Tertiary Gene Pool Research Articles

Identification and Characterization of Wheat-Aegilops comosa 7M (7A) Disomic Substitution Lines with Stripe Rust and Powdery Mildew Resistance.

Aegilops comosa (MM, 2n = 2x = 14), an important diploid species from the wheat tertiary gene pool, contains many unique genes/traits of potential use for wheat breeding, such as disease resistance. In this study, three sister lines, NAL-32, NAL-33, and NAL-34, were identified from a wheat-A. comosa distant cross using fluorescence in situ hybridization, simple sequence repeat markers, and PCR-based unique gene markers combined with single nucleotide polymorphism (SNP) array analysis. Genetically, NAL-32 contained neither an alien nor translocation chromosome, whereas NAL-33 and NAL-34 had disomic 7M (7A) substitution chromosomes but differed in the absence or presence of the 1BL/1RS translocation chromosomes, respectively. The absence of 7A in NAL-33 and NAL-34 and the unusual 1B in the latter were verified by wheat 55K SNP arrays. The two 7M (7A) substitution lines had similar levels of resistance to stripe rust and powdery mildew, but better than that of NAL-32 and their common wheat parents, suggesting that the stripe rust and powdery mildew resistance of NAL-33 and NAL-34 were derived from the 7M of A.comosa. This research provides important bridge materials that can potentially be used for transferring stripe rust and powdery mildew resistance.

Fully matured F1 Seed Formed in the Cross between Cultivated Chickpea (Cicer arietinum L.) and the Tertiary Gene Pool Species, Cicer pinnatifidum without Embryo Rescue but Albinism Persists

Although pod and seed formation in these interspecific crosses can be improved by involving diverse genotypes in crossing, geneflow between these materials is hindered by a strong genetic factor conferring albinism in the F1 hybrids.

Photoperiod Insensitivity in Pigeonpea Introgression Lines Derived from Wild Cajanus Species

Pigeonpea is a photoperiod-sensitive crop; therefore, the introgression of photoperiod insensitivity could increase its adaptability to new environments. We determined the effect of extended daylength (ED; 16 h light) on the phenotypical traits of extra-early, early, and mid-early maturing pigeonpea introgression lines (ILs) derived from wild Cajanus species belonging to secondary and tertiary gene pools. Plants were grown under natural daylength and extended daylength in a greenhouse. Comparisons of the time of floral bud initiation, days to flowering, plant height, number of branches, and number of leaf nodes on the main stem at flowering revealed photoperiod-insensitive lines. All traits varied widely among the ILs. Analyses of flowering traits revealed large genetic components with low genotype × treatment interactions and high broad-sense heritability. The photoperiod most strongly affected the number of primary branches, followed by plant height. The extended day advanced flowering by approximately four days in extra-early ILs, confirming that these ILs are quantitative, short-day plants. The photoperiod insensitivity index varied from 0.88 in ICPP 171541 (moderately photoperiod sensitive) to 0.99 in ICPP 171546 and ICPP 171561 (photoperiod insensitive). These photoperiod-insensitive extra-early flowering ILs can be used to enrich the genetic diversity of pigeonpea and to develop photoperiod-insensitive cultivars for cultivation in new environments.

Wild rice research: Advancing plant science and food security

Wild rice research: Advancing plant science and food security

Variability in Physiological Traits Reveals Boron Toxicity Tolerance in Aegilops Species.

