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Wheat (Triticum sp.) is one of the world’s most important crops, and constantly increasing its productivity is crucial to the livelihoods of millions of people. However, more than a century of intensