International Germplasm Research Articles

Analyzing Genetic Relationships in <I>Bombyx mori</I> Using Intersimple Sequence Repeat Amplification

Intersimple sequence repeat (ISSR) amplification was used to analyze genetic relationships among silkworm, Bombyx mori L., strains. Nineteen primers containing simple sequence repeat (SSR) motifs were tested for amplification on a panel of 42 strains, representative of the diversity of silkworm germplasm; 12 of the primers amplified distinct, reproducible bands. The primers amplified a total of 108 bands, of which 85 (78.7%) were polymorphic. The ISSR results suggested that within the dinucleotide class, the poly(CA) motif was more common than the poly(CT) motif. The ISSR amplification pattern was used to group the silkworm strains into seven subclusters based on their origin in an unweighted pair-group method with arithmetic average cluster analysis by using Nei's genetic distance. Seven major ecotypic silkworm groups were analyzed. Principal component analysis of the ISSR data supported the unweighted pair-group method with arithmetic average clustering. Therefore, ISSR amplification is a valuable method for determining genetic variability among silkworm varieties. This efficient genetic fingerprinting technique should be useful for characterizing the large numbers of silkworm strains held in national and international germplasm centers.

Analyzing Genetic Relationships in Bombyx mori Using Intersimple Sequence Repeat Amplification

Intersimple sequence repeat (ISSR) amplification was used to analyze genetic relationships among silkworm, Bombyx mori L., strains. Nineteen primers containing simple sequence repeat (SSR) motifs were tested for amplification on a panel of 42 strains, representative of the diversity of silkworm germplasm; 12 of the primers amplified distinct, reproducible bands. The primers amplified a total of 108 bands, of which 85 (78.7%) were polymorphic. The ISSR results suggested that within the dinucleotide class, the poly(CA) motif was more common than the poly(CT) motif. The ISSR amplification pattern was used to group the silkworm strains into seven subclusters based on their origin in an unweighted pair-group method with arithmetic average cluster analysis by using Nei’s genetic distance. Seven major ecotypic silkworm groups were analyzed. Principal component analysis of the ISSR data supported the unweighted pair-group method with arithmetic average clustering. Therefore, ISSR amplification is a valuable method for determining genetic variability among silkworm varieties. This efficient genetic fingerprinting technique should be useful for characterizing the large numbers of silkworm strains held in national and international germplasm centers.

AN ASSESSMENT OF GENETIC DIVERSITY WITHIN AND BETWEEN BRASSICA NAPUS AND BRASSICA JUNCEALINES FROM INTERNATIONAL GERMPLASM COLLECTIONS

Germplasm collections are valuable gene pools providing diverse genetic material that may be applied for the improvement of cultivars and advanced agronomic productivity. An assessment of genetic diversity in crop germplasm collections can assist in the choice of parents for genetic mapping populations and subsequent marker-assisted selection. Genotyping individuals and cultivars within germplasm collections can help breeders narrow the search for new alleles at loci of interest and assist in the identification of ‘perfect’ marker alleles from candidate genes that can then be introduced into new varieties along with their associated desirable traits. Genotypic information from germplasm collections can be used to assign lines and populations to heterotic groups; to study the evolutionary history of wild relatives; to verify pedigrees and fill in the gaps in incomplete pedigree or selection history and to monitor changes in allele frequencies in cultivars or populations. Towards the application of genetic diversity analysis to germplasm improvement, we have characterised within and between line genetic diversity in an international germplasm collection, consisting of over 100 B. napus and B. juncea lines, using genomic and EST (expressed sequence tag) derived Simple Sequence Repeat (SSR) molecular markers. Further genetic diversity analysis has been performed on related germplasm from 17 lines maintained in the UK along with 30 B. napus cultivars grown commercially in Australia. Analysis of the resulting data indicates clustering associated with geographical origin and breeding history as well as association with valuable agronomic traits.

