Genetic resources of <Emphasis Type="Italic">Prunus</Emphasis> (Rosaceae) in India

The genetic diversity in genus Prunus is mainly confined to temperate regions of Himalaya and to a lesser extent in the sub-montane and hilly regions of peninsular India. The cultivated and wild species of Prunus have tremendous potential for improvement and utilization. This paper includes the genetic resources of cultivated and wild useful species of Prunus in India with emphasis on their distribution, potential traits/ useful characteristics and utilization. The information on potential genetic resources of Prunus would be helpful in collection, evaluation, conservation and utilization of species.     

Multivariate analysis of Prunus subgen. Cerasus germplasm in Iran using morphological variables

Knowledge of relationships among the cultivated and wild species of Cerasus, a subgenus of Prunus L., is important for recognizing gene pools, identifying pitfalls in germplasm collections and developing effective conservation and management strategies. In this study, morphological characterization of wild Cerasus subgenus species naturally growing in Iran, including P. avium L. (mazzard), P. mahaleb L., P. brachypetala Boiss., P. incana Pall., P. yazdiana Mozaff., P. microcarpa Boiss. subsp. microcarpa, P. microcarpa Boiss. subsp. diffusa and P. pseudoprostrata Pojark. and three commercial species, sweet cherry (P. avium L.), sour cherry (P. cerasus L.) and duke cherry (P. × gondouinii Rehd.) was investigated. Twenty-nine variables were recorded in 95 accessions of these species to detect similarities among them. All studied characteristics were showing a high degree of variability, but it was highly pronounced for plant height, leaf characters especially for dimensions and pubescence as well as for petiole and peduncle length. The majority of significant correlation coefficients were found in the characteristics representing plant size and growth habit with leaf size. Principal component analysis was performed for phenotypical diversity determination and grouping of species. Characters with high discriminating values were those related to growth habit, height, compactness, trunk diameter, leaf dimensions, petiole length, leaf tip and serration, flower color, peduncle length, fruit shape and stone shape. Based on the cluster analysis, species included in two main clusters, first those with large structure (sweet, sour and duke cherries, mazzard and mahaleb), second the other species with small structure which might be potentially suitable for rootstock breeding programs. Scatter plot using two first factors also confirmed the grouping by cluster analysis. The conservation of the highly diverse native populations of Iranian wild Cerasus species is recommended.     

Observations on the geographic distribution, ecology and conservation status of several Phaseolus bean species in Costa Rica

Interest in bean genetic resources of Central America has resumed because of disease pressures (e.g., web blight, BGMV) and limitations of current bean varieties. As most of the diversity in landraces has been explored, focus is now on the exploration of wild forms of the primary gene pool and wild species of the secondary gene pool. A germplasm collection was carried out in the field and resulted in the collection of 29 wild populations for six Phaseolus species; it complemented field work done in 1987. Nine more populations were found for P. costaricensis, 10 for wild P. lunatus, one for P. oligospermus, one for P. tuerckheimii, four for wild P. vulgaris and four for P. xanthotrichus. Ninety-three herbarium voucher specimens were collected for 19 populations of the six species (deposited at CR). These results confirm the presence of wild P. vulgaris on both slopes of the central valley of Costa Rica, namely in the life zones bh-MB and bmh-P, and of P. costaricensis in the life zone bmh-MB. These life zones of limited range in Costa Rica have been heavily modified, thus fully justifying the germplasm collection for ex situ conservation. For both species the range of distribution in Costa Rica has been almost completely sampled. The life characteristics of each species that are relevant for their conservation in situ are briefly reviewed. Distribution ranges of each wild bean species are compared with the present extension of national parks, protected areas and fauna/flora sanctuaries, and suggestions for expanding such protected areas are made.     

Realizing value of genetic resources of <Emphasis Type="Italic">Allium</Emphasis> in India

The genetic resources of Allium in India are potential source of genes for widening the crop genetic base. Despite their high economic value, limited number of germplasm accessions of wild species have been collected and conserved mainly due to difficult access to areas of occurrence. The present work mainly highlights information on species diversity distribution and utilization of wild Allium species to assess the value of Indian germplasm and prioritization for future collection and conservation programmes.     

Collection of Lupinus angustifolius L. Germplasm and Characterisation of Morphological and Molecular Diversity

Lupinus angustifolius L. is a Mediterranean species, domesticated in the 20th century, representing an important grain legume crop in Australia and other countries. This work is focused on the collection of wild germplasm and on the characterisation of morphological and molecular diversity of germplasm accessions. It reports the collection of 81 wild L. angustifolius accessions from the South and Centre of Portugal, available at the ‘Instituto Superior de Agronomia Gene Bank’, with subsequent morphological and molecular characterisation of a selection of these and other accessions. A multivariate analysis of morphological traits on 88 L. angustifolius accessions (including 59 wild Portuguese accessions, 15 cultivars and 14 breeding lines) showed a cline of variation on wild germplasm, with plants from Southern Portugal characterised by earlier flowering, higher vegetative development and larger seeds. AFLP and ISSR molecular markers grouped modern cultivars as sub-clusters within the wider diversity of wild germplasm, revealing the narrow pool of genetic diversity on which domesticated accessions are based. The importance of preserving, characterising and using wild genetic resources for L. angustifolius crop improvement is outlined by the results obtained.     

Chloroplast DNA study in sweet cherry cultivars (Prunus avium L.) using PCR-RFLP method

The chloroplast DNA of 96 sweet cherry cultivars (Prunus avium L.) and five cultivars of sour cherry (P. cerasus L.) were analysed to reveal their haplotypes using PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphism) method. The main advantages of the PCR-RFLP technique are: resolutive, time and cost effective and reproducible. Approximately 9.6% of the chloroplast genome was analysed, using six universal primer pairs and two restriction enzymes. All the mutations detected were insertion-deletions, ranging between 5–30 bp. The combination of all the mutations resulted in three haplotypes (H1, H2 and H3) in the 96 sweet cherry cultivars and a single haplotype (H4) in the five cultivars of sour cherry. The cpDNA polymorphism determined by PCR-RFLP markers helped to understand the maternal inheritance of chloroplast genome in sweet cherry, clearly distinguished the sour from the sweet cherry, and supported that P. avium is not the maternal species of P. cerasus.     

Characterisation of germplasm accessions of Napier grass (pennisetum purpureum and P. purpureum×P. glaucum Hybrids) and comparison with farm clones using RAPD

Fifty six germplasm accessions of the important East African fodder crop Napier grass, Pennisetum purpureum, and its hybrids with P. glaucum, were characterised using 67 random amplified polymorphic DNA (RAPD) fragments. No or very low intra-accession variation was found for 49 of the accessions examined, confirming field observations that this species is predominantly clonally propagated. Comparison of intra and inter-accession variation identified several groups of identical/similar accessions that could be targeted if the collection is to be rationalised, and also highlighted two misplantings of germplasm material during transfer to a field trial site. A neighbour joining dendrogram of Jaccard's similarity estimates, clearly separated 50 accessions of P. purpureum from three P. glaucum individuals, and placed six hybrid accessions in an intermediate position. These groupings were well supported by a nested AMOVA (P<0.001; 29.5% of total variance due to taxonomic delineation). The main group of P. purpureum individuals could be further differentiated into five sub-groups (designated East Africa, Southern Africa, USA1, USA2 and Miscellaneous, to reflect the majority membership of sub-groups) and examination of the within P. purpureum component of the nested AMOVA, found them to be significantly different (P<0.001; 18.8% of variance). Genetic diversity across all accessions was found to be fairly high (Shannon's diversity index 0.306) and thus the collection probably represents a wide genetic base for this species. In addition to germplasm accessions, 25 Kenyan farm clones were also analysed. A principal coordinate analysis found that all but one of the clones clustered with the main P. purpureum group of accessions, indicating that the majority are probably not interspecific hybrids. The origin and pedigree of clones is discussed based on genetic similarity amongst clones and to germplasm accessions.     

Selecting in situ conservation sites for grape genetic resources in the USA

Previously, there has not been any in situ conservation sites for crop germplasm within the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Plant Germplasm System (NPGS). Using morphologic and molecular (SSR markers) techniques, we assessed the genetic variation present in populations of rock grape (Vitis rupestris Scheele), a native American grape species, throughout its range. We identified seven in situ conservation sites for rock grape using a strategy based on morphologic and molecular data, taxonomic information, population size and integrity, and landholder commitment. In collaboration with federal and state landholding agencies, we have established the first NPGS in situ conservation sites for American wild relatives of a crop.     

Isozyme variation in Passiflora subgenera Tacsonia and Manicata. Relationships between cultivated and wild species

Isozyme variation was studied in 87 plants from 32 cultivated and wild accessions of banana passion fruit (P. tripartita var. mollissima, P. tripartita var. tripartita, P. tarminiana, and P. mixta), rosy passion fruit (P. cumbalensis), tin-tin (P. pinnatistipula), gulián (P. ampullacea), P. antioquensis, P. bracteosa, and P. manicata, from the Andes of Venezuela, Colombia, and Ecuador. Six polymorphic enzyme systems (IDH, PGDH, PGM, DIA, PRX, and ACP) revealed 31 zymotypes characterized by the presence or absence of 31 electromorphs. Cluster analysis separated clearly the accessions of P. tarminiana, P. tripartita, P. mixta, and P. cumbalensis from the less typical species of subgenus Tacsonia, which is consistent with morphological evidence. P. mixta showed the highest intraspecific variation and the closest affinity with P. tripartita. The accessions of these two species formed two clusters, one dominated by Colombian genotypes and the other dominated by Ecuadorian genotypes. One of the P. tripartita var. mollissima accessions clustered close to P. tarminiana accessions. The affinity between these three species is particularly interesting for conservation and use of banana passion fruit genetic resources. All the other species formed monospecific clusters.     

Genetic variation in germplasm accessions of Secale vavilovii Grossh

Summary The accurate identification and classification of wild species enhance the utilization of potential plant genetic resources. The wild rye species Secale vavilovii Grossh. may serve to broaden the genetic variation in cultivated rye, S. cereale. The combined analyses of cytological, isozymic and other genetic characteristics in the present study revealed that of the fourteen rye accessions designated as S. vavilovii, only three accessions were correctly classified. Thus it is essential to increase multidisciplinary, international research and collaboration to aid in the classification and utilization of the yet untapped plant germplasm.     

Genetic Diversity in Accessions of Wild Rice Oryza granulata from South and Southeast Asia

Oryza granulata, an upland wild rice species, represents an unique germplasm for possessing abilities of tolerance to shade and drought, immune to bacterial blight and resistance to brown planthopper. Although low degree of genetic variability has been revealed within its populations, little genetic information at the species level is available in determining rational conservation strategies. Here we used dominant DNA marker random amplified polymorphism DNA (RAPD) to assess the genetic variability among 23 accessions of O. granulata that collected from main distribution areas worldwide. Twenty decamer primers generated a total of 243 bands, with 83.5% of them (203 bands) being polymorphic. Calculation of Shannon index of diversity revealed an average value of 0.42 ± 0.25, indicating that O. granulata maintains a relatively high degree of genetic diversity on the species level. Analysis of genetic dissimilarity (GD) showed that genetic differentiation occurred among studied accessions, which supports the feasibility of current ex situ conservation strategies. We also suggested that information based on population studies, which could be achieved by international co-operation, is needed to conserve this widespread germplasm more effectively.     

Using SSR markers to determine the population genetic structure of wild apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) in the Ily Valley of West China

Genetic structure of three wild populations (Xinyuan, Gongliu and Daxigou) of apricot in the Ily Valley, Xinjiang Uygur Autonomous Region of China, was investigated with microsatellite (simple sequence repeat, SSR) markers. The higher polymorphism and greater transportability of these markers between Prunus species proved SSR markers were much efficient for conducting genetic diversity studies in wild apricot. Nei's gene diversity (He) and Shannon's index of diversity (I) were 0.287 and 0.458, respectively. This indicated that the wild apricot in the Ily Valley still maintained a relatively high level of diversity. The Gst of 0.137 and Fst of 0.164 revealed that genetic variation mainly resided among individuals within populations (83.6–86.3%). Population differentiation could also be found according to the distribution of SSR alleles between the populations. Mantel test showed the genetic distance between populations was significantly correlated to the geographical distance. The modest amount of gene flow (2.684) would reduce the disjunction between wild apricots. The long-distance dispersal of pollen by insects was probably the main way of gene flow between populations. Based on the study of population genetic structure, an effective conservation strategy of the species was discussed.     