Boron (B) is an important micronutrient required for the normal growth and development of plants. However, its excess in the soil causes severe damage to plant tissues, which affects the final yield. Wheat, one of the main staple crops, has been reported to be largely affected by B toxicity stress in arid and semi-arid regions of the world. The prevalence of B toxicity stress can be addressed by utilizing wild wheat genotypes with a variant level of stress tolerance. Wild wheat relatives have been identified as a prominent source of several abiotic stress-tolerant genes. However, Aegilops species in the tertiary gene pool of wheat have not been well exploited as a source of B toxicity tolerance. This study explores the root and shoot growth, proline induction, and extent of lipid peroxidation in 19 Aegilops accessions comprising 6 different species and the B-tolerant check wheat cultivar Bolal 2973 grown under Control (3.1 μM B), toxic (1 mM B), and highly toxic (10 mM B) B stress treatment. B toxicity stress had a more decisive impact on growth parameters as compared to the malondialdehyde (MDA) and proline content. The obtained results suggested that even the genotypes with high shoot B (SB) accumulation can be tolerant to B toxicity stress, and the mechanism of B redistribution in leaves should be studied in detail. It has been proposed that the studied Aegilops accessions can be potentially used for genetically improving the B toxicity-tolerance trait due to a high level of variation in the response toward high B toxicity. Though a number of accessions showed suppression in the root and shoot growth, very few accessions with stress adaptive plasticity to B toxicity stress leading to an improvement of shoot growth parameters could be determined. The two accessions, Aegilops biuncialis accession TGB 026219 and Aegilops columnaris accession TGB 000107, were identified as the potential genotypes with B toxicity stress tolerance and can be utilized for developing a pre-breeding material in B tolerance-based breeding programs.

Secondary genepool of Australian Cajanus species contains sources of resistance to Helicoverpa armigera (Hübner)

AbstractA narrow genetic base in cultivated pigeonpea (Cajanus cajan (L.) Millsp.) limits the host plant resistance (HPR) to the devastating pest Helicoverpa armigera (Hübner). Earlier research on pod borer resistance in wild Cajanus relatives has mainly explored the tertiary genepool, making breeding for resistance difficult because of linkage drag. Previous investigations on a wide range of Australian native germplasm from the secondary and tertiary gene pools revealed resistance in the secondary gene pool, associated with total phenolic content (TPC). This study reports the application of the extreme phenotype genome‐wide association (XP‐GWAS) to associate single nucleotide polymorphisms (SNPs) with resistance traits. Mapping of 19 accessions, including 12 wild accessions to a reference pigeonpea genome have identified a total of 16,489 and 16,227 nonsynonymous SNPs for the resistance and TPC traits, respectively. These SNPs were subjected to functional analysis, and KEGG pathway analysis revealed the presence of candidate genes coding for the crucial enzymes in five defence‐related pathways that could be contributing to resistance. These pathways involve ‘Jasmonic acid synthesis’ (palmitoyl‐CoA hydrolase, phospholipase A1 and phospholipase A2), ‘insect hormone biosynthesis’ (aldehyde dehydrogenase) ‘Steroid biosynthesis’ (squalene monooxygenase, farnesyl transferase and lanosterol synthase), ‘Cutin, suberine and wax synthesis’ (O‐acyltransferase) and ‘Brassinosteroid biosynthesis’ (Det2). Analysis of SNPs associated with the TPC trait led to the identification of a divergent pathway of ‘secondary metabolite synthesis’ (flavonoid 3′ hydroxylase, l‐rhamnosyltransferase) in wild Cajanus species consistent with a high concentration of isoorientin and the possible presence of its derivative maysin; a strong insecticidal compound in leaves.

Challenges and Prospects of Wild Soybean as a Resistance Source Against Soybean Aphid (Hemiptera: Aphididae)

AbstractCrop wild relatives (CWRs) have high levels of genetic diversity compared to their domesticated descendants. Soybean (Glycine max) has over 20 species of CWRs, most of which are in secondary and tertiary gene pools. Glycine soja, hereafter ‘soja,’ is the only wild relative in the primary gene pool, i.e., species that readily cross with soybean. Soja has many advantageous traits that may be transferrable to soybean, including resistance to insect pests, with particularly strong sources of resistance to the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). Soybean aphid has been a major soybean pest in the United States and Canada since 2000 and a longstanding pest in East Asia. This paper reviews the challenges of developing soybean with durable resistance to soybean aphid in light of multiple, virulent biotypes in North America and China. It also examines particular challenges in evaluating soja germplasm for soybean aphid resistance and resultant solutions to those challenges. Soja germplasm is widely available, but from our experience, the logistics associated with reliably procuring high-quality soja seed has posed the main challenge in working with this CWR. This review highlights soja accessions identified with strong resistance to soybean aphid and their genetic bases, and it discusses possible strategies for exploiting aphid-resistant soja accessions to improve soybean pest management.