Screening techniques and sources of resistance to root diseases in cool season food legumes

Soil-borne fungal diseases are among the most important factors, limiting the yield of grain legumes in many countries worldwide. Root rot, caused by Aphanomyces euteiches, Rhizoctonia solani, Fusarium solani and wilt, caused by several formae speciales of Fusarium oxysporum are the most destructive soil-borne diseases of pea, chickpea, lentil, fababean and lupin. The most effective control of these diseases is achieved through the use of resistant varieties. In this paper, recent advances in conventional and innovative screening methods for disease resistance are presented. Many grain legume accessions, which are maintained in national and international germplasm collections, have been evaluated for disease resistance and numerous resistant varieties have been released following incorporation of identified resistance genes from these sources. Recent identification of molecular markers tightly linked to resistance genes has greatly enhanced breeding programs by making marker assisted selection (MAS) possible and allowing the development of varieties with multiple disease resistance. Progress in the understanding of the biology of soil-borne fungal pathogens of grain legumes is also reviewed with particular reference to the genetic structure of their populations, diagnosis and host-pathogen interaction.

Boron deficiency in wheat: a review

Although cereals are generally considered to be insensitive to boron (B) deficiency, incidences of B deficiency have been reported from many of the world’s wheat growing countries since the 1960s. The most extensive region of B deficiency in wheat so far reported is the adjoining area of eastern Nepal, northeastern India and northwestern Bangladesh, through to southwestern China. Wheat is more prone to B deficiency than rice and maize, and some dicotyledons including soybean and mungbean. Although it has been reported to adversely affect many processes of wheat growth and development, B deficiency depresses commercial wheat yield primarily through grain set failure, which is in turn caused by male sterility. The function of wheat anthers has been found to be impaired when their B concentration per unit dry weight was 10 times that found limiting for vegetative growth. Wheat genotypes vary greatly in their adaptation to low B soils. Boron efficient genotypes may grow and yield normally on low B soils in which inefficient genotypes are so adversely affected by B deficiency that they set no grain at all. International germplasm from the International Maize and Wheat Improvement Centre (CIMMYT) on which most developing countries depend for their new wheat cultivars is largely B inefficient. Wheat production in the world’s growing areas on low B soils should greatly benefit from increasing B efficiency in internationally important germplasm. This should be highly feasible as a few B efficient advanced breeding lines have already been identified and B efficiency is under the control of major genes.

The distribution of benefits from public international germplasm banks: the case of beans in Latin America

AbstractThe unrestricted international flow of genetic resources from international genebank collections is the source of perhaps one of the greatest impacts of international agricultural research. This paper examines the distribution across countries in Latin America of benefits generated from bean genetic resources held by the International Center for Tropical Agriculture (CIAT). The genealogies of commercial bean cultivars released since 1976, containing materials from the collection, are analysed to calculate for each country the source of the genetic resources used. All countries in the region are shown to be heavily dependent on imported genetic resources for their commercial cultivars. From the available information on the economic impact of these improved bean varieties, the share of economic productivity benefits associated with imported germplasm by country of origin is calculated. The benefits received by each country from improved bean germplasm are compared with the contribution of that country's germplasm to other countries. Some of the patterns in the flow and use of genetic resources are analysed.

The distribution of benefits from public international germplasm banks: the case of beans in Latin America

The unrestricted international flow of genetic resources from international genebank collections is the source of perhaps one of the greatest impacts of international agricultural research. This paper examines the distribution across countries in Latin America of benefits generated from bean genetic resources held by the International Center for Tropical Agriculture (CIAT). The genealogies of commercial bean cultivars released since 1976, containing materials from the collection, are analysed to calculate for each country the source of the genetic resources used. All countries in the region are shown to be heavily dependent on imported genetic resources for their commercial cultivars. From the available information on the economic impact of these improved bean varieties, the share of economic productivity benefits associated with imported germplasm by country of origin is calculated. The benefits received by each country from improved bean germplasm are compared with the contribution of that country’s germplasm to other countries. Some of the patterns in the flow and use of genetic resources are analysed.

Increasing boron efficiency in international bread wheat, durum wheat, triticale and barley germplasm will boost production on soils low in boron

Boron deficiency causes grain set failure and yield loss in many of the world’s wheat growing countries. We suggest growing B efficient genotypes as a means to overcome the problem. This study evaluated international germplasm of bread wheat ( Triticum aestivum L.), durum wheat ( Triticum durum Dest.), triticale ( Triticosecale Wittmack) and barley ( Hordeum vulgare L.) for B efficiency. The first set of germplasm consisted of bread wheat, durum wheat and triticale from CIMMYT 1996/1997 nurseries and a B efficient check wheat cv. ‘Fang 60’. The lines were grown in the field on soil with 0.1 and 0.2, and 0.3 mg HWS B kg −1 for durum wheat and triticale. The grain set index (GSI, percentage grain set in the first two florets of 10 central spikelets) measured B efficiency in wheat, durum and triticale genotypes without the need for a B sufficiency control. Three-quarters of the lines tested were B inefficient, which included all of the durum wheat, 84% of the triticale and 60% of the bread wheat lines. Six of the bread wheat lines evaluated were in the same B efficient class as Fang 60. The response to low B was confirmed in a sand culture experiment without added B. Similarly high frequency of B inefficiency was found in a second set of germplasm which included bread and durum wheat, barley and triticale lines from CIMMYT and ICARDA 2000/2001 international nurseries. Incorporating the B efficiency trait in germplasm such as these, would ensure their adaptation to low B soils, and so enable their genetic potential to be fully realized in some of the world’s difficult production areas.

CONSERVATION AND SUSTAINABLE USE OF WILD SPECIES AS SOURCES OF NEW ORNAMENTALS

While only about 1-200 species are used intensively in commercial floriculture (e.g. carnations, chrysanthemums, gerbera, narcissus, orchids, tulips, lilies, roses, pansies and violas, saintpaulias, etc.) and 4-500 as house plants, several thousand species of herbs, shrubs and trees are traded commercially by nurseries and garden centres as ornamentals or amenity species. Most of these have been introduced from the wild with little selection or breeding. In Europe alone, 12 000 species are found in cultivation in general garden collections (i.e. excluding specialist collections and botanic gardens). In addition, specialist collections (often very large) of many other species and/or cultivars of groups such as orchids, bromeliads, cacti and succulents, primulas, rhododendrons, conifers and cycads are maintained in several centres such as botanic gardens and specialist nurseries, as are 'national collections' of cultivated species and cultivars in some countries. Specialist growers, both professional and amateur, also maintain collections of plants for cultivation, including, increasingly, native plants. The trade in ornamental and amenity horticulture cannot be fully estimated but runs into many billions of dollars annually and there is considerable potential for further development and the introduction of many new species into the trade. Despite this, most of the collections are ad hoc and no co-ordinated efforts have been made to ensure that adequate germplasm samples of these species are maintained for conservation purposes and few of them are represented at all adequately in seed banks. Few countries have paid much attention to germplasm needs of ornamentals and the Ornamental Plant Germplasm Center in conjunction with the USDA National Plant Germplasm System at The Ohio State University is an exception. Generally there is a serious gap in national and international germplasm strategies, which have tended to focus primarily on food plants and some forage and industrial crops. Adequate arrangements need to be put in place to ensure the long- and medium-term conservation of representative samples of the genetic diversity of ornamental species. The problems of achieving this will be discussed. In addition, a policy for the conservation of old cultivars or 'heritage' varieties of ornamentals needs to be formulated. The considerable potential for introduction of new ornamental species needs to be assessed. Consideration needs to be given to setting up a co-ordinating structure with overall responsibility for the conservation of germplasm of ornamental and amenity plants.

Evolving Political Issues Affecting International Exchange of Arachis Genetic Resources

Abstract While plant genetic resources continue to be essential for world food security, the exchange of these resources between countries has become increasingly encumbered during recent years. The free and open access to genetic resources that previously was considered the “common heritage of mankind” has been fundamentally changed by international multilateral agreements that recognize national sovereignty over genetic resources. Since the entry into force of the Convention on Biological Diversity in 1993, many countries have implemented laws regulating access to their genetic resources. The development of legislation in several countries comprising the primary areas of origin and diversity of Arachis makes issues associated with germplasm exchange particularly relevant to investigators working with peanut. This paper describes some recent USDA experiences with obtaining access in Latin American countries harboring peanut genetic resources. Also discussed are implications and prospects for future international germplasm exchange, including aspects of collaborative research and benefit sharing with germplasm donor countries. Within this new political climate, the establishment of mutually beneficial precedents for accessing foreign genetic resources will be crucial for ensuring the continued exchange, conservation, and use of Arachis germplasm in the future.

A study of genotype-isolate interaction in cacao (Theobroma cacao L.): resistance of cacao genotypes to isolates of Phytophthora palmivora.

The resistance of cacao (Theobroma cacao. L)leaves to 10 isolates of Phytophthora palmivora(Butler) Butler was investigated in 18 genotypes of cacao in three experiments. Tissue-paper-mount and punch-inoculation methods were used to distinguish between resistance at the penetration and post-penetration levels based on lesion frequency and size, respectively. There was a 5–6 fold difference in aggressiveness among isolates collected from different locations in the islands of Trinidad and Tobago for both types of resistance. However, host genotype ×isolate interaction effects were not significant for resistance at both the penetration and post-penetration levels. A strong positive relationship (r = 0.8) was observed in the abilities of isolates to effectively breach the two types of resistance. This suggests that the same isolate can be used in screening for both types of resistance. No significant relationship was found between resistance at the penetration and post-penetration levels suggesting that the resistance mechanisms were different. Subsequent experiments using a wider range of cacao genotypes from the International Germplasm Collection, Trinidad, confirmed the initial results. These experiments indicate that resistance found using one isolate would be equally valid using other isolates of Phytophthora palmivora. The implications of the findings are discussed.

New Directions for Collecting and Conserving Peanut Genetic Diversity

Abstract Existing strategies for collecting and conserving peanut genetic diversity need to be reassessed and updated in light of recent collecting efforts, technological advances, and the new political climate affecting international germplasm access and exchange. In the Americas, important taxonomic and geographical gaps in the collections still need to be filled before the full extent of peanut genetic diversity, both wild and cultivated, can be known from the crop's hemisphere of origin. Moreover, reports of peanut genetic erosion in Asia and Africa need to be investigated and addressed. The current global trend to implement national legislation regulating access to genetic resources presents new challenges for organizing and conducting plant explorations in other countries, making international partnerships more important than ever. The use of innovative new tools and methods for assessing, locating, and conserving crop genetic diversity, such as Geographical Information Systems and on-farm conservation, has recently increased. These new tools, methods, and partnerships are proposed as key elements for an updated strategy to help ensure that the unfinished work of collecting and conserving peanut diversity can be successfully continued into the 21st century.

Inter-simple sequence repeat (ISSR) amplification for analysis of microsatellite motif frequency and fingerprinting in rice (Oryza sativa L.)

Inter-simple sequence repeat (ISSR) amplification was used to analyze microsatellite motif frequency in the rice genome and to evaluate genetic diversity among rice cultivars. A total of 32 primers, containing different simple sequence repeat (SSR) motifs, were tested for amplification on a panel of 59 varieties, representative of the diversity of cultivated rice (Oryza sativa L.). The ISSR analysis provided insights into the organization, frequency and levels of polymorphism of different simple sequence repeats in rice. The more common dinucleotide motifs were more amenable to ISSR analysis than the more infrequent tri-, tetra- and penta-nucleotide motifs. The ISSR results suggested that within the dinucleotide class, the poly(GA) motif was more common than the poly(GT) motif and that the frequency and clustering of specific tri- and tetra-nucleotide simple sequence repeats was variable and motif-specific. Furthermore, trinucleotide ISSR markers were found to be less polymorphic than either dinucleotide or certain tetranucleotide ISSR markers, suggesting which motifs would be better targets for microsatellite marker development. The ISSR amplification pattern was used to group the rice genotypes by cluster analysis. These results were compared to surveys of the same varieties for amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP) and isozyme markers. The ISSR fingerprint could be used to differentiate the genotypes belonging to either Japonica or Indica sub species of cultivated rice and to dissect finer levels of diversity within each subspecies. A higher percentage of polymorphic bands was produced with the ISSR technique than the AFLP method, based on a similar PCR reaction. Therefore, ISSR amplification proved to be a valuable method for determining genetic variability among rice varieties and for rapidly identifying cultivars. This efficient genetic fingerprinting technique would be useful for characterizing the large numbers of rice accessions held in national and international germplasm centers.

Identifying international rice research spillovers in New South Wales

AbstractThe rice industry in New South Wales, Australia, has benefited from the international flow of germplasm, as have other industries. The aim in this paper is to identify those international flows, and to value their contributions to the industry. Analysis is made of the origins and Pedigrees of the rice varieties grown in New South Wales since the 1960s, and the contribution of different germplasm sources are identified, using the geometric rule of partitioning contributions. The analysis reveals that New South Wales has had a significant contribution from international sources, notably breeding programs in the USA. The analysis also reveals that the International Rice Research Institute has had no impact on the germplasm used in New South Wales rice varieties. The changes over time on the role of international germplasm flows arc also identified.