Crossability relationships between the common potato, Solanum tuberosum spp. tuberosum, and its wild diploid relatives S. kurtzianum and S. ruiz-lealii

The common potato, Solanum tuberosum spp. tuberosum (tbr), is a tetraploid species with a narrow genetic base, but with a large number of related species that harbor great genetic diversity for numerous characters of agronomic interest. S. kurtzianum (ktz) and S. ruiz-lealii (rzl) are wild diploid relatives with potential resistance to adverse biotic and abiotic factors. To evaluate if this wild germplasm can be incorporated by conventional crosses into the tbr gene pool, pollen-pistil compatibility relations and seed set in interspecific crosses with tbr were investigated. In 4x tbr × 2x ktz crosses and the reciprocals, 89% and 52.2% of genotypic combinations (respectively) were compatible at the pollen-pistil level. Seeds were obtained from some genotypic combinations in both directions of the cross, suggesting that functional 2n gametes might be produced by particular ktz genotypes. In 2x rzl × 4x tbr crosses and their reciprocals, 35% and 11.7% (respectively) of the genotypic combinations were compatible at the pollen-pistil level, but no seeds were obtained. These results indicate that the reproductive isolation between 4x tbr and 2x ktz is incomplete, and that gene exchange between them is feasible. Moreover, further studies will have to be carried out with rzl to ascertain its crossability with 4x tbr.     

A phenetic analysis of morphological variation in Citrullus lanatus in Namibia

Morphological data recorded from field trials using Citrullus lanatus germplasm collected in Namibia were used to analyse and compare the various morphotypes of this species. The experiment comprised wild types and local landraces as well as commercial cultivars. Cluster analysis supported the indigenous classification system used in Namibia, in which Citrullus types are distinguished based on gross morphology, ecology and usage and grouped into seed, cooking and fresh-eating (watermelon) types. Commercial watermelon cultivars formed a distinct cluster. Wide variation was found within the local types whereas the genetic basis of the commercial type appears to be narrow. The commercial cultivars were most closely related to local watermelon types and more distantly related to the wild types, whereas the cooking melons form an intermediate group.     

Analysis of the geographic distribution and relationships among Peruvian wild species of <Emphasis Type="Italic">Arracacia</Emphasis>

Relationships between Arracacia species were studied according to 28 morphological discriminant characters, in 90 accessions: 83 Arracacia (Arracacia elata, A. incisa and A. xanthorrhiza), and seven accessions of Neonelsonia acuminata, which has been confused with A. elata. The geographic distribution of the Arracacia species was determined from the passport data of the 90 accessions. A. elata was clearly differentiated from N. acuminata according to morphological characteristics. The species A. incisa was more closely related to A. xanthorrhiza. Within A. xanthorrhiza two forms, monocarpic, and polycarpic, were identified. The distribution of wild Arracacia species in Peru is characterized by two main ecological zones: (1) a dry zone, like the western Yunga and western and inter-Andean valleys of the Quechua region (with seasonal rain from November to March), where the species A. incisa and A. xanthorrhiza are present, and (2) a humid zone, like the Eastern Quechua where A. elata is adapted. These informations could be useful to establish strategies for in situ and ex situ conservation and management of germplasm.     

Identification of duplicates and fingerprinting of primary and secondary wild annual <Emphasis Type="Italic">Cicer</Emphasis> gene pools using AFLP markers

Wild annual Cicer gene pools contain valuable germplasm for chickpea improvement programs. Previous research showed that duplication might exist in accessions collected from these gene pools, which would hinder chickpea breeding and related research. AFLP (amplified fragment length polymorphism) markers were used to fingerprint the world collections of the primary and secondary gene pools including C. reticulatum Lad., C. bijugum K.H. Rech., C. judaicum Boiss. and C. pinnatifidum Jaub. et Sp. Duplicates were detected in a total of 24 accessions in both the gene pools, highlighting the necessity to fingerprint the germplasm. Genotypic difference was detected as gene pool specific, species specific and accession specific AFLP markers. These were developed into fingerprinting keys for accession identification between and within species and gene pools. Use of AFLP markers to detect duplicates and to identify accessions is a reliable method which will assist in the characterisation and use of wild annual Cicer germplasm in chickpea improvement programs. We recommend the procedure presented in this paper as a standard approach for the precise genetic identification and characterisation of future world collections of wild Cicer, to keep germplasm integrity and to benefit chickpea breeding and related research programs.