Cyanogenesis in the Sorghum Genus: From Genotype to Phenotype

Domestication has resulted in a loss of genetic diversity in our major food crops, leading to susceptibility to biotic and abiotic stresses linked with climate change. Crop wild relatives (CWR) may provide a source of novel genes potentially important for re-gaining climate resilience. Sorghum bicolor is an important cereal crop with wild relatives that are endemic to Australia. Sorghum bicolor is cyanogenic, but the cyanogenic status of wild Sorghum species is not well known. In this study, leaves of wild species endemic in Australia are screened for the presence of the cyanogenic glucoside dhurrin. The direct measurement of dhurrin content and the potential for dhurrin-derived HCN release (HCNp) showed that all the tested Australian wild species were essentially phenotypically acyanogenic. The unexpected low dhurrin content may reflect the variable and generally nutrient-poor environments in which they are growing in nature. Genome sequencing of six CWR and PCR amplification of the CYP79A1 gene from additional species showed that a high conservation of key amino acids is required for correct protein function and dhurrin synthesis, pointing to the transcriptional regulation of the cyanogenic phenotype in wild sorghum as previously shown in elite sorghum.

Evolutionary Genetics of Crop-Wild Complexes

Since Darwin’s time, the role of crop wild relatives (CWR), landraces, and cultivated genepools in shaping plant diversity and boosting food resources has been a major question [...]

The grain quality of wheat wild relatives in the evolutionary context

Key message We evaluated the potential of wheat wild relatives for the improvement in grain quality characteristics including micronutrients (Fe, Zn) and gluten and identified diploid wheats and the timopheevii lineage as the most promising resources. Abstract Domestication enabled the advancement of civilization through modification of plants according to human requirements. Continuous selection and cultivation of domesticated plants induced genetic bottlenecks. However, ancient diversity has been conserved in crop wild relatives. Wheat (Triticum aestivum L.; Triticum durum Desf.) is one of the most important staple foods and was among the first domesticated crop species. Its evolutionary diversity includes diploid, tetraploid and hexaploid species from the Triticum and Aegilops taxa and different genomes, generating an AA, BBAA/GGAA and BBAADD/GGAAAmAm genepool, respectively. Breeding and improvement in wheat altered its grain quality. In this review, we identified evolutionary patterns and the potential of wheat wild relatives for quality improvement regarding the micronutrients Iron (Fe) and Zinc (Zn), the gluten storage proteins α-gliadins and high molecular weight glutenin subunits (HMW-GS), and the secondary metabolite phenolics. Generally, the timopheevii lineage has been neglected to date regarding grain quality studies. Thus, the timopheevii lineage should be subject to grain quality research to explore the full diversity of the wheat gene pool.

Auxin-driven ecophysiological diversification of leaves in domesticated tomato

The study of crop diversification has focussed mainly on the genetic changes underlying traits favoured by humans. However, the passage from natural habitats to agronomic settings probably operated changes beyond those comprising the classical domestication syndrome. A deeper understanding of these traits and their genetic signature would be valuable to inform conventional crop breeding and de novo domestication of crop wild relatives. Heterobaric leaves have bundle sheath extensions (BSEs) that compartmentalise the sub-stomatal cavity whereas homobaric leaves do not; BSE development is known to be controlled by the OBSCURAVENOSA (OBV) locus and the obv mutant lacks BSEs whereas leaves carrying the wild type allele have BSEs. Here we identify a non-synonymous amino acid change in the OBV gene that exists as a rare balanced polymorphism in the natural range of wild tomatoes, but has increased in frequency in domesticated tomatoes, suggesting that the latter diversified into heterobaric and homobaric leaf types. The mutation disrupts a C2H2 zinc finger motif in the OBV protein, resulting in the absence of BSEs in leaves and here we show that this and other pleiotropic effects, including changes in leaf insertion angle, leaf margin serration, minor vein density and fruit shape, are controlled by OBV via changes in auxin signalling. Loss of function of the transcriptional regulator AUXIN RESPONSE FACTOR (ARF4) also results in defective BSE development, revealing an additional component of a novel genetic module controlling aspects of leaf development important for ecological adaptation and subject to breeding selections.

Climate Change, Crop Wild Relatives and Genomic Data: The persistence and agronomic utility of five Vitis species

Crop wild relatives (CWRs) have the capacity to contribute novel traits to agriculture. Given climate change, these contributions may be especially vital for perennial crops, because perennials are often clonally propagated and consequently do not evolve rapidly. By studying the landscape genomics of five Vitis CWRs (V. arizonica, V. mustangensis, V. riparia, V. berlandieri and V. girdiana) in the context of projected climate change, we addressed two goals. The first was assessing the relative potential of different CWRs to persist in the context of climate change. By integrating species distribution models with adaptive genetic variation, additional genetic features such as genomic load, and a phenotype (resistance to Pierce Disease), we predicted that accessions of V. mustangensis are particularly well-suited to persist. The second goal was identifying candidate CWRs to contribute to bioclimatic adaptation for grapevine (V. vinifera) cultivation. To do so, we first estimated that ~40% of current viticulture sites in the United States will be vulnerable to climate change, based on species distribution models projected to 2070. We then predicted which CWRs have the genomic profile to contribute to bioclimatic adaptation at these vulnerable sites. We identified rootstock candidates from V. mustangensis, V. riparia and V. girdiana and hypothesized that they may prove useful for mitigating climate impacts on viticulture. By identifying candidate germplasm, this work takes a conceptual step toward mitigating the climate impacts on crops by utilizing the genomic and bioclimatic characteristics of CWRs.

West African Crop Wild Relative Checklist, Prioritization and Inventory

Crop wild relatives (CWR) are wild plant taxa genetically related to domesticated crops with trait diversity that can be used in plant breeding to sustain food security. Prioritization is a prerequisite for the cost–effective conservation of CWR as it allows CWR in a checklist to be reduced to a manageable number for active conservation action. In this study, a partial CWR checklist comprising 1651 taxa was compiled for West Africa. Prioritization of the annotated CWR checklist was based on three criteria: (i) economic value of the related crop in West Africa, (ii) CWR genetic closeness to its related crop and (iii) threat status. After applying the three criteria using the parallel method of prioritization, 102 priority CWR were selected for active conservation action. The priority CWR are related to food crops that are nationally, regionally and globally important, such as white guinea yam (Dioscorea cayenensis subsp. rotundata (Poir) J. Miège), cassava (Manihot esculenta Crantz), rice (Oryza sativa L.), wheat (Triticum aestivum L.), cowpea (Vigna unguiculata (L.) Walp.), sweet potato (Ipomea batatas (L.) Lam.), common bean (Phaseolus vulgaris L.) and sorghum (Sorghum bicolor (L.) Moench). This CWR checklist and prioritization will help in the development of a regional conservation action plan for West Africa.

Crop Wild Relatives Crosses: Multi-Location Assessment in Durum Wheat, Barley, and Lentil

Crop wild relatives (CWR) are a good source of useful alleles for climate change adaptation. Here, 19 durum wheat, 24 barley, and 24 lentil elites incorporating CWR in their pedigrees were yield tested against commercial checks across 19 environments located in Morocco, Ethiopia, Lebanon, and Senegal. For each crop, the combined analysis of variance showed that genotype (G), environment (E), and genotype x environment (GxE) effects were significant for most of the traits. A selection index combining yield potential (G) and yield stability (GxE) was used to identify six CWR-derived elites for each crop matching or superior to the best check. A regression analysis using a climate matrix revealed that grain yield was mostly influenced by the maximum daily temperature and soil moisture level during the growing stages. These climatic factors were used to define five clusters (i.e., E1 to E5) of mega-environments. The CWR-derived elites significantly outperformed the checks in E1, E2, and E4 for durum wheat, and in E2 for both barley and lentil. The germplasm was also assessed for several food transformation characteristics. For durum wheat, one accession (Zeina) originating from T. araraticum was significantly superior in mixograph score to the best check, and three accessions originating from T. araraticum and T. urartu were superior for Zn concentration. For barley, 21 accessions originating from H. spontaneum were superior to the checks for protein content, six for Zn content, and eight for β-glucan. For lentil, ten accessions originating from Lens orientalis were superior to the check for protein content, five for Zn, and ten for Fe concentration. Hence, the results presented here strongly support the use of CWR in breeding programs of these three dryland crops, both for adaptation to climatic stresses and for value addition for food transformation.

Genetic Identity, Diversity, and Population Structure of the Sweetpotato's (I. batatas) Germplasm Collection From International Potato Center's

The in trust sweetpotato collection housed by the International Center of Potato (CIP) is one of the largest assemblages of plant material representing the genetic resources of this important staple crop. The collection currently contains almost 6,000 accessions of Ipomoea batatas (cultivated sweetpotato) and over 1,000 accessions of sweetpotato crop wild relatives (CWRs). In this study, the entire cultivated collection (5,979 accessions) was genotyped with a panel of 20 simple sequence repeat (SSR) markers to assess genetic identity, diversity, and population structure. Genotyping and phenotyping of in vitro plantlets and mother plants were conducted simultaneously on 2,711 accessions (45% of the total collection) to identify and correct possible genetic identity errors which could have occurred at any time over the thirty plus years of maintenance in the in vitro collection. Within this group, 533 accessions (19.6%) had errors in identity. Field evaluations of morphological descriptors were carried out to confirm the marker data. A phylogenetic tree was constructed to reveal the intraspecific relationships in the population which uncovered high levels of redundancy in material from Peru and Latin America. These genotypic data were supported by morphological data. Population structure analysis demonstrated support for four ancestral populations with many of the accessions having lower levels of gene flow from the other populations. This was especially true of germplasm derived from Peru, Ecuador, and Africa. The set of 20 SSR markers was subsequently utilized to examine a subset of 189 accessions from the USDA sweetpotato germplasm collection and to identify and reconcile potential errors in the identification of clones shared between these collections. Marker analysis demonstrated that the USDA subset of material had 65 unique accessions that were not found in the larger CIP collection. As far as the authors are aware, this is the first report of genotyping an entire sweetpotato germplasm collection in its entirety.