Tree tomato (Solanum betaceum Cav.) grafted with a wild Solanum species

Genetic Resources and Crop Evolution - Tree tomato (Solanum betaceum Cav.) is an economically important tree from the Andes. This species was grafted onto cucubo (Solanum stellatiglandulosum...     

Conserving the genetic resources of crop wild relatives in European Protected Areas

European native plant diversity is currently suffering erosion and extinction and thus, it is crucial to improve conservation strategies to maintain this essential resource. If unchecked, this genetic erosion and species extinction will cause unnecessary and irreversible harm to the economy and social well being of Europe. Much plant biodiversity is undoubtedly found in the existing 9654 European protected areas that cover 1,066,358 km², but clearly targeted and active conservation of priority plant species is required within these protected areas. To help ensure more efficient long-term sustainable conservation, a novel approach to the in situ conservation of European plants, notably crop wild relatives, is suggested. The purpose of this approach is to know what plant genetic resources (PGR) we have, where they are located and to assess whether the current network of protected areas includes a representative sample of European PGR diversity. The generation of in situ conservation and management plans for PGR populations in existing protected areas can significantly improve the present conservation status. Additionally, the identification of gaps of certain PGR in current protected areas can provide the basis for the designation of new complementary PGR in situ reserves.     

The apple genetic resources in China: The wild species and their distributions, informative characteristics and utilisation

China is the centre of origin of the genus Malus Mill. About 80% of all species of the genus have areas in this country – among them 8 newly described ones. All species are encountered, their distribution within the provinces is listed and completed by characteristics and uses.     

Identification of malodorous, a wild species allele affecting tomato aroma that was aelected against during domestication

Vegetable cultivation favored the inclusion of pleasant aromas in the produce, whereas unpleasant aromas were selected against. Introgression lines, generated by hybridization of a cultivated tomato (Lycopersicon esculentum) to its wild relative L. pennellii, were used to map quantitative trait loci (QTL) that influence tomato aroma. A marked undesirable flavor was detected by taste panelists in L. pennellii fruits and was related to an introgressed segment from the short arm of chromosome 8. Analysis of the ripe fruits' volatiles of chromosome 8 introgressed lines revealed an up to 60-fold increase in the levels of 2-phenylethanol and phenylacetaldehyde, as compared to the cultivated tomato. This effect was associated with a 10 cM segment originating from the wild species. Although 2-phenylethanol and phenylacetaldehyde have favorable contribution to tomato aroma when present at low levels, phenylacetaldehyde has a nauseating objectionable aroma when present in levels >0.005 ppm. The loss of the ability to produce high levels of phenylacetaldehyde contributed to the development of desirable aroma of the cultivated tomato. The findings provide a genetic explanation for one of the aroma changes that occurred during the domestication of the tomato.     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Diversity and genetic resources of wild <Emphasis Type="Italic">Vigna</Emphasis> species in India

Diversity in morphological characters of 206 accessions of 14 wild Vigna species from India was assessed. Of these, 12 species belonged to Asian Vigna in the subgenus Ceratotropis and two were V. vexillata and V. pilosa belonging to subgenus Plectotropis and Dolichovigna, respectively. Data on 71 morphological traits, both qualitative and quantitative, were recorded. Data on 45 qualitative and quantitative traits exhibiting higher variation were subjected to multivariate analysis for establishing species relationships and assessing the pattern of intraspecific variation. Of the three easily distinguishable groups in the subgenus Ceratotropis, all the species in mungo-radiata group, except V. khandalensis, viz. V. radiata var. sublobata, V. radiata var. setulosa, V. mungo var. silvestris and V. hainiana showed greater homology in vegetative morphology and growth habit. The species, however, differed in other plant, flower, pod and seed characteristics. Within species variation was higher in V. mungo var. silvestris populations and three distinct clusters could be identified in multivariate analysis. V. umbellata showed more similarity to V. dalzelliana than V. bourneae and V. minima in the angularis-umbellata (azuki bean) group. Within species variations was higher in V. umbellata than other species in the group. In the aconitifolia-trilobata (mothbean), V. trilobata populations, were more diverse than V. aconitifolia. The cultigens of the conspecific wild species were more robust in growth, with large vegetative parts and often of erect growth with three- to five-fold increase in seed size and seed weight, except V. aconitifolia, which has still retained the wild type morphology to a greater extent. More intensive collection, characterisation and conservation of species diversity and intraspecific variations, particularly of the close wild relatives of Asian Vigna with valuable characters such as resistance to biotic/abiotic stresses, more number of pod bearing clusters per plant etc. assumes great priority in crop improvement programmes.     

Isozyme analysis of genetic diversity in wild Sicilian populations of Brassica sect. Brassica in view of genetic resources management

In Sicily and in the small surrounding islands the section Brassica of the genus Brassica comprises five species, B. insularis Moris, B. incana Ten., B. macrocarpa Guss., B. rupestris Raf. and B. villosa Biv. These taxa represent a genetic resource as relatives of kale crops but some populations are endangered or threatened, thus isozyme analyses were performed to assess the genetic diversity degree at population and species levels in order to assist the design of conservation management programs.Eleven loci from five enzyme systems (aconitase, leucine aminopeptidase, 6-phosphogluconate dehydrogenase, phosphoglucoisomerase phosphoglucomutase) were analyzed in sixteen natural population (fifteen from Sicily, one from Calabria). Mean within-population genetic diversity was moderate (P = 41%, A = 1.54, H = 0.16). In some cases a great number of heterozygous individuals were detected, in other cases fixation index (F) deviated significantly from Hardy-Weinberg genotypic expectations.A total of 37 alleles was recognized, six of which resulted exclusive to single populations. The among-population component of the total genetic diversity (Gst mean values) for each species was 0.30–0.37, indicating genetic differentiation among populations.Among B. villosa and B. rupestris populations genetic distance values resulted rather low and they resulted high with B. incana and B. macrocarpa populations.The results are discussed with regard to the distribution of the genetic diversity level and the genetic resources management.     

Local illegal trade reveals unknown diversity and involves a high species richness of wild vascular epiphytes

Traffic of plants and animals of wild origin is a major threat to biological diversity creating a need for legal protection of traded species. Epiphytic vascular plants are a diverse guild which provides the horticultural market with many species. Many epiphytes are under protection intended to stop illegal trade at international and local levels. To measure the richness and volume of the epiphytes that are traded illegally on a local level, we monitored an illegal sale point in Xalapa, Veracruz, Mexico for 85 weeks. We recorded 27 traders, 207 species and 7598 plants. Nineteen species were known for Mexico but not native to Veracruz; two others had been collected in Veracruz but had never been reported before for Mexico. About 25% of epiphyte richness in Veracruz and 47% of the State’s epiphytic orchids are traded illegally. Most of the species traded could have been harvested in lower montane cloud forest (105 species), however all vegetation types of central Veracruz are potential epiphyte sources. Twenty-seven species protected by Mexican law were traded, along with 41 species endemic to Mexico and six endemic to Veracruz. We concluded that on a local level, the richness and volume of epiphytes illegally traded are high; in fact, the volume of orchids traded equals the annual average volume of legal Mexican orchid exports. Illegal epiphyte trade occurs worldwide, making necessary crucial increases of protective measures and the development of sustainable ways of harvesting epiphytes.     

高温逆境下嫁接番茄耐热特性研究

以赤茄、粘毛茄、北农茄砧和托鲁巴姆为砧木，研究了嫁接番茄对夏季高温的抵御能力，以及对果实品质的影响。结果表明：高温下北农茄砧嫁接番茄叶片游离脯氨酸、蛋白质的含量均较番茄自根苗多，同时POD与APX活性较高，表现出较强的抗热能力；以赤茄为砧木嫁接番茄叶片POD与APX活性较低，叶片游离脯氨酸、蛋白质的含量减少，耐热性降低。嫁接显著地提高了番茄果实有机酸含量，降低了果实蛋白质含量。嫁接对果实维生素C、还原糖含量影响较小。     

高温逆境下嫁接番茄耐热特性研究

以赤茄、粘毛茄、北农茄砧和托鲁巴姆为砧木,研究了嫁接番茄对夏季高温的抵御能力,以及对果实品质的影响。结果表明:高温下北农茄砧嫁接番茄叶片游离脯氨酸、蛋白质的含量均较番茄自根苗多,同时POD与APX活性较高,表现出较强的抗热能力;以赤茄为砧木嫁接番茄叶片POD与APX活性较低,叶片游离脯氨酸、蛋白质的含量减少,耐热性降低。嫁接显著地提高了番茄果实有机酸含量,降低了果实蛋白质含量。嫁接对果实维生素C、还原糖含量影响较小。     

Introduction to the wild resources of the genus Boehmeria Jacq. in China

China, the native home of ramie (Boehmeria nivea (L.) Gaud. var. nivea), possesses many wild species in the genus Boehmeria Jacq., including many those rare valuables in some characteristics such as stress resistance and fiber qualities that can be used for biological engineering, genetics and breeding research. From 1995 to 1999, 130 samples of the genus Boehmeria that belong to 22 species and 6 varieties, were collected in 34 counties of 14 provinces in China in the region of N18.8–34.2° and E101–121°. The gene pool of wild species of the genus Boehmeria was constructed at Yichun, Jiangxi Province and 77 samples belonging to 8 species and 4 varieties were conserved alive. The collected species are classified into 5 sections i.e. Boehmeria, Tilocnide Bl., Zollingerianae Satake, Phyllostachys W. T. Wang and Duretia Bl., according to the morphology. They may also be divided into hygric type, moderately hygric type, semi-shade-hygrophyte and xeromorphy, based on their ecological adaptability and primitive growing circumstances. The distribution of the wild species and populations in the genus Boehmeria is related to the altitude.     