Identifying international rice research spillovers in New South Wales

Abstract The rice industry in New South Wales, Australia, has benefited from the international flow of germplasm, as have other industries. The aim in this paper is to identify those international flows, and to value their contributions to the industry. Analysis is made of the origins and pedigrees of the rice varieties grown in New South Wales since the 1960s, and the contribution of different germplasm sources are identified, using the geometric rule of partitioning contributions. The analysis reveals that New South Wales has had a significant contribution from international sources, notably breeding programs in the USA. The analysis also reveals that the International Rice Research Institute has had no impact on the germplasm used in New South Wales rice varieties. The changes over time on the role of international germplasm flows are also identified.

281 CONSERVATION OF PHASEOLUS GERMPLASM FOR THE USDA, ARS, NATIONAL PLANT GERMPLASM SYSTEM

The Phaseolus collection is the largest collection maintained at WRPIS. It numbers 11,501 accessions with 1585 accessions pending PI assignment. Over 20% of the Phaseolus accessions must be handled in special ways because of unique pollination or day length requirements. In accordance with the stated mission of the project, evolution of the bean germplasm maintenance program has included the following innovations: 1. Expanded interaction with the international germplasm centers (i.e. CIAT) and national programs. 2. As a result of interactions with the Phaseolus CAC, the increase of this genus was moved to greenhouse production exclusively. 3. A program to clean up seedborne viruses in the Phaseolus collection was established. 4. For some of the wild species, it was necessary to establish suitable and reliable alternate regeneration sites. 5. In collaboration with the Bean Improvement Cooperative (BIC) Bean Genetics Committee, WRPIS assumed responsibility for the Genetic Stocks Collection. 6. Develop a core subset of the P. vulgaris collection based on passport data, plant characters and molecular markers.

Agriculture, food and the environment

The United Nations Conference on Environment and Development alerted the world to the hazards presumptive if the planet's natural resources of land, water, air, energy and biological organisms are not protected and utilised more conservatively. UNCED declared two urgent research priorities: global climate change and genetic diversity. Excessive use of fossil fuels and a resultant atmospheric pollution forebodes higher temperatures at the earth's surface. The consequences for agriculture are unpredictable. Alternative sources of energy are described: electric motors with high-capacity batteries and high energy fly-wheels; solar-thermal and photovoltaic systems of power generation. Global population will rise to at least 8 billion (1 billion = 10 9) by 2025, a rate of growth demanding an annual increase of 3% in agricultural production. The principles of sustainable production in relation to land and water management, genetic diversity among crop species, and food science and technology are discussed. Among the many thousand crop genotypes in the international germ plasm banks, more is known about agronomic characters than about functional properties relevant to food processing. Transgenic modifications broaden the spectrum of pest resistance in crops, but too little is known of the nutritional implications. Biotechnological advances, demands for non-polluting waste disposal, consumer concerns for food safety, the need to provide food security for a global population changing in age and income distribution, offer exciting challenges to all food scientists and technologists.

In vitro tuberization in white yam (Dioscorea rotundata Poir)

Nodal cuttings of white yam were induced to produce microtubers on a MS-revised medium supplemented with various concentrations of sucrose, 20 mgl−1 L-cysteine, 0.5 mgl−1 kinetin and 0.7% agar. The frequency of tuberization was affected by the daylength, which is optimal at 12 and 16 h of light depending on the sucrose concentration. The microtubers were planted in a seed bed and grown to maturity. The importance of in vitro tuberization of yam as a means of international germplasm distribution or exchange as well as for the propagation of planting material is discussed.

Induction of in vitro tubers in a broad range of potato genotypes

This paper describes a reproducible method for the induction of in vitro potato tubers in a wide range of genotypes. These in vitro tubers could be induced in all genotypes tested and show striking similarity to field produced tubers. In vitro tubers may prove most useful as material for International germplasm distribution.

On germ plasm conservation with special reference to the genus Medicago.

As Frankel has indicated, there is ample justification for maintaining international germ plasm centers for preservation of land races and species of a genus; this would appear self-evident on the grounds that extinction involves a permanent loss of gene pools that have required from several centuries to millions of years to evolve. Monoculture is causing extinction of some Medicago species, yet all species of the genus Medicago are of economic importance. Examples are drawn from recent crosses involving wild species of this genus, and we note the rapidly increasing appreciation of the value of annual Medicago species. Their potential future use in the South Temperate Zone countries is discussed.