A robust KASP marker for selection of four pairs of linked leaf rust and stripe rust resistance genes introgressed on chromosome arm 5DS from different wheat genomes.

Stripe rust and leaf rust are among the most devastating diseases of wheat, limiting its production globally. Wheat wild relatives harbour genetic diversity for new genes and alleles for all major wheat diseases. However, the use of this genetic variation from wild progenitor and non-progenitor species has been limited in the breeding programs. Reasons include limited recombination of donor and recipient genomes and the lack of tertiary gene pool markers. Here, we describe the development of a SNP based marker from the flow-sorted and sequenced Aegilops umbellulata chromosome 5U which can be used for marker assisted selection of four pair of alien leaf rust and stripe rust resistance genes. Lr57-Yr40_CAPS16 marker was reported earlier to be linked with alien leaf and stripe rust resistance genes introgressed on wheat chromosome 5DS. Due to its dominant nature and laborious to work with, a new SNP-based KASP marker, XTa5DS-2754099_kasp23, was developed from the same CAPS marker contig. XTa5DS-2754099_kasp23 was tested in Aegilops umbellulata, Ae. geniculata, Ae. peregrina and Ae. caudata derived alien introgression lines, which harbour four pairs of linked leaf and stripe rust genes; Lr76-Yr70, Lr57-Yr40, LrP- YrP, LrAc-YrAc, respectively. This KASP marker was found to be effective for the selection of the aforesaid four pairs of leaf rust and stripe rust resistance genes. Further, we tested and validated XTa5DS-2754099_kasp23 on commercial varieties and advanced breeding lines from four countries (India, Egypt, Australia and UK) including hexaploid and durum wheat. Our results provide evidence that KASP marker, XTa5DS-2754099_kasp23 can be used in marker-assisted selection of the four pairs of rust resistance alien genes in wheat breeding programmes.

An approach for high-resolution genetic mapping of distant wild relatives of bread wheat: example of fine mapping of Lr57 and Yr40 genes.

The article reports a powerful but simple approach for high-resolution mapping and eventual map-based cloning of agronomically important genes from distant relatives of wheat, using the already existing germplasm resources. Wild relatives of wheat are a rich reservoir of genetic diversity for its improvement. The effective utilization of distant wild relatives in isolation of agronomically important genes is hindered by the lack of recombination between the homoeologous chromosomes. In this study, we propose a simple yet powerful approach that can be applied for high-resolution mapping of a targeted gene from wheat's distant gene pool members. A wheat-Aegilops geniculata translocation line TA5602 with a small terminal segment from chromosome 5Mg of Ae. geniculata translocated to 5D of wheat contains genes Lr57 and Yr40 for leaf rust and stripe rust resistance, respectively. To map these genes, TA5602 was crossed with a susceptible Ae. geniculata 5Mg addition line. Chromosome pairing between the 5Mg chromosomes of susceptible and resistant parents resulted in the development of a high-resolution mapping panel for the targeted genes. Next-generation-sequencing data from flow-sorted 5Mg chromosome of Ae. geniculata allowed us to generate 5Mg-specific markers. These markers were used to delineate Lr57 and Yr40 genes each to distinct ~ 1.5Mb physical intervals flanked by gene markers on 5Mg. The method presented here will allow researchers worldwide to utilize existing germplasm resources in genebanks and seed repositories toward routinely performing map-based cloning of important genes from tertiary gene pools of wheat.