Identification of the lentil's wild genetic stock

The origin of lentil from the taxon Lens culinaris subsp. orientalis has been proved by morphological evidence and breeding experiments. This wild form exhibits variation in many characters and is distributed over a vast area from the Middle-East to central Asia. Characters that are polymorphic in the wild progenitor but monomorphic in the cultigen can be utilized for better identification of the genetic stock which gave rise to the domesticated lentil. Three characters of that kind have been identified in lentil: chromosomal architecture, crossability potential and restriction pattern of chloroplast DNA. Nearly all accessions of the cultivated lentil tested to these three characters have been found monomorphic, but considerable polymorphism exists in the wild accessions. Three subsp. orientalis accessions have been shown to share the above characters with the cultigen and hence can be regarded as members of the genetic stock from which lentil was domesticated. These three accessions originated from eastern Turkey and northern Syria.     

Genetic diversity of Fagopyrum homotropicum, a wild species related to common buckwheat

Nineteen natural populations of Fagopyrum homotropicum, a self-fertilizing close relative of common buckwheat, from the Yunnan and Sichuan provinces of China were investigated for their chromosome number and allozyme variation at 16 loci of 11 enzymes. Three populations, 'Deqin', 'Zhongdian', and 'Xiancheng', were revealed to be allotetraploid. Judging from allozyme constitution of the tetraploid and their possible progenitors, diploid progenitors are probably the diploid population of F. homotropicum from Lijiang and a natural population of F. esculentum ssp. ancestralis. Diploid populations of F. homotropicum are fixed for a given allele at almost all isozyme loci. Allozyme variation has been maintained in natural populations mainly by fixing different alleles in different populations, as they are highly differentiated among the populations (G_st = 0.969). The position of populations in the phylogenetic tree constructed from genetic distance nearly corresponded with the geographical position of the populations.     

Identification of an allele attributable to formation of cucumber-like flavor in wild tomato species (Solanum pennellii) that was inactivated during domestication

Carbon 6 (C6)-aldehydes formed by fatty acid 13-hydroperoxide lyase (13HPL) specific to fatty acid 13-hydroperoxides (13-HPO) are important flavor constituents in fresh tomato fruits. C9-aldehydes are usually formed by 9/13HPL showing dual specificity to 9- and 13-HPOs and are scarcely found in tomato fruits. Mature red fruits of one of the introgression lines, IL1-4, generated by hybridization of a cultivated tomato (Solanum lycopersicon) to its wild relative Solanum pennellii, form high amounts of C9-aldehydes upon homogenization. The IL1-4 fruits showed high 9/13HPL activity. One of the genes isolated from IL1-4 showed a high similarity to plant 9/13HPLs. Recombinant proteins expressed in Escherichia coli showed 9/13HPL activity. Cleaved amplified polymorphic sequence analyses indicated that the gene was specific to IL1-4 and S. pennellii. S. lycopersicon had a gene having high similarity to the S. pennellii gene. It was absent in IL1-4. Among the differences of amino acid residues found between the two genes, a Cys to Ser exchange may be responsible for the inactivation of resultant protein product of S. lycopersicon gene because the Cys is an essential amino acid residue for HPL activity. From these observations, it could be assumed that a tomato gene corresponding to S. pennellii 9/13HPL gene had been inactivated through domestication of tomatoes.     

