chernozem, silt loam (Aridic Haploboroll) at Swift Current, Sask., Canada. The four GF legumes used were black lentil (Lens culinaris Medikus), Tangier flatpea (Lathyrus tingitanus L.), chickling vetch (Lathyrus sativus L.) and feedpea (Pisum sativum L.). They were grown to full bloom and then incorporated with a tandem disk. Analysis of soil taken from 0 to 10 cm depth after growing wheat in the sixth year of the experiment (i.e. 15 months after the most recent legume GF had been turned under) showed that most of the soil biochemical and microbiological attributes assessed were significantly improved (compared to F-W) by increasing cropping intensity (Cont. W), and even more by using the GF systems. The average improvement gained from the four GF legumes relative to F-W, was 385% for number of bacteria, 210% for filamentous fungi, 170% for MB-C, 191% for MB-N, 205% for cumulative C mineralization in 30 days at 21 °C, 202% for dehydrogenase, 171% for phosphatase, and 287% for arylsulfatase activity. The biologically active C and N, when expressed as ratios of MB-C or MB-N to total soil C or N, increased from 1.6 and 2.0% in F-W to 1.9 and 2.6% in Cont. W and to an average of 2.4 and 3.5% in GF-W. A sensitivity analysis (ratio of other treatment values to value for F-W) showed that Cont. W, and the GF-W systems even more, increased all major soil biological attributes tested. Among the GF systems, lentil-W consistently increased sensitivity the most, while Tangier flatpea-W usually increased it the least. The dynamic direct and indirect microbiological attributes were more sensitive indicators of changes in soil productivity than total organic C or N. The sensitivity of the attributes decreased in the sequence: Bacteria>Arylsulfatase>Filamentous fungi≈Cumulative C mineralization≈Dehydrogenase>MB-N>Phosphatase≈MB-C. Compared to the earlier published sensitivities of select physical and chemical attributes of soil quality to these same agronomic treatments, the microbiological attributes proved to be far more sensitive and more responsive to the beneficial influence of legume green fallowing in this semiarid loam.