An integrated molecular and conventional breeding scheme for enhancing genetic gain in maize in Africa

Open Access Journal; Published online: 06 Nov 2019Maize production in West and Central Africa (WCA) is constrained by a wide range of interacting stresses that keep productivity below potential yields. Among the many problems afflicting maize production in WCA, drought, foliar diseases, and parasitic weeds are the most critical. Several decades of efforts devoted to the genetic improvement of maize have resulted in remarkable genetic gain, leading to increased yields of maize on farmers’ fields. The revolution unfolding in the areas of genomics, bioinformatics, and phenomics is generating innovative tools, resources, and technologies for transforming crop breeding programs. It is envisaged that such tools will be integrated within maize breeding programs, thereby advancing these programs and addressing current and future challenges. Accordingly, the maize improvement program within International Institute of Tropical Agriculture (IITA) is undergoing a process of modernization through the introduction of innovative tools and new schemes that are expected to enhance genetic gains and impact on smallholder farmers in the region. Genomic tools enable genetic dissections of complex traits and promote an understanding of the physiological basis of key agronomic and nutritional quality traits. Marker-aided selection and genome-wide selection schemes are being implemented to accelerate genetic gain relating to yield, resilience, and nutritional quality. Therefore, strategies that effectively combine genotypic information with data from field phenotyping and laboratory-based analysis are currently being optimized. Molecular breeding, guided by methodically defined product profiles tailored to different agroecological zones and conditions of climate change, supported by state-of-the-art decision-making tools, is pivotal for the advancement of modern, genomics-aided maize improvement programs. Accelerated genetic gain, in turn, catalyzes a faster variety replacement rate. It is critical to forge and strengthen partnerships for enhancing the impacts of breeding products on farmers’ livelihood. IITA has well-established channels for delivering its research products/technologies to partner organizations for further testing, multiplication, and dissemination across various countries within the subregion. Capacity building of national agricultural research system (NARS) will facilitate the smooth transfer of technologies and best practices from IITA and its partners

Screening of Soybean Germplasm Collection Resistance to Rust Disease (Phakopsora Pachyrhizi)

Rust disease is an important disease on soybean, it was widely distributed in almost all soybeanproducing countries, the yield losses can be reach 85 %. One of the control measured is planting theresistant varieties. Resistant gens of one character can be obtained from the germplasm collection. Thestudy aiar to evaluate the resistance of soybean germplasm collection against rust diseases. The study wasconducted at Kendalpayak experimental station, Indonesian Legumes and Tuber Crops ResearchInstitute, in June to September 2013. Materials used were 175 genotypes of soybean germplasm collection.Observations of rust disease resistance based on the method of International Working Group on SoybeanRust system. The results showed that out of 175 soybean genotypes tested, 162 genotypes were moderatelyresistant, 12 genotypes were moderately susceptible , and one genotype was susceptible to rust disease

Impact of ICARDA Research on Australian Agriculture

Research and Development/Tech Change/Emerging Technologies,

Use of genetic resources and partial resistances for apple breeding

Modern apple breeding strategies are mainly considering the most advanced selections and culti-vars as parents. This tends to lead to a narrowed genetic basis. The introgression of traditional va-rieties and accessions of the gene pool is often feared due to undesirable characteristics that might be incorporated. However, there is scope for considering a wider genetic basis in apple breeding to support sustainable fruit production systems. The focus at Agroscope Changins-Wädenswil (ACW) is put on high fruit quality combined with low susceptibility to scab (Venturia inaequalis), fire blight (Erwinia amylovora), and powdery mildew (Podosphaera leucotricha). The Swiss scab and fire blight resistance research programs are focused on developing and applying molecular markers for resistance factors. In this context we are also mining our national germplasm collections of heritage varieties. Heritage varieties are traditional and/or special use apple varieties. Many of them were discovered in the course of a national inventory over the past 5 years. As a result of this inventory, 1’100 apple and 670 pear accession are being added into the germplasm collections. They will be evaluated in the coming years for different fruit and tree characters

Combating stem and leaf rust of wheat: Historical perspective, impacts, and lessons learned

millions fed, food security, wheat rust, stem rust, leaf rust, Norman Borlaug,

Genetic diversity of peanut (Arachis hypogaea L.) and its wild relatives based on the analysis of hypervariable regions of the genome

BACKGROUND: The genus Arachis is native to a region that includes Central Brazil and neighboring countries. Little is known about the genetic variability of the Brazilian cultivated peanut (Arachis hypogaea, genome AABB) germplasm collection at the DNA level. The understanding of the genetic diversity of cultivated and wild species of peanut (Arachis spp.) is essential to develop strategies of collection, conservation and use of the germplasm in variety development. The identity of the ancestor progenitor species of cultivated peanut has also been of great interest. Several species have been suggested as putative AA and BB genome donors to allotetraploid A. hypogaea. Microsatellite or SSR (Simple Sequence Repeat) markers are co-dominant, multiallelic, and highly polymorphic genetic markers, appropriate for genetic diversity studies. Microsatellite markers may also, to some extent, support phylogenetic inferences. Here we report the use of a set of microsatellite markers, including newly developed ones, for phylogenetic inferences and the analysis of genetic variation of accessions of A. hypogea and its wild relatives. RESULTS: A total of 67 new microsatellite markers (mainly TTG motif) were developed for Arachis. Only three of these markers, however, were polymorphic in cultivated peanut. These three new markers plus five other markers characterized previously were evaluated for number of alleles per locus and gene diversity using 60 accessions of A. hypogaea. Genetic relationships among these 60 accessions and a sample of 36 wild accessions representative of section Arachis were estimated using allelic variation observed in a selected set of 12 SSR markers. Results showed that the Brazilian peanut germplasm collection has considerable levels of genetic diversity detected by SSR markers. Similarity groups for A. hypogaea accessions were established, which is a useful criteria for selecting parental plants for crop improvement. Microsatellite marker transferability was up to 76% for species of the section Arachis, but only 45% for species from the other eight Arachis sections tested. A new marker (Ah-041) presented a 100% transferability and could be used to classify the peanut accessions in AA and non-AA genome carriers. CONCLUSION: The level of polymorphism observed among accessions of A. hypogaea analyzed with newly developed microsatellite markers was low, corroborating the accumulated data which show that cultivated peanut presents a relatively reduced variation at the DNA level. A selected panel of SSR markers allowed the classification of A. hypogaea accessions into two major groups. The identification of similarity groups will be useful for the selection of parental plants to be used in breeding programs. Marker transferability is relatively high between accessions of section Arachis. The possibility of using microsatellite markers developed for one species in genetic evaluation of other species greatly reduces the cost of the analysis, since the development of microsatellite markers is still expensive and time consuming. The SSR markers developed in this study could be very useful for genetic analysis of wild species of Arachis, including comparative genome mapping, population genetic structure and phylogenetic inferences among species

High-value cassava: From a dream to a concrete reality

Cassava (Manihot esculenta Crantz) is an important food security crop for many tropical and subtropical countries. It is also acquiring an increasing role in rural development as raw material for different industries. The most important industrial uses of cassava are as a source of energy in the feed industry, the bio-ethanol and starch industries, and for processed food. For cassava to be a suitable raw material for different industrial pathways, it has to have a competitive price, which is dependent on high and stable fresh root production, high dry matter content and adequate cultural practices that will maximize yields and reduce production costs. For years many institutions have successfully satisfied these needs. However, to consolidate and expand the industrial uses of cassava, the cassava breeding project at CIAT began increasing the emphasis in the search for value-added traits with the turn of the millennium. Several strategies have been implemented simultaneously. For the feed industry, the main objective is enhanced nutritional quality, particularly with regard to protein and pro-vitamin A carotenoids content. For the starch industry, amylose-free and high-amylose mutations have been identified. Inbreeding has been introduced to cassava genetic improvement because it offers many advantages, including a facilitated identification of useful recessive traits including new plant architecture types. Ongoing research for the production of doubled-haploid lines will reduce the time required to reach full homozygosity. Finally, CIAT has set up a high capacity root-quality laboratory to routinely screen the roots of the thousands of new genotypes generated every year. (Résumé d'auteur

Dispersal of transgenes through maize seed systems in Mexico.

ObjectivesCurrent models of transgene dispersal focus on gene flow via pollen while neglecting seed, a vital vehicle for gene flow in centers of crop origin and diversity. We analyze the dispersal of maize transgenes via seeds in Mexico, the crop's cradle.MethodsWe use immunoassays (ELISA) to screen for the activity of recombinant proteins in a nationwide sample of farmer seed stocks. We estimate critical parameters of seed population dynamics using household survey data and combine these estimates with analytical results to examine presumed sources and mechanisms of dispersal.ResultsRecombinant proteins Cry1Ab/Ac and CP4/EPSPS were found in 3.1% and 1.8% of samples, respectively. They are most abundant in southeast Mexico but also present in the west-central region. Diffusion of seed and grain imported from the United States might explain the frequency and distribution of transgenes in west-central Mexico but not in the southeast.ConclusionsUnderstanding the potential for transgene survival and dispersal should help design methods to regulate the diffusion of germplasm into local seed stocks. Further research is needed on the interactions between formal and informal seed systems and grain markets in centers of crop origin and diversification

Optimal Search in Ex situ Collections of Wheat Genetic Resources

This paper develops a theoretical model for analyzing gene bank management decisions regarding the search for traits of economic value in ex situ collections of wheat. The model is applied to data on the probability of finding useful sources of resistance to Russian wheat aphid (Diuraphis noxia) and septoria tritici leaf blotch, using Monte Carlo simulations for sampling distributions, simulations of varietal diffusion paths, and actual cost data from searches. Three specific questions are posed and answered: (1) what is the optimal size of search among genetic resources of a given type for a trait of economic value? (2) what is the value of specialized knowledge about which genetic resources are most likely to display resistance? and (3) how should search resources be allocated across types of genetic resources? Results demonstrate the sensitivity of the optimal size of search to the economic importance of the problem, the probability distributions of the trait in different types of genetic resources, and the costs and time lags associated with transferring the trait into usable breeding material. The costs and time lags involved with conventional pre-breeding techniques imply that in some searches, certain categories of genetic resources (such as landraces) will be systematically ignored. The fact that they may be rarely utilized does not imply that collections of landraces have no value, however, as shown in the case of Russian wheat aphid. Though applied here to data on insect and disease resistance, the model can be adapted to search decisions for other types of traits.Crop Production/Industries,

Screening natural oil palm (Elaeis guineensis Jacq.) populations using SSR markers

The assessment of genetic diversity and genetic structure of natural oil palm populations is carried out mostly for crop improvement purpose. A set of 16 microsatellite markers was used to genotype 494 palms from 49 populations belonging to ten African countries, three breeding and one semi-wild materials. The number of alleles per locus varied from 8 to 22, making a total of 209 alleles over the 16 microsatellite markers. The effective number varied from 1.1 in all populations from Madagascar to 4.7 in population 40 from Nigeria (mean = 3.30. Mean expected heterozygosity was high (0.644) ranging from 0.033 in population 3 from Madagascar to 0.803 in population 40 from Nigeria. The average genetic distance among oil palm populations was 0.684. An UPGMA cluster analysis showed three main clusters. One cluster grouped accessions from Madagascar while populations from Senegal, Guinea and Sierra Leone formed the second cluster. Populations from Ghana, Nigeria, Cameroon, Zaire, Angola, Tanzania and the breeding materials formed the third cluster. The grouping of Deli MPOB and Deli Dabou breeding materials into the same sub-cluster confirmed their common origin. The results acquired lead to redefining new strategies to make the most of the new genetic resources in oil palm improvement. (Résumé d'auteur