The fragrance (fgr) gene in natural populations of wild rice (Oryza rufipogon Griff.)

The Asian cultivated rice, Oryza sativa L. (spp. indica or japonica), is assumed to have originated from one or both of the two wild Asian species, O. rufipogon Griff. and O. nivara Sharma and Shastry. They occur throughout the monsoon Asia and west Oceania. Fragrance is the most important trait among the domesticated characters of basmati and jasmine rice of Asia. The gene for fragrance in a scented rice shows the presence of a mutated portion (i.e., an eight base pair deletion in exon 7) that result in its loss of fragrance. In the present study, 229 wild rice O. rufipogon accessions were genotyped for this locus using a PCR assay. The wild rice species contained the mutated allele of the fgr gene at a low frequencies of 0.23. The surveyed populations were in Hardy–Weinberg equilibrium. This observation supports the hypothesis that the allele for fragrance was already present in the wild rice, and that this trait appeared in scented rice cultivars because of selection by the farmers of genotypes possessing this character during the process of domestication.     

Differences in the apportionment of molecular and morphological variation in North American strawberry and the consequences for genetic resource management

Variation for 24 morphological traits measured in a greenhouse environment and 36 randomly amplified polymorphic DNA (RAPD) markers was assessed among 318 wild octoploid strawberry (Fragariaspp.) genotypes from diverse habitats across the northern USA. RAPD marker frequencies and certain leaf and flower morphology traits (petiole color, leaf mass/area ratio, leaflet length and width, flower and receptacle diameter, petal width, flowers/inflorescence) were significantly different between the F. chiloensis-platypetala and F. virginiana-glauca species complexes. The proportion of variation accounted for by provenance effects was lower for the RAPD markers than for most morphological traits, especially in the F. virginiana-glauca species complex. Morphological traits of potential adaptive importance group the collection into provenances within each species-complex, and reflect the significant habitat and geographic differences across the region from which the germplasm was collected. Variation among populations within provenances was low for the molecular and most morphological traits, with a much larger amount of variability among plants within populations. Most of the variation for the presumably more selectively-neutral RAPD data was among plants within populations and populations within provenances rather than among the provenances that were recognized based on morphological traits, especially in the F. virginiana-glauca complex. Patterns of diversity for morphological traits must be considered, along with more selectively-neutral molecular characters such as RAPDs, to formulate effective sampling strategies and to properly estimate the quantity and apportionment of diversity within this germplasm.     

Influence of soluble phosphorus fertilizer on the interaction between a vesicular-arbuscular mycorrhizal fungus and Azospirillum brasilense in barley (Herdeum vulgare L.)

Summary Pot-culture studies were carried out to examine the response of barley (Hordeum vulgare L.) to inoculation with Azospirillum brasilense and Glomus versiforme, singly and/or in combination, under varying levels of nitrogenous [(¹⁵NH₄)₂SO₄] and soluble phosphatic (single superphosphate) fertilizers. The interaction between both the endophytes led to increased growth and nutrition of the barley plants. Roots from plants inoculated with Azospirillum brasilense and Glomus versiforme exhibited very low acetylene reduction activity. N₂ fixation in the plants increased with the increase in plant growth but the mycorrhiza alone gave a low level of N₂ fixation in the plants compared to combined inoculation with both the endophytes.     

Sucrose,cytokinin, and ethylene influence formation of in vitro bulblets in onion and leek

Summary In vitro maintenance of plant organs can enhance programs in plant breeding and germplasm resources. In bulbous plants, such as onion (Allium cepa L.) and leek (A. ampeloprasum L.) induction and storage of in vitro bulblets could enable long term maintenance of special genotypes. In vitro cultivated seedlings of onion and leek were induced to form bulblets by increase in sucrose concentration (30, 50, 150 g/1), and addition of benzyladenine (BA-0, 12.5 mg/1), or ethephon (0, 5, 20 days). The highest bulbing ratios were obtained within combinations of sucrose and ethephon treatments. BA caused not only bulb swelling but also an increase of multiple adventitious shoot formation. Increasing the sucrose concentration and treatment with ethephon are used to obtain bulblets for in vitro storage under conditions of slow growth.Abbreviations BA benzyladenine - BDS medium according to Dunstan & Short (1977) - BD maximal basis (bulb) diameter - BI bulbing index - BC basal callus - BS basal sprouting - ND bulb neck diameter     

RAPD and AFLP assessment of genetic variation in a landrace of pepper (Capsicum annuum L.), grown in North-West Italy

In several regions of Italy as well as other parts of southern Europe, the heterogeneity of the land, the climate and the soil favour the survival in cultivation of a large number of landraces specifically adapted to local conditions. Knowledge on the level and distribution of their genetic variation can help to develop appropriate strategies, in order to suistainably manage in situ these germplasm resources at risk of genetic erosion. C. annuum is an herbaceous diploid species and is considered to be self-pollinating, although different rates of out-crossing have been recorded. We used random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers to assess genetic diversity within and between five populations of a landrace of Capsicum annuum L., grown in a limited area in north-west Italy and locally known as Cuneo pepper. Partitioning the genetic variation with Shannon's diversity index revealed that 41.6% occurred between and 58.4% within populations. Analogous results were obtained when the analysis was based only on RAPD or AFLP markers. However, AFLP was more reliable, since a lower range of variation was observed among primer combinations in detecting the two components of genetic variation. Notwithstanding the rather high level of within genetic variation detected, the five populations were clearly differentiated and differed in the frequency of alleles exclusive and/or present at very low frequencies. Our results show the need for accurate estimation of allele frequencies, in order to identify populations to which priority should be given for dynamic conservation of landraces.     

Ecology of soil microflora and mycorrhizal symbionts in degraded forests at two altitudes

Summary Microbial populations were estimated in four different forest stands at different regenerational stages, two each at higher and lower altitudes. The fungal and bacterial populations showed marked seasonal variations at both altitudes. Quantitatively, the bacterial population was higher than the fungal population. Although 25 fungal species were isolated at the lower altitude, only 15 were obtained at the higher altitude. Penicillium chrysogenum and Trichoderma viride were dominant at the lower and higher altitudes, respectively. In the more degraded forest stand at the lower altitude both the fungal and the bacterial population showed a significant positive correlation with organic C (r=0.658 and 0.735, respectively), whereas in the less degraded forest stand there was a significant correlation only between the fungal population and organic C (r=0.835). At the higher altitude, however, a highly significant correlation (P<0.05) was observed between the fungal population, soil moisture and organic C in both the forest stands. Disturbance to the soil and vegetation adversely affected the microbial population, and also affected endogonaceous spores. At the lower altitude, plants in the more degraded forest stand were more mycotrophic compared to those in the less degraded stand. The level of mycorrhizal infection showed a highly positive correlation with soil moisture, organic C, total N, and available P. The spore population, however, was correlated negatively with these parameters. Three different endogonaceous genera, Glomus, Gigaspora, and Acaulospora, were identified during the course of investigation. Glomus, however, was dominant.     

Identification and overcoming barriers between Brassica rapa L. em. Metzg. and B. nigra (L.) Koch crosses for the resynthesis of B. juncea (L.) Czern.

