Leaf morphology in cowpea [Vigna unguiculata (L.) Walp]: QTL analysis, physical mapping and identifying a candidate gene using synteny with model legume species

Cowpea [Vigna unguiculata (L.) Walp] exhibits a considerable variation in leaf shape. Although cowpea is mostly utilized as a dry grain and animal fodder crop, cowpea leaves are also used as a high-protein pot herb in many countries of Africa

There and back again: historical perspective and future directions for Vaccinium breeding and research studies

The genus Vaccinium L. (Ericaceae) contains a wide diversity of culturally and economically important berry crop species. Consumer demand and scientific research in blueberry (Vaccinium spp.) and cranberry (Vaccinium macrocarpon) have increased worldwide over the crops' relatively short domestication history (~100 years). Other species, including bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), and ohelo berry (Vaccinium reticulatum) are largely still harvested from the wild but with crop improvement efforts underway. Here, we present a review article on these Vaccinium berry crops on topics that span taxonomy to genetics and genomics to breeding. We highlight the accomplishments made thus far for each of these crops, along their journey from the wild, and propose research areas and questions that will require investments by the community over the coming decades to guide future crop improvement efforts. New tools and resources are needed to underpin the development of superior cultivars that are not only more resilient to various environmental stresses and higher yielding, but also produce fruit that continue to meet a variety of consumer preferences, including fruit quality and health related trait

Genomics-assisted breeding in four major pulse crops of developing countries: present status and prospects

The global population is continuously increasing and is expected to reach nine billion by 2050. This huge population pressure will lead to severe shortage of food, natural resources and arable land. Such an alarming situation is most likely to arise in developing countries due to increase in the proportion of people suffering from protein and micronutrient malnutrition. Pulses being a primary and affordable source of proteins and minerals play a key role in alleviating the protein calorie malnutrition, micronutrient deficiencies and other undernourishment-related issues. Additionally, pulses are a vital source of livelihood generation for millions of resource-poor farmers practising agriculture in the semi-arid and sub-tropical regions. Limited success achieved through conventional breeding so far in most of the pulse crops will not be enough to feed the ever increasing population. In this context, genomics-assisted breeding (GAB) holds promise in enhancing the genetic gains. Though pulses have long been considered as orphan crops, recent advances in the area of pulse genomics are noteworthy, e.g. discovery of genome-wide genetic markers, high-throughput genotyping and sequencing platforms, high-density genetic linkage/QTL maps and, more importantly, the availability of whole-genome sequence. With genome sequence in hand, there is a great scope to apply genome-wide methods for trait mapping using association studies and to choose desirable genotypes via genomic selection. It is anticipated that GAB will speed up the progress of genetic improvement of pulses, leading to the rapid development of cultivars with higher yield, enhanced stress tolerance and wider adaptability

A Model of Spring Break Travel among University Students

This study tested a model to predict the likelihood of spring break travel among university students. The data were obtained from a 1996 survey sample of 303 university students

Modern approaches for cowpea breeding: how highthroughput genotyping and a highdensity map change everything

The genomics revolution has enabled rapid advances in genotyping capabilities and construction of high-density genetic linkage maps that enable new plant breeding strategies which have the potential to expedite delivery of improved crop varieties. These breeding strategies utilize molecular marker information at hundreds to thousands of points in the genome, encompassing selection for multiple traits and/or multigenic traits. This chapter summarizes the opportunities and challenges for the cowpea breeding community in adopting modern breeding given the recent development of enabling genomic resources. These resources include high-throughput SNP genotyping platforms, high-density consensus genetic map with more than 1000 markers, and QTL(s) linked to important biotic and abiotic resistance traits, including resistance to foliar and flower thrips, Fusarium wilt, root-knot nematode, bacterial blight, ashy stem blight (Macrophomina), Striga, and components of drought tolerance. Initial work in evaluating and optimizing marker-assisted backcross (MABC), marker-assisted pedigree breeding (MAPB), and marker-assisted recurrent selection (MARS) in cowpea breeding is described. We also report on the successful completion of tests evaluating the feasibility of outsourced SNP genotyping by African NARS breeders. Cost of genotyping, while much reduced compared to the recent past, is still a major constraint to widespread adoption of modern breeding by developing country NARS. High throughput precision phenotyping methods are needed to properly complement the recent advances in genomic resources. New resources and tools to help overcome these challenges have recently become available to breeders within the cowpea community, particularly in the areas of improving information management capability, decision making tools for marker-assisted breeding, and experimental design for precision phenotyping. Comprehensive training of breeders in the use of these tools is urgently needed

Modern approaches for cowpea breeding

The genomics revolution has enabled rapid advances in genotyping capabilities and construction of high-density genetic linkage maps that enable new plant breeding strategies which have the potential to expedite delivery of improved crop varieties. These breeding strategies utilize molecular marker information at hundreds to thousands of points in the genome, encompassing selection for multiple traits and/or multigenic traits. This chapter summarizes the opportunities and challenges for the cowpea breeding community in adopting modern breeding given the recent development of enabling genomic resources. These resources include high-throughput SNP genotyping platforms, high-density consensus genetic map with more than 1000 markers, and QTL(s) linked to important biotic and abiotic resistance traits, including resistance to foliar and flower thrips, Fusarium wilt, root-knot nematode, bacterial blight, ashy stem blight (Macrophomina), Striga, and components of drought tolerance. Initial work in evaluating and optimizing marker-assisted backcross (MABC), marker-assisted pedigree breeding (MAPB), and marker-assisted recurrent selection (MARS) in cowpea breeding is described. We also report on the successful completion of tests evaluating the feasibility of outsourced SNP genotyping by African NARS breeders. Cost of genotyping, while much reduced compared to the recent past, is still a major constraint to widespread adoption of modern breeding by developing country NARS. High throughput precision phenotyping methods are needed to properly complement the recent advances in genomic resources. New resources and tools to help overcome these challenges have recently become available to breeders within the cowpea community, particularly in the areas of improving information management capability, decision making tools for marker-assisted breeding, and experimental design for precision phenotyping. Comprehensive training of breeders in the use of these tools is urgently needed

TREE CANOPY RESEARCH AND STUDENT EXPERIENCES USING THE DOUBLED ROPE CLIMBING METHOD

Volume: 2Start Page: 1309End Page: 133

Genomics-assisted breeding for drought tolerance in cowpea

Published online: 02 July 2019The importance of cowpea, Vigna unguiculata, in human and animal nutrition and sustainability of soil fertility are recognized globally especially in sub-Saharan Africa (SSA) where the crop is mainly produced in the Savanna and the Sahelian agro ecologies. However, cowpea productivity is adversely affected by both biotic (insect pests, diseases, parasitic weeds, nematodes) and abiotic (drought, heat, low soil fertility) constraints. Appreciable progress has been made in the improvement of cowpea for resistance to some biotic stresses particularly diseases such as bacterial blight, ashy stem blight, marcophomina, parasitic weeds like Striga and Alectra and some insects like aphid, leaf and flower thrips among others. There is need for intensifying research activities with focus on improving cowpea resistance to abiotic stresses. As a crop grown commonly in arid regions, cowpea is subjected to seedling stage, midseason and terminal droughts. In the recent past, the amount of rainfall, during the cropping season in the dry savannah regions of SSA, is getting less. Consequently the cropping season is getting shorter occasioned by late commencement or early cessation of the rain. Farmers in the cowpea producing areas of SSA generally have no access to irrigation hence their crops are grown under rain-fed conditions. With the impending higher frequency of drought in the dry savannah region due to climate change, efforts should be made in developing climate resilient cowpea varieties that farmers will grow. Efforts have been made in enhancing tolerance to drought in some improved cowpea varieties using conventional breeding but progress has been slow in this regard. Drought tolerance is a complex trait and many genes are involved in its inheritance. Pyramiding of these genes in improved varieties would therefore, be desirable. Such varieties with pyramided genes are likely to be stable in performance over the years and across several locations in the savannahs. Recent developments in molecular biology could play significant role in the development of such resilient varieties. In a number of crops, molecular markers associated with resistance loci have been identified and are being used in marker assisted breeding. Marker assisted backcrossing (MABC) is the choice when single traits that are simply inherited are to be moved to varieties with superior performance but lacking in the trait being transferred. Also, marker assisted recurrent selection (MARS) has shown promise in accumulating multiple genes in improved varieties of some crops. Some work has been initiated in cowpea on the use of MARS to pyramid resistance to Striga, yield and drought. Results obtained so far show the potential of this method in pyramiding desirable genes in cowpea. As more resources get committed to cowpea research a solid foundation would be established for the generation of molecular tools that should facilitate their routine application to the improvement of the crop

A consensus genetic map of cowpea [Vigna unguiculata (L) Walp.] and synteny based on EST-derived SNPs

Consensus genetic linkage maps provide a genomic framework for quantitative trait loci identification, map-based cloning, assessment of genetic diversity, association mapping, and applied breeding in marker-assisted selection schemes. Among “orphan crops” with limited genomic resources such as cowpea [Vigna unguiculata (L.) Walp.] (2n = 2x = 22), the use of transcript-derived SNPs in genetic maps provides opportunities for automated genotyping and estimation of genome structure based on synteny analysis. Here, we report the development and validation of a high-throughput EST-derived SNP assay for cowpea, its application in consensus map building, and determination of synteny to reference genomes. SNP mining from 183,118 ESTs sequenced from 17 cDNA libraries yielded ≈10,000 high-confidence SNPs from which an Illumina 1,536-SNP GoldenGate genotyping array was developed and applied to 741 recombinant inbred lines from six mapping populations. Approximately 90% of the SNPs were technically successful, providing 1,375 dependable markers. Of these, 928 were incorporated into a consensus genetic map spanning 680 cM with 11 linkage groups and an average marker distance of 0.73 cM. Comparison of this cowpea genetic map to reference legumes, soybean (Glycine max) and Medicago truncatula, revealed extensive macrosynteny encompassing 85 and 82%, respectively, of the cowpea map. Regions of soybean genome duplication were evident relative to the simpler diploid cowpea. Comparison with Arabidopsis revealed extensive genomic rearrangement with some conserved microsynteny. These results support evolutionary closeness between cowpea and soybean and identify regions for synteny-based functional genomics studies in legumes

A major QTL corresponding to the Rk locus for resistance to root-knot nematodes in cowpea (Vigna unguiculata L. Walp.)

KEY MESSAGE: Genome resolution of a major QTL associated with theRklocus in cowpea for resistance to root-knot nematodes has significance for plant breeding programs and R gene characterization. ABSTRACT: Cowpea (Vigna unguiculata L. Walp.) is a susceptible host of root-knot nematodes (Meloidogyne spp.) (RKN), major plant-parasitic pests in global agriculture. To date, breeding for host resistance in cowpea has relied on phenotypic selection which requires time-consuming and expensive controlled infection assays. To facilitate marker-based selection, we aimed to identify and map quantitative trait loci (QTL) conferring the resistance trait. One recombinant inbred line (RIL) and two F2:3 populations, each derived from a cross between a susceptible and a resistant parent, were genotyped with genome-wide single nucleotide polymorphism (SNP) markers. The populations were screened in the field for root-galling symptoms and/or under growth-chamber conditions for nematode reproduction levels using M. incognita and M. javanica biotypes. One major QTL was mapped consistently on linkage group VuLG11 of each population. By genotyping additional cowpea lines and near-isogenic lines derived from conventional backcrossing, we confirmed that the detected QTL co-localized with the genome region associated with the Rk locus for RKN resistance that has been used in conventional breeding for many decades. This chromosomal location defined with flanking markers will be a valuable target in marker-assisted breeding and for positional cloning of genes controlling RKN resistance. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-015-2611-0) contains supplementary material, which is available to authorized users