Phenotypic Diversity and Productivity of Medicago sativa Subspecies from Drought-Prone Environments in Mediterranean Type Climates.

The phenotypic diversity and productivity of a diverse alfalfa (M. sativa subspp.) panel of cultivars, landraces and wild relatives with putative drought tolerance were evaluated in two Mediterranean environments (central Chile and Southern Australia). In Chile, 70 accessions were evaluated in rainfed conditions and in Australia 30 accessions under rainfed and irrigated conditions, during three growing seasons. Large phenotypic variation was observed among and within subspecies for NDVI, stem length, intercepted PAR and forage yield. Principal component analysis indicated that the first two principal components (PC) accounted for 84.2% of total variance; fall dormancy, taxa, and breeding status were closely related to the agronomical performance of alfalfa accessions. Forage yield varied largely among accessions across years and locations. A linear relationship was found between annual forage yield and annual water added to the experiments (R2 = 0.60, p < 0.001). The GxE analysis for forage yield allowed the detection of the highest yielding accessions for each of the two mega-environments identified. The accessions CTA002 and CTA003 showed greater forage yield in both Chile and Australia environments. It is concluded that new breeding lines derived from crosses between cultivated alfalfa (M. sativa subsp. sativa) and wild relatives belonging to the primary (M. sativa subsp. falcata) and tertiary (M. arborea) gene pool, achieve outstanding agronomical performance in drought-prone environments.

Introgressive Hybridization of Common Wheat: Results and Prospects

This review is devoted to the introgressive hybridization of common wheat, the process of integrating the genes of other cultivated or wild species from the secondary and tertiary gene pools into its genome in order to increase the genetic diversity of this most important agricultural crop. The results achieved in the introgressive hybridization of common wheat over the past 20 years are summarized, the distribution of alien translocations by subgenomes and chromosomes of common wheat is analyzed, and the possibilities for further development of this direction of research and selection based on the use of alien genetic material are discussed.

Status of the Ex Situ and In Situ Conservation of Brazilian Crop Wild Relatives of Rice, Potato, Sweet Potato, and Finger Millet: Filling the Gaps of Germplasm Collections

This study presents the status of ex situ and in situ conservation for the crop wild relatives of rice, potato, sweet potato, and finger millet in Brazil, and the subsequent germplasm collection expeditions. This research is part of a global initiative entitled “Adapting Agriculture to Climate Change: Collecting, Protecting, and Preparing Crop Wild Relatives” supported by the Global Crop Diversity Trust. Species of the primary, secondary, and tertiary gene pools with occurrences reported in Brazil were included: Oryza alta Swallen, O. grandiglumis (Döll) Prod., O. latifolia Desv., O. glumaepatula Steud., Eleusine tristachya (Lam.) Lam., E. indica (L.) Gaertn., Solanum commersonii Dunal, S. chacoense Bitter, Ipomoea grandifolia (Dammer) O’Donell, I. ramosissima (Poir.) Choisy, I. tiliacea (Willd.) Choisy, I. triloba L., and I. cynanchifolia Meisn. The status of the ex situ and in situ conservation of each taxon was assessed using the gap analysis methodology, and the results were used to plan 16 germplasm collection expeditions. Seeds of the collected material were evaluated for viability, and the protocols for seed germination and cryopreservation were tested. The final conservation score, resulting from the gap analysis and including the average of the ex situ and in situ scores, resulted in a classification of medium priority of conservation for all the species, with the exception of I. grandifolia (high priority). The total accessions collected (174) almost doubled the total accessions of these crop wild relatives incorporated in Embrapa’s ex situ conservation system prior to 2015. In addition, accessions for practically absent species were collected for the ex situ conservation system, such as Ipomoea species, Eleusine indica, and Solanum chacoense. The methods used for dormancy breaking and low temperature conservation for the Oryza, Eleusine, and Ipomoea species were promising for the incorporation of accessions in the respective gene banks. The results show the importance of efforts to collect and conserve ex situ crop wild relatives in Brazil based on previous gap analysis. The complementarity with the in situ strategy also appears to be very promising in the country.

