Rodomiro Ortiz

Prospects for using transgenic resistance to insects in crop improvement.

Integrated pest management has historically placed great hopes on host plant resistance. However, conventional host-plant resistance to insects involves quantitative traits at several loci. As a result, the progress has been slow and difficult to achieve. With the advent of genetic transformation techniques, it has become possible to clone and insert genes into the crop plants to confer resistance to insect pests. Resistance to insects has been demonstrated in transgenic plants expressing genes for δ δ-endotoxins from Bacillus thuringiensis (Bt), protease inhibitors, enzymes and plant lectins. Most of the plant derived genes produce chronic rather than toxic effects and some insect pests are not sensitive to some of these factors. The potential of plant derived genes can be realised by deploying them in combination with host plant resistance and exotic genes. Genes conferring resistance to insects have been inserted into crop plants such as maize, cotton, potato, tobacco, potatoes, rice, broccoli, lettuce, walnuts, apples, alfalfa and soybean. Genetically transformed crops with Bt genes have been deployed for cultivation in USA, China and Australia. However, very little has been done to use this technology for improving crop production in the harsh environments of the tropics, where the need for increasing food production is most urgent. International agricultural research centres, advanced research institutes and the seed sector should make an effort to use these new tools for increasing food

Program for the application of genetic transformation for crop improvement in the semi-arid tropics

SummaryThe semi-arid tropics are characterized by unpredictable weather, limited and erratic rainfall and nutrient-poor soils and suffer from a host of agricultural constraints Several diseases, insect pests and drought affect crop productivity. Developing stress-resistant crops has been a worthwhile activity of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Mandated crops of ICRISAT, including groundnut, pigeonpea, chickpea, sorghum and pearl millet, are the main staple foods for nearly one billion people in the semi-arid tropics. Genetic transformation provides a complementary means for the genetic betterment of the genome of these crops. Judicious application of biotechnological tools holds great potential for alleviating some of the major constraints to productivity of these crops in the agricultural systems of the semi arid tropics. This article reviews plant genetic engineering in relation to its applications in genetic enhancement and the improvement of important crops of the semi-arid tropics. For the benefit of nonbiotechnologists, a brief review of technical aspects of plant genetic engineering is also included.

Phenotypic diversity for morphological and agronomic characteristics in chickpea core collection

The chickpea (Cicer arietinum L.) core collection consists of 1956accessions, of which 1465 are desi, 433 kabuli, and 58 intermediate types. This core collection was evaluated for 7 morphological descriptors and 15agronomic characteristics to estimate phenotypic diversity. All the three groups differed significantly for flower colour, plant colour, dots on seed testa, seed testa texture, plant width, days to maturity, pods per plant,100-seed weight and plot yield. The kabuli and intermediate types were not significantly different for growth habit and seed colour, they differed,however, significantly from desi types for both traits. Desi, kabuli, and intermediate types were significantly different for plant width, days to maturity, pods per plant, 100-seed weight, and plot yield. Kabuli plants have broad plant width, matured late, have lowest average number of pods,highest 100-seed weight, and lowest plot yield. There were significant phenotypic correlations among the various characteristics. Two of these,between days to 50% flowering and flowering duration and between pod number and plant yield, explained 50% variation in the other trait in all three groups. Principal component analysis showed that days to 50%flowering, plant width, apical secondary branches, tertiary branches, dots on seed testa, 100-seed weight, flowering duration, basal secondary branches, seed colour, and seed testa texture were important traits in explaining multivariate polymorphism. Growth habit and basal primary branches did not significantly account for variation in the first five principal components of desi, kabuli, and intermediate types as well as for the entire core collection, indicating their low importance as chickpea descriptors. The average phenotypic diversity index was highest in the intermediate types(0.2653) and lowest in the kabuli types (0.1490). The Shannon-Weaver diversity index varied among traits between the three groups, and the diversity within a group depended upon the traits recorded.

Selecting a Solanum tuberosum subsp. andigena core collection using morphological, geographical, disease and pest descriptors.

One of the largest and most diverse clonally propagated potato collections of cultivated potato species is maintained at the International Potato Center (CIP). Almost 75% of this collection isS. tuberosum subsp.andigena (hereafterandigena) cultivars. The first step to select a core collection of this subspecies was to identify duplicate accessions of the same cultivar using comparisons of morphological characters and electrophoretic banding patterns of total proteins and esterases. This reduced the number of accessions in the collection from 10,722 to 2,379. The number of accessions of the same cultivar in the original collection ranged from 1 to 276. This is a report on the selection of a core from the 2,379 morphologically different cultivars using morphological, geographical, and evaluation data. A total of 25 morphological descriptors were scored from all 2,379andigena cultivars. A phenogram was constructed from these data using a simple matching coefficient and the unweighted pair group method using arithmetic averages. We decided to include in the core a proportional sample consisting of approximately the square root of the number of accessions from each first geographical division (state, department, or province) of countries whereandigena was collected. Accessions were chosen first to represent the widest morphological diversity and to maximize geographical representation of the clusters distributed on the main branches of the morphological phenogram. Second, the representative accession of each cluster was also chosen considering data on resistance to diseases and pests, dry matter content, and number of duplicate accessions identified in the original collection. The resulting core has 306 accessions (12.86%) from eight countries from Mexico to Argentina. The full breeding potential of Andean farmerselected potato cultivars that have been maintained for centuries in their center of diversity remains unknown. A thorough evaluation of their reaction to diseases and pests and other desirable traits is now feasible because the selectedandigena core set covers the broadest genetic base that is available in ex situ conservation.ResumenUna de las más grandes y diversas colecciones de especies cultivadas de papa se conserva clonalmente en el Centro Internacional de la Papa (CIP). Casi el 75% de esta colección son cultivares deS. tuberosum subsp.andigena (en adelanteandigena). El primer paso para seleccionar una colección representativa de esta subspecie fue identificar las accesiones duplicadas del mismo cultivar utilizando comparaciones de caracteristicas morfológicas y de sus patrones de bandas electroforéticas de proteínas y esterasas totales. Esto redujo el número de entradas en la colección de 10,722 a 2,379. El número de entradas del mismo cultivar fluctuó entre 1 y 276. Este es un reporte sobre la selección de una colección representativa de los 2,379 cultivares morfológicamente diferentes, usando datos morfológicos, geográficos y de evaluatión. De los 2,379 cultivaresandigena, se registraron datos de un total de 25 descriptores morfológicos. Con estos datos se construyó un dendograma utilizando el coeficiente de correspondencia simple y el método de comparación de promedios aritméticos simple. Nosotros decidimos incluir en la colección representativa, una muestra proporcional que fuera aproximadamente igual a la raíz cuadrada del número de entradas de la primera división geográfica (estado, departamento o provincia) de los países donde se hicieron colectas deandigena. Las entradas seleccionadas deberían representar la más amplia diversidad morfologica y maximizar la representatión geográfica de acuerdo a la distribución de los conglomerados principales del dendograma morfológico. Segundo, las entradas representativas de cada conglomerado también se escogieron considerando los datos sobre la resistencia a las enfermedades y plagas, el contenido de materia seca y el número de entradas duplicadas identificadas en la colección original. La colección representativa resultante tiene 306 cultivares (12,86%) de ocho países desde Mexico a Argentina. El potential de mejoramiento de los cultivares de papa seleccionados por agricultores que se han conservado durante siglos en su centro de diversidad, permanece aún casi desconocido. Una evaluación minuciosa de sus reacciones a las enfermedades, plagas y otras características deseables para el mejoramiento del cultivo de la papa es ahora factible, porque la colección representativa deandigena que se ha seleccionado abarca la base genética más amplia que está conservada ex situ.

Genetic analysis of protoplast regeneration ability in Brassica oleracea

In Brassica oleracea L., plant regeneration from protoplasts is genotype-dependent and colony formation can be obtained routinely. In order to identify genes for regenerability, we performed a genetic analysis of the characteristic in the F2 generation of a cross between two accessions selected for high and low regenerability. Regeneration frequencies were obtained from protoplast culture of 248 individual F2 plants after 5, 10, and 15 weeks of culture on regeneration medium. Broad-sense heritability estimate was 0.492 at the early stage and lower (0.046–0.149) at advanced stages. The frequency distribution observed during short-term culture can be explained by two independent loci with duplicate dominant genes controlling regeneration. In long-term culture, one additional dominant gene can confer regeneration; i.e., three independent loci are responsible for regenerability. The results suggest that selection for high regeneration response may be efficient at early stages because of the lower environmental influence on the characteristic, and because fewer genes are involved at this stage than at advanced stages. The control of regenerability by a few dominant genes facilitates incorporation of the trait into breeding material. Molecular markers linked to the genes may assist in the selection of genotypes with high regeneration percentage in the future.

Geographical patterns of diversity for morphological and agronomic traits in the groundnut germplasm collection

The characterization of diversity in germplasm collection is important toplant breeders to utilize and to the genebank curators to manage the collection efficiently and effectively. The objective of our study was to describe the phenotypic diversity in the 13342 accessions of groundnut(Arachis hypogaea L.) germplasm contained in the ICRISAT genebank. The germplasm accessions were characteized for 16morphological descriptors, 10 agronomic traits in two seasons, and for reaction to early leaf spot and groundut rosette virus disease, to determine the phenotypic variation in different geographical regions. The phenotypic variation was found for most traits in all the regions. The means for different agronomic traits differed significantly among regions. The variances for all the traits among regions were heterogeneous. South America which showed 100% range variation for 12 of the 16 morphological descriptors and on average showed highest range variation. The Shannon-Weaver diversity index was variable in different regions for different traits. South America among regions, primary seed colour among morphological traits,and leaflet length among agronomic traits showed highest pooled diversity index. Three of the six botanical varieties, aequatoriana, hirsuta,and peruviana were poorly represented and need to be collected. Principal component analysis (PCA) using 38 traits and clustering on first seven PC scores delineated three regional clusters; consisting North America, Middle East, and East Asia in the first cluster, South America in the second cluster, and West Africa, Europe, Central Africa, South Asia,Oceania, Southern Africa, Eastern Africa, Southeast Asia, Central Asia, and Caribbean in the third cluster.

Diversity in Nordic spring wheat cultivars (1901–93)

Nordic plant breeders have selected superior genotypes and released new spring wheat cultivars throughout this century. However, the extent of phenotypic diversity that exists in this improved germplasm has not been accurately investigated. This study phenotypically assessed 75 selected cultivars released to farmers in Denmark, Finland, Norway and Sweden within the last 10 decades. Grouping of cultivars was not related to their geographical origin or decade of release. The respective within‐cluster variances were always larger than the among‐cluster variances. The average phenotypic diversity for Nordic spring wheat germplasm was 0.22, which was not surprising because some newer cultivars were derived from older cultivars. There was a significant influence of geographical origin on days to heading, straw, grain and biomass weight, and kernel number. Likewise, the country × decade of release interaction was significant for all characteristics except plant height. These findings suggest that irrespective of...

Development and deployment of transgenic plants: Biosafety considerations

SummaryRecombinant DNA technology has great potential to enhance and extend the advantages of conventional plant breeding, and increase the production and productivity of crops to meet the increasing demand for food and food products in the future. Judicious application of this technology provides opportunities for alleviating some of the major constraints to crop productivity under subsistence farming conditions in the developing countries. Considerable progress has been made in developing strategies for the production and deployment of transgenic crops. However, biosafety concerns have been raised regarding the deployment and release of genetically engineered plants. This debate has divided the farming and consumer communities over acceptability of genetically modified foods. There is a need for a thorough investigation regarding the fate of transgenic plants in the environment, and their interaction with wild relatives and non-target organisms. The production and release of transgenic plants should be based on experience and sound scientific reasoning. The regulatory requirements for deployment of transgenic crops should be streamlined and harmonized, in order to achieve sustainable food production, poverty reduction, and environmental protection in resource-poor countries in the semi-arid tropics.

Breeding gains and changes in morphotype of Nordic spring wheat (1901–1993) under contrasting environments

Phenotypic diversity among 75 Nordic spring wheat cultivars was assessed in a glasshouse experiment, in which plots had no fertilizer or received 14-3-23 NPK plus Mg. On average, the fertilizer application delayed flowering by one day, shortened plant height (PH), as well as enhanced the number of fertile tillers (NFT), fresh and dry straw weight (FSW and DSW, respectively), but influenced negatively the dry matter content in the straw (DMCS) and the number of kernels per spike (K/S). The cultivar-by-fertilizer interaction did not affect significantly days to flowering (DF), PH, FSW, DSW, DMCS, thousand kernel weight, and K/S. Only NFT was significantly affected by this interaction. There were significant differences among cultivars for all characteristics, and the breeding gains were significant for improving earliness (as determined by DF), shortening PH, as well as for reducing DSW and DMCS irrespective of the environment. On average, FSW was low in newer cultivars grown in high inputs, while NFT was low in newer cultivars when grown in low inputs. The country of origin affected significantly DF, PH, DMCS, K/S, and 1000-kernel weight. On average, cultivars developed for Finland and Norway were significantly taller, and had higher DMCS. Finnish cultivars also flowered 1 or 2 days earlier and showed higher K/S than cultivars adopted in southern Scandinavia or Norway.

Effect of genotype and environment on vegetative and reproductive characteristics of lingonberry (Vaccinium vitis‐idaea L.)

A field experiment was carried out using cuttings and seedlings from 11 selected clones of lingonberry (Vaccinium vitis‐idaea L.) planted at Balsgard, Sweden, in 1982. Daughter plants from two different clones and their corresponding seedling progenies were transferred to a Biothron at Alnarp, Sweden, in 1988. These two clones and their respective seedling populations were cultivated under conditions of controlled temperature and humidity, but in distinct environments with direct light and shade. Data on vegetative and reproductive growth were recorded. A small additional experiment to verify the effects of light on development was performed in frames at Alnarp. The results suggest that the genotype of wild lingonberry accessions controls their spreading ability (i.e. number of rhizomes), influences its growth, thereby affecting plant height, and determines the number of vegetative shoots, total number of shoots and berry set. Furthermore, light influences plant height, vegetative shoots and number of fer...