Paula J. Bramel

Agriculture: Feeding the future

Humanity depends on fewer than a dozen of the approximately 300,000 species of flowering plants for 80% of its caloric intake. And we capitalize on only a fraction of the genetic diversity that resides within each of these species. This is not enough to support our food system in the future. Food availability must double in the next 25 years to keep pace with population and income growth around the world. Already, food-production systems are precarious in the face of intensifying demand, climate change, soil degradation and water and land shortages. Farmers have saved the seeds of hundreds of crop species and hundreds of thousands of ‘primitive’ varieties (local domesticates called landraces), as well as the wild relatives of crop species and modern varieties no longer in use. These are stored in more than 1,700 gene banks worldwide. Maintaining the 11 international gene-bank collections alone costs about US

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

18 million a year.

Establishment of a pearl millet [Pennisetum glaucum (L.) R.Br.] core collection based on geographical distribution and quantitative traits

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.

Phenotypic diversity for morphological and agronomic characteristics in chickpea core collection

ICRISAT conserves a large collection of pearl millet [Pennisetum glaucum L. R. (Br.)] comprising of 21,392 accessions. This includes landraces, cultivars, genetic stocks, breeding lines, and wild relatives from 50 countries. However, only a small fraction of this huge collection has been exhaustively used in the pearl millet improvement program. The objective of our research was to develop a core collection of pearl millet to enhance utilization of genetic resources in improvement programs and simplify their management. For this purpose, accessions were initially stratified according to geographical distribution followed by hierarchical clustering on 11 quantitative traits using Ward’s method. This resulted in 25 distinct groups. Approximately 10% accessions were then randomly selected from each of these 25 distinct groups to form a core collection of 1,600 accessions. Different statistical methods like comparison of mean using Newman–Keuls test, variance using Levene’s test, frequency distributions using Chi-square test, and Wilcoxon’s rank-sum non-parametric test for the traits validated that the variation present in entire collection had been preserved in the core collection. The important phenotypic correlations among different traits that may be under the control of co-adapted gene complexes were also preserved in the core collection. The diversity represented in the core collection will therefore, be a guideline to breeders for a wider use of the pearl millet genetic resources available in the genebank.

Sorghums of the sudan: analysis of regional diversity and distribution

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.

Assessment of genetic diversity within and between pearl millet landraces

Sorghum [Sorghumbicolor (L.) Moench] is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums.

The Need to Look Beyond the Production and Provision of Relief Seed: Experiences from Southern Sudan

Abstract.A minimum core subset of pearl millet [Pennisetum glaucum (L.) R. Br.], which comprised 504 landrace accessions, was recently established from the global pearl millet germplasm collection of ICRISAT. The accessions for this core were selected by a random proportional sampling strategy following stratification of the entire landrace collection (about 16,000 accessions) according to their geographic origin and morpho-agronomic traits. In this study RFLP probes were used to quantify the genetic diversity within and between landrace accessions of this minimum core using a subset comprising ten accessions of Indian origin. Twenty five plants per accession were assayed with EcoRI, EcoRV, HindIII and DraI restriction enzymes, and 16 highly polymorphic RFLP probes, nine associated with a quantitative trait loci (QTLs) for downy mildew resistance, and five associated with a QTL for drought tolerance. A total of 51 alleles were detected using 16 different probe-enzyme combinations. The partitioning of variance components based on the analysis of molecular variance (AMOVA) for diversity analysis revealed high within-accession variability (30.9%), but the variability between accessions was significantly higher (69.1%) than that within the accessions. A dendrogram based on the dissimilarity matrix obtained using Wards algorithm further delineated the 250 plants into ten major clusters, each comprised of plants from a single accession (with the exception of two single plants). A similar result was found in an earlier study using morpho-agronomic traits and geographic origin. This study demonstrated the utility of RFLP markers in detecting polymorphism and estimating genetic diversity in a highly cross-pollinated species such as pearl millet. When less-tedious marker systems are available, this method could be further extended to assess the genetic diversity between and within the remaining accessions in the pearl millet core subset.

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

Free distribution of seeds in selected areas of southern Sudan has been widespread as a way of increasing food security. Field research in areas targeted for seed relief found that farmer seed systems continue to meet the crop and varietal needs of farmers even following the 1998 famine. Donor investments in seed multiplication of improved sorghum have not been sustained due to a lack of effective demand for the improved seed beyond that created by the relief agencies. The article argues that rather than imposing outside solutions, whether through seed provisioning or seed production enterprises, greater attention needs to be given to building on the strengths of existing farmer systems and designing interventions to alleviate the weaknesses. The case is made to support dynamically the process of farmer experimentation through the informed introduction of new crops and varieties that can potentially reinforce the strength and diversity of local cropping systems.

Biogeography of wild Arachis (Leguminosae):distribution and environmental characterisation

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.

Efficiency of three DNA markers in revealing genetic variation among wild Cajanus species.

Geographic Information System (GIS) tools are applied to a comprehensive database of 3514 records of wild Arachis species to assist in the conservation and utilisation of the species by: (a) determining the distributional range of species and their abundance; (b) characterising species environments; (c) determining the geographical distribution of species richness; and (d) determining the extent to which species are associated with river basins. Distributional ranges, climatic variables and indices of endemism for each species are tabulated. A. duranensis Krapov. & W.C. Gregory, the most probable donor of the A genome to the cultivated peanut, is distributed in close proximity to both the proposed donor of the B genome, A. ipaënsis, and the closest wild relative of the cultigen, A. monticola Krapov. & Rigoni. This region in the eastern foothills of the Andes and the adjoining chaco regions of Argentina, Bolivia and Paraguay, is a key area for further exploration for wild Arachis. An area of particularly high species richness occurs in the State of Mato Grosso, close to the Gran Pantanal in southwest Brazil. Seventy-one percent of the species were found to have some degree of association with water catchment areas, although in most cases it was difficult to determine whether this was due to climatic adaptation reasons, restricted dispersal due to geocarpic habit, or the role of watercourses as a principal dispersal agent. In only two cases could climatic adaptation be eliminated as the reason for species distribution.