Take-All Disease: New Insights into an Important Wheat Root Pathogen.

Take-all disease, caused by the fungal root pathogen Gaeumannomyces tritici, is considered to be the most important root disease of wheat worldwide. Here we review the advances in take-all research over the last 15 years, focusing on the identification of new sources of genetic resistance in wheat relatives and the role of the microbiome in disease development. We also highlight recent breakthroughs in the molecular interactions between G. tritici and wheat, including genome and transcriptome analyses. These new findings will aid the development of novel control strategies against take-all disease. In light of this growing understanding, the G. tritici-wheat interaction could provide a model study system for root-infecting fungal pathogens of cereals.

Introgression of anthracnose resistance into the background of locally adapted common bean landraces

Adequate knowledge, access and introgression of genetic diversity available in cultivated and wild relatives are pre-requisites for widening the genetic base of cultivars to sustain genetic improvement. An attempt was made to screen anthracnose resistance in 33 indigenous and exotic accessions of common bean (Phaseolus vulgaris L.) belonging to primary, secondary, tertiary and quaternary gene pools including three popular and widely cultivated landraces of North-Western Indian Himalayas. The cultivated and wild species of common bean were introgressed into the backgrounds of landraces, which resulted in the development of 22 crosses comprising 6 each of intra and interspecific crosses with P. vulgaris and P. coccineus, 3 with P. acutifolius, 2 with P. lunatus and 5 backcrosses. The hybridity of these crosses was confirmed using morphological and molecular markers. The interspecific crosses of P. vulgaris × P. coccineus, P. vulgaris × P. acutifolius and P. vulgaris × P. lunatus were attempted for the first time in India using in-vitro approaches. Further hybrid plants were grown to maturity following embryo rescue protocol, but all showed different developmental abnormalities. The overall establishment of successful hybrids and their complete development was the maximum in cross of Bhaderwah Local × Poonch Local (18.28%) and the minimum in Bhaderwah Local × IC258276 and Bhaderwah Local × IC328372 (0.5%). The results of the present study revealed that wild relatives of common bean viz. P. coccineus, P. acutifolius and P. lunatus are an excellent source of resistance against anthracnose, which can be exploited for diversification of cultivated gene pool. These resistant genetic resources could also be shared among common bean researchers in the country or elsewhere under Standard Material Transfer Agreement for strengthening ongoing crop improvement programmes.

Host plant resistance in wheat to barley yellow dwarf viruses and their aphid vectors: a review.

Cereal aphids are vectors of at least 11 species of Barley Yellow Dwarf Viruses (BYDV) in wheat that alone and/or in combination can cause between 5%-80% grain yield losses. They establish complex virus-vector interactions, with variations in specificity and transmission efficiency that need to be considered for control purposes. In general, these viruses and vectors have a global distribution, however, BYDV-PAV is the most prevalent and abundant virus species worldwide, likely due to its vectoring efficiency and the wide distribution of its primary vector Rhopalosiphum padi. Host plant resistance (HPR) is an environmentally friendly, efficient and cost-effective tool to reduce crop losses to biotic stressors such as aphids and viruses. Finding resistance sources is paramount to breed for HPR. Currently, most of the resistance identified for aphids and BYDV derives from wheat related and wild relative species. However, breeding for HPR to BYDV and its vectors has additional challenges besides the source identification, for example, the lack of selection tools for certain aphid species, which likely prevents the development of elite wheat germplasm carrying resistance to these constraints. Nonetheless, modern technologies such as high-throughput phenotyping, genomic and advanced statistical tools can contribute to make HPR to aphids and BYDV more efficient. In the present review we describe the main sources of resistance, discuss the challenges and opportunities for incorporating the resistance in wheat breeding programs and present a workflow to breed for BYDV and its vectors in wheat.