Detection of adult-plant resistance to Puccinia triticina in a collection of wild Triticum species

Three hundred and fifty three Triticum accessions, several also classified as Aegilops and comprising 13 diploid, tetraploid or hexaploid species, were screened for seedling and adult-plant resistance to Puccinia triticina Eriks. using a mixture of pathotypes UVPrt2, 3, 9 and 13. Seedlings were spray-inoculated with a suspension of freshly collected urediospores in distilled water containing Tween 20^® seven days after planting. Infection types (ITs) were scored 10 days post-inoculation (d.p.i.). Fully expanded flag leaves were inoculated and ITs and leaf rust severity were scored 16 d.p.i. One hundred and eighty two of the accessions were resistant to moderately resistant in the adult stage, whereas 126 were resistant or moderately resistant as seedlings to the pathotype mixture. Hypersensitive adult-plant resistance was particularly apparent in lines of T. timopheevii, T. sharonense, T. longissimum, T. searsii and T. turgidum. In T. turgidum, which comprised 272 accessions, approximately 44% of the adult plants were resistant to moderately resistant compared to 28% of the seedlings. The expression of these adult-plant resistances varied between hypersensitive flecking of flag leaves, and small pustules commonly associated with chlorosis and/or necrosis of leaf tissue. Partial resistance, expressed by small pustules without any apparent chlorosis, was observed in species such as T. tauschii, T. turgidum ssp. durum and T. turgidum ssp. pyramidale.     

Molecular characterization of mulberry genetic resources indigenous to India

Mulberry (Morus L.) is essential for the sericulture industry as the primary feed for the silkworm Bombyx mori L. in India, with its long tradition of practicing sericulture, has a large number of indigenous cultivars. Since knowledge on the genetic divergence of these cultivars/varieties is essential for proper conservation and utilization, Inter Simple Sequence Repeat (ISSR) profiling was employed to assess genetic relationships among 34 mulberry accessions, collected from different regions of India. By using 12 ISSR primers, which produced 72 markers displaying a high degree of polymorphism (94.4%), genetic dissimilarity coefficients were calculated for each pair of the accessions and clustering of the accessions with Unweighted Pair Group Method using Arithmetic average (UPGMA) analysis was done to unravel the genetic diversity among the accessions. The dissimilarity coefficients varied from 0.111 to 0.692. UPGMA analysis generated a dendrogram with six groups and five isolates. Clustering of the accessions did not correspond with the information on the geographic origin of many of the accessions. Two-dimensional representations of the relative positions of the accessions with regards to divergence using the first two canonical variates as co-ordinate axes revealed considerable variability among the cases in each group. Further, Discriminant Function Analysis (DFA) showed changes in the geographic origin of 11 accessions and species status of 20 accessions.     

The flavonoid content in leaves and inflorescences of the wild perennial Fagopyrum cymosum complex

The Fagopyrum cymosum complex is a group of wild perennial buckwheats which includes the diploid species F. megaspartanium Q. F. Chen and F. pilus Q. F. Chen as well as the allotetraploid species F. cymosum (Trev.) Meisn. The flavonoid content in leaves and inflorescences of the accessions of the F. cymosum complex native to Guizhou, Yunnan, Sichuan, Hunan, Hubei, and Tibet has been studied by means of the spectrophotometry and high-performance liquid chromatography. The results showed that there are significant differences of flavonoid content among different species, different accessions and different plants. The average flavonoid content of leaves of F. megaspartanium is higher than that of F. pilus and of F. cymosum. The average flavonoid content of inflorescences of F. megaspartanium is higher than that of F. pilus. The results also showed that the flavonoid content in inflorescences was significantly higher than that in leaves, and that they have positive relationships to each other. There is a significant difference of rutin content between leaves and inflorescences, but there is no significant relationship to each other. There is also no significant relationship between leaf rutin contents and leaf flavonoid contents, but significant positive relationship between inflorescence rutin contents and inflorescence flavonoid contents.     

Induced mutagenesis for genetic improvement of Allium genetic resources: a comprehensive review

Genetic Resources and Crop Evolution - The genus Allium is one of the largest monocotyledon genera having 1000 designated species with commercial and economic significance. Allium cepa L. (onion)...     

Towards a methodology for on-farm conservation of plant genetic resources

The signing of the Convention on Biological Diversity at the ``Earth Summit' in 1992, its ratification and its subsequent entering into force have highlighted the need for an approach to biodiversity conservation that employs both ex situ and in situ techniques in a complementary manner. Though much research has focused on ex situ techniques, less progress has been made in developing methodologies for the conservation of genetic diversity in situ. The definition of in situ conservation used in the Convention on Biological Diversity encompasses two distinct processes: conservation of wild species in genetic reserves and of crops on-farm. Of these two, the latter, where the genetic diversity of crop land races is conserved within traditional farming systems, has been the less studied and remains less well understood. While there are still relatively few practical examples of on-farm genetic resources conservation, most genetic diversity of immediate and potential use to plant breeders is found among land races, and there is evidence that it is being rapidly eroded. This paper attempts to set on-farm conservation within the context of plant genetic resource conservation as a whole, to introduces a possible generalised model for the conservation of genetic diversity on-farm and to promote debate around the science of on-farm conservation.