Brassica juncea (2n = 36, AABB) is an amphidiploid derived from its diploid progenitor species B. rapa (2n = 20, AA) and B. nigra (2n = 16, BB). Resynthesis of B. juncea by exploiting the wider gene pool of the present day diploids offers a powerful tool for obtaining novel genetic variation. Hybridization between the two species is difficult because of the presence of crossability barriers. Barriers to hybridization were identified using Aniline Blue Fluorescence (ABF) method. Crosses were classified as having pre- or post-fertilization barriers based on whether less than or more than one per cent ovules showed pollen tube entry. Of the 23 crosses studied, seven crosses all with B. rapa as the female parent showed pre-fertilization barriers. Only 0 to 0.3 per cent ovules were fertilized in these crosses. The remaining 16 crosses, four with B. rapa as the female parent and 12 with B. nigra as the female parent, showed post-fertilization barriers. In crosses with pre-fertilization barriers use of bud pollination and stump pollination ensured or increased fertilization. These two simple techniques were used in combination with ovary-ovule culture to ensure recovery of hybrids. In crosses with post-fertilization barriers, ovary-ovule culture alone helped to obtain hybrids. Hybrids were obtained at higher frequency with the use of direct ovule culture compared to ovary-ovule culture. The F₁ plants obtained in vitro were multiplied on MS medium + 2 mg/l Kn + 0.2 mg/l IAA. These F₁ plants were confirmed as true hybrids through morphology, leaf isozymes and cytology. In all 17 hybrids were obtained of which three were amphidiploids.     

Characterization of Portuguese populations of <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. ssp. <Emphasis Type="Italic">sylvestris</Emphasis> (Gmelin) Hegi

Wild populations of Vitis vinifera L.␣have been located in Portugal. Morphological characterization was carried out in three populations located in Alcácer do Sal, Castelo Branco, and Montemor-o-Novo, and then compared using multivariate discriminant analysis. These populations were from three different hydrological basins, therefore cross-pollination was not possible. It was verified that in each population all plants were different. The data suggest that the frequency of female and male plants is rather variable in wild populations. The morphology of the adult leaf, from the Alcácer do Sal population, had particular features when compared with Castelo Branco and Montemor-o-Novo populations, which were more homogeneous. The length of teeth compared with width at the end of the base, and the density of prostrate hairs between and on main veins (lower side) were the variables which allowed the best discrimination among populations.     

Comparison of the genetic structure of populations of wild emmer wheat, <Emphasis Type="Italic">Triticum turgidum</Emphasis> ssp. <Emphasis Type="Italic">dicoccoides</Emphasis>, from Israel and Turkey revealed by AFLP analysis

The aim of the present study was to assess the genetic variation in several Israeli and Turkish populations of wild emmer wheat, Triticum turgidum ssp. dicoccoides, the progenitor of most domesticated wheat. Single spikes were collected in 2002 from 60 plants that grew in six different habitats in Ammiad, northeastern Israel (8–12 plants from each habitat), and in 1998 from 56 plants that grew in seven different habitats in Diyarbakir, southeastern Turkey (8 plants from each habitat). Seeds were planted in a nursery and DNA was extracted from every plant and analyzed by the fluorescent-based amplified fragment length polymorphism (AFLP) method. Seven primer combinations produced 788 discernible loci of which 48.6% were polymorphic in Israel and 40.5% in Turkey. The genetic diversity estimates P (frequency of polymorphic loci) and He (gene diversity) were higher in Ammiad than in Diyarbakir (means of P = 0.34 and He = 0.13 in Ammiad vs. P = 0.20 and He = 0.08 in Diyarbakir). Ammiad populations contained more unique alleles than Diyarbakir populations. The relative genetic diversity estimates (θ) values were 0.188 in Ammiad and 0.407 in Diyarbakir, suggesting better differentiation of the populations in Turkey. Genetic distance was larger between Israeli and Turkish populations than between populations of each country. The data indicate that the Israeli and Turkish populations are considerably diverged and that the Israeli populations are more polymorphic than the Turkish ones, having a larger within-populations genetic variation than among-populations one. The significance of the results in relation to the differentiation pattern of wild emmer in the Near East is discussed.     

Inter-simple sequence repeat (ISSR) and RAPD variation among wild barley (Hordeum. vulgare subsp. spontaneum) populations from west Turkey

Inter-Simple Sequence Repeat (ISSR) and Randomly Amplified Polymorphic DNA (RAPD) markers were used to analyze genetic distance among H. vulgare subsp. spontaneum populations from west Turkey. Fifty-five RAPD and 10 ISSR primers were used to detect variation among sample. A total of 55 polymorphic loci were found using 65 primers. Two distinct cluster groups were clearly established among populations. The minimum variation was detected between Pinarbasi and Bornova (GD = 0.192) populations and the maximum was found between Icmeler and Aydin populations (GD = 0.926). As two dominant markers, RAPD and ISSRs are effective and promising marker systems for detecting genetic variation.     

Variation in resistance to the cabbage aphid ( Brevicoryne brassicae) between and within wild and cultivated Brassica species

Seven Brassica species were evaluated for their resistance to the cabbage aphid, Brevicoryne brassicae, in a series of field experiments. Four wild Brassica species, two 8 chromosome species with similarities to the B genome of Brassica nigra (Brassica fruticulosa and Brassica spinescens) and two 9 chromosome species containing the C genome (Brassica incana and Brassica villosa) were identified as possessing consistently high levels of antibiosis mediated resistance to B. brassicae. None of the species were shown to possess consistently high levels of antixenosis resistance. In more detailed glasshouse experiments one B-like genome species, B. fruticulosa, showed considerable variation between accessions collected from different sites for resistance to B. brassicae. In addition, individual accessions of one A genome species (Brassica rapa) and one C genome species (Brassica alboglabra) were shown to be highly variable in their resistance to B. brassicae, some plants of each accession being highly resistant and others very susceptible. The implications of the variability in resistance to B. brassicae within wild Brassica species for exploitation in Brassica breeding programmes are discussed.     

Spore production by the vesicular-arbuscular mycorrhizal fungus Glomus monosporum as related to host species,root colonization and plant growth enhancement

Summary The vesicular-arbuscular mycorrhizal fungus Glomus monosporum was inoculated on grapevine (Vitis vinifera), red clover (Trifolium pratense), meadow grass (Poa pratensis) and onion (Allium cepa) as hosts in two experiments carried out in different environments. Grapevine and clover showed the largest growth response and spore production. Mycorrhizal infection was lowest in meadow grass. Very poor correlations were observed, on an overall basis, between spore production and per cent root infection or infected root length. Spore production per unit infected root length for each host species was a comparatively stable parameter; it was largest for grapevine and smallest for meadow grass in both experiments. Sporulation was positively correlated with growth enhancement by mycorrhizal plants, and growth increments per unit infected root followed the same trend as spore numbers per unit infected root, i.e. largest for grapevine and lowest for meadow-grass. It is concluded that the ability of G. monosporum to produce spores and to enhance plant growth per unit infected root length depends on the host plant species.     

The Vigna angularis complex: Genetic variation and relationships revealed by RAPD analysis, and their implications for in situ conservation and domestication

The present study, using RAPD analysis, was undertaken to characterize genetic variation in three forms of V. angularis, cultivated, wild and weedy forms, and their relationships. The materials used consisted of 171 individuals (plants) or cultivars from 23 populations including 5 wild populations, 6 weedy populations, 6 cultivated populations and 6 populations with plants having wild and weedy or intermediate morphology, denoted here as complex populations. The materials used were collected on Honshu Island, Japan and seeds collected directly from the field were germinated for DNA extraction. In addition, 6 landrace accessions of V. angularis from the genebank were also analyzed. Genetic variation was highest in the wild form (H_g= 0.132; GD = 0.388), followed by the weedy form (H_g= 0.124; GD = 0.341) and the least in the cultivated form (H_g= 0.079; GD = 0.274). Intra-population genetic variation was high in the weedy and in the wild populations. However, inter-population was greater than intra-population genetic variation for all groups of populations studied in the V. angularis complex. 93% of the total diversity in the present study was exhibited by plants from complex populations and specific RAPD bands were found in these populations. Our results provide evidence that complex populations would be a logical focus for efforts to conserve the V. angularis complex in situ. Our results suggest that weedy populations are usually an ecotype of the wild form adapted to a different habitat.     

Genetic diversity of HMW glutenin subunits in diploid,tetraploid and hexaploid <Emphasis Type="Italic">Triticum</Emphasis> species

The genetic variations of high-molecular-weight (HMW) glutenin subunits in 1051 accessions of 13 Triticum subspecies were investigated using sodium dodecyl sulfate polyacrylamide-gel electrophoresis. A total of 37 alleles were detected, resulting in 117 different allele combinations, among which 20, 68 and 29 combinations were observed in diploid, tetraploid and hexaploid wheats, respectively. Abundance and frequency of allele and combinations in tetraploid wheats were higher than these in hexaploid wheats. Allele Glu-A1c was the most frequent subunit at Glu-A1 locus in tetraploid and hexaploid wheats. Consequently, the results also suggested that the higher variations occurred at Glu-B1 locus compared to Glu-A1 and Glu-D1. Therefore, carthlicum wheat possessing the allele 1Ay could be presumed a special evolutional approach distinguished from other tetraploid species. Furthermore, this provides a convenient approach of induction of the 1Ay to common wheat through direct cross with carthlicum wheat. Alleles Glu-B1c and Glu-B1i generally absent in tetraploid wheats were also found in tetraploid wheats. Our results implied that tetraploid and hexaploid wheats were distinguished in dendrogram, whereas carthlicum and spelta wheats and however displayed the unique performance. In addition, founder effect, no-randomness of diploidization, mutation and artificial selection could cause allele distribution of HMW-GS in Triticum. All alleles of HMW-GS in Triticum could be further utilized through hybrid in the quality improvement of common wheat.     

Diversity and phylogenetic analysis in Cocos nucifera L. in Mexico

The diversity and phylogenetic analysis in 22 populations of Mexican coconut and six imported populations, were estimated using 15 enzymatic systems and the allele frequencies in: peroxidase (PER), endopeptidase (ENP), and glucose 6-Phosphate dehydrogenase (G6PD). There was very low polymorphism, not more than two alleles per locus. The Wright fixation indexes F(it) = 0.62, F(is) = 0.40, and F(st) = 0.36 indicated low total heterosygosity and low heterosygosity within populations suggesting endogamy and genetic drift, and a high diversity among populations due to differentiation between Pacific and Gulf of Mexico coastal populations. The phylogenetic tree with values for genetic distance, indicated three groups on the Pacific coast related to Rennell Tall and Polynesian Tall, and two groups on the coast of the Gulf of Mexico, one related to West African Tall and another related to Mexican Pacific coast populations. This corroborates historical antecedents and morphological and physiological patterns. The Dwarf coconuts related to the Pacific Tall populations, Rennell Tall and Polynesian Tall. There was no difference between local and imported Dwarf populations.     

Orientation behaviour of earthworms (Lumbricidae) towards different crops

Summary In an outdoor experiment the distribution of earthworms (Lumbricus spp., Allolobophora spp.) under different plant species was studied. Earthworms avoid uncovered areas, but show different reactions under vegetation. This effect reappears in the same manner every year. A particular preference was shown for clover whereas onion was least preferred. Possible reasons for this behaviour are the extent of covering, the moisture regime and exudates of the plants. According to the results obtained the deciding factor seems to be the extent of cover whereas odorous substances are of secondary importance.Dedicated to the late Prof. Dr. M.S. Ghilarov     

Powdery mildew resistance in Aegilops tauschii coss. and synthetic hexaploid wheats

Summary A collection of 400 Ae. tauschii (syn. Ae. squarrosa) Coss. accessions were screened for powdery mildew resistance based on the response patterns of 13 wheat cultivars/lines possessing major resistance genes to nine differential mildew isolates. 106 accessions showed complete resistance to all isolates, and 174 accessions revealed isolate-specific resistance, among which were 40 accessions exhibiting an identical response pattern as wheat cultivar Ulka/^*8Cc which is known to possess resistance gene Pm2. Expression of both complete and isolate-specific resistance from Ae. tauschii was observed in some synthetic hexaploid wheats derived from four mildew susceptible T. durum Desf. parents, each crossed with five to 38 resistant diploid Ae. tauschii accessions. Synthetic amphiploids involving different combinations of T. durum and Ae. tauschii generally showed a decrease in resistance compared with that expressed by the Ae. tauschii parental lines.     

Species Diversity in Wheat Landrace Populations from two Regions of Ethiopia

Wheat (Triticum spp.) landrace populations in Ethiopia are mostly species mixtures. However, no quantitative data is available with regard to their species components. We studied here 32 wheat landrace populations originating from two regions (Bale and Wello). A total of 2559 individual plants, 45–110 plants representing each population, were classified into their species components. Five tetraploid (2n = 4x = 28) and one hexaploid (2n = 6x = 42) wheat species were found in mixtures of varying proportions. These included the tetraploids Triticum durum Desf., Triticum turgidum L., Triticum aethiopicum Jakubz., Triticum polonicum L., Triticum dicoccon Schrank and the hexaploid Triticum aestivum L. Also found, however in a rare frequency, in two populations from Wollo was T. durum Desf. convar. durocompactoides Flaksb. (Triticum pyramidale Percival), which is a very dense spiked durum. Discriminant analysis using seven qualitative traits revealed 91.5% correct classification of the wheat species, beak awn and awn length with the most significant importance. Single species were found in eight of the populations; six were for T. durum and two for T. aethiopicum. Two to three species-combinations were the most frequent; a maximum of four species was recorded in one population. The highest diversity index (H′) observed was 0.44. T. durum was the most predominant species. The hexaploid T. aestivum was found in nine of the Wollo populations and, in one population, its frequency reached up to 35.5%. On altitudinal basis, no clear trend of clinal variation was observed both from the frequency distributions and H′ estimates. The results confirmed that Ethiopian wheats, despite the morphological overlaps, could be classified into their species components with high degree of certainty. For the future, therefore, genetic diversity estimations should be dissolved into their species components for more expeditious utilization and conservation of this important genetic resource.     

Conservation benefits of biological control: The recovery of a threatened plant subsequent to the introduction of a pathogen to contain an invasive tree species

Biological control using host-specific natural enemies is sometimes the only long-term and cost-effective option to contain dominant invasive alien species in natural ecosystems. To assess biocontrol success, most monitoring studies focus on the negative impacts of the released biocontrol agents on the target invasive species. Very few studies have shown the conservation benefits, i.e. their positive effects on the recovery of native species and habitats. A fungal pathogen (Colletotrichum gloeosporioides f. sp. miconiae) was successfully released on the island of Tahiti (South Pacific) to control the dominant invasive tree Miconia calvescens which forms dense monospecific stands in native rain- and cloud forests. The pathogen causes a leaf disease leading to partial (5–35%) defoliation of Miconia canopy trees. We studied the demographical parameters of the rare endemic sub-shrub Ophiorrhiza subumbellata, growing in the understory of montane cloud forests invaded by Miconia. We compared Ophiorrhiza populations in 13 plots set up in two sites located between 950 and 1000 m elevation, having the same Miconia invasion degree but different levels of leaf damage. Our results showed that, whereas the total population density of Ophiorrhiza is not affected, plants’ growth and fertility were significantly higher in more defoliated Miconia forests. A 3-year-long survey of Ophiorrhiza population at one study site indicated that the number of seedlings and juvenile plants increased, suggesting better recruitment and survival. This study demonstrates that biological control has contributed to the recovery of an endemic plant directly threatened by an invasive species, and may be considered as an important management tool for the partial restoration of native forests.