Characterization and identification of annual wildCicerspecies for seed protein and mineral concentrations for chickpea improvement

AbstractDeveloping nutrient‐rich crop cultivars is the most economic strategy to combat malnutrition resulting from protein and mineral deficiencies. Chickpea (Cicer arietinumL.) is an important staple grain legume source of good quality dietary protein around the world, particularly in southern Asia, northern Africa, and the Middle East. In the present investigation, the genetic variability for protein and mineral concentrations was studied in 41 accessions of cultivated chickpea and eight annual wildCicerspecies of primary, secondary, and tertiary gene pool. Large variability was observed between and withinCicerspecies for seed protein, Fe, Zn, Cu, Mn, Ca, and Mg concentration with high heritability.C. chorassanicum(Bunge) Popov was found to be the most promising species for high seed protein and Ca;C. judaicumBoiss. for high seed Fe, Cu. and Mg;C. yamashiataeKitam. for high seed Zn and Fe; andC. pinnatifidumJaub. &amp; Spach for high seed Mn concentrations. All the wildCiceraccessions except ICC20190 (C. echinospermumP. H. Davis) had high concentration of at least one or more seed nutrients. WildCiceraccessions such as ICC17141 (C. chorassanicum), ICC17269 and ICC17303 (bothC. pinnatifidum), ICC17261 and ICC17262 (C. reticulatum), ICC20236 (C. chorassanicum), and ICC17117 and ICC17281 (C. yamashitae) were found promising for multiple seed nutrients. AsC. reticulatumLadiz. andC. echinospremumaccessions are crossable with cultivated chickpea, promisingC. reticulatumaccessions identified in the present study can be used in crossing program for developing new nutrient‐rich chickpea cultivars.

Cross-species Amplification and Molecular Diversity Analysis in Greengram [Vigna radiata (L.) Wilczek] and Ricebean [Vigna umbellata Thunb.

Background: Greengram is the fourth dominant pulse crop grown in India and is highly susceptible to bruchids and yellow mosaic virus. Ricebean belonging to the tertiary genepool of greengram shows resistance to this pest and disease. Ricebean being a minor pulse crop has limited SSR markers. Hence, the present study was conducted to test the cross-species amplification of SSR markers derived from related species which could be helpful in studying the molecular diversity available in each crop and for molecular confirmation of the inter- and intra-specific hybrid developed from the crosses.Methods: Molecular diversity analysis was carried out using 30 genotypes belonging to two species of Vigna (V. radiata and V. umbellata) based on 20 SSR primers derived from adzukibean, commonbean and greengram. Result: Cross species amplification was observed for all the SSR primers pairs used. The number of alleles detected varied from one (VJ 31122A) to four (CEDAAG 001 and MB 91) with an average of 2.55 alleles per primer. Allele size varied from 100 to 292 bp. The PIC value ranged from zero to 0.611 with an average value of 0.377. Dendrograms constructed based on UPGMA and Neighbour-Joining tree method, grouped the genotypes into five clusters and five groups, respectively. The V. umbellata genotypes were grouped in separate cluster from the V. radiata genotypes in both the methods. The obtained DNA polymorphism at intra- and inter-specific level will facilitate the application of molecular breeding approaches for greengram improvement.

Characterization and pre‐breeding of diverse alfalfa wild relatives originating from drought‐stressed environments

AbstractChanging climates and associated increased variability pose risks to alfalfa (Medicago sativa L.) cultivation, with the requirement to establish, survive, and maintain production under water stress. Crop wild relatives (CWR) of alfalfa include populations that have evolved to survive in a number of different, extreme environments, but until recently have had limited use in breeding programs. Here we report on the phenotypic diversity of alfalfa crop wild relatives that were selected to represent extremes in drought tolerance (by sourcing germplasm from environments with extremes in low rainfall, high temperature, shallow soils, and winter freezing) with the aim of providing germplasm with drought tolerance and improved forage yield traits for breeding programs in both warm and cool dry temperate environments. Newly formed hybrids created between M. sativa, M. arborea L. (a woody shrub), and M. truncatula Gaertn. (an annual species from the Mediterranean region) were developed or acquired to introduce new genetic diversity from the tertiary genepool. Preliminary characterization and evaluation was used for taxonomic classification, and to identify wild accessions and pre‐bred (hybrid) lines that offer new diversity for growth habit, seed size, fall dormancy, and forage yield. The accessions and pre‐breeding lines described have been donated to the Australian Pastures Genebank for conservation and distribution.

Evaluation of wild perennial Glycine species for resistance to soybean cyst nematode and soybean rust

AbstractThe genetic base for soybean cultivars is narrow compared to most other crop species. Twenty‐seven wild perennial Glycine species comprise the tertiary gene pool to soybean that may contain many genes of economic importance for soybean improvement. We evaluated 16 accessions of G. argyrea, G. clandestina, G. dolichocarpa, and G. tomentella for resistance to Heterodera glycines (HG), also known as the soybean cyst nematode, and to multiple isolates of Phakopsora pachyrhizi, the causal fungus of soybean rust. All 16 accessions were classified as resistant to H. glycines HG Type 2.5.7, based on number of cysts per root mass with plant introductions (PIs) 483227, 509501, 563892, and 573064 (all G. tomentella) void of any cysts indicating no reproduction by this pest. All 16 accessions had an immune reaction to one isolate of P. pachyrhizi. Regardless of isolate, no sporulating uredinia were observed on G. argyrea (PI 505151) and G. tomentella (PIs 483227, 509501, and 573064). These results demonstrate that some accessions within the perennial Glycine species harbour resistance to both H. glycines and P. pachyrhizi and would be good candidates for wide hybridization programs seeking to transfer potentially unique multiple resistance genes into soybean.

Crop wild phylorelatives (CWPs): phylogenetic distance, cytogenetic compatibility and breeding system data enable estimation of crop wild relative gene pool classification

AbstractEnabling food security requires access to a broad range of genetic resources to facilitate crop breeding. This need is increased in a climate change scenario, which will require the production of novel crops adapted to new conditions. However, many major crops have reduced genetic diversity due to the genetic bottlenecks that they have experienced during their domestication and subsequent breeding. Crop wild relatives (CWRs) remain underexploited in plant breeding programmes, mostly because of the lack of knowledge of their cross-compatibility with crops. In this study, we use a combination of phylogenetic distance metrics, cytogenetic compatibility data (e.g. chromosome number and ploidy) and information about breeding systems to predict interspecific cross-compatibility between crop and wild species and hence identify crop wild phylorelatives (CWPs) (i.e. CWRs that can breed with the crop). We illustrate this concept using cultivated asparagus as a model by integrating previous cross-compatibility knowledge and CWR classifications into a phylogenetic framework reconstructed using available sequence data. Our approach aims to reinforce the use of the gene pool classification system of CWRs of Harlan and De Wet, since CWPs are estimated to belong to the secondary gene pool and non-CWPs to the tertiary gene pool. Identifying CWPs unlocks novel uses of genetic resources, although such data are available for less than half of the known CWRs (43.4% with sequence data and 32.5% with known ploidy). The need to conserve plants that provide or enhance provisioning ecosystem services, including CWRs, is clear if we are to rise to the global challenge of ensuring food security for all. However, basic knowledge about their conservation status is still lacking, with only c. 20% of CWRs assigned an IUCN red list assessment, 23% of which are Data Deficient (DD). Using the CWP classification presented here to define CWRs will contribute towards helping to prioritize CWRs for IUCN assessments and, where prioritised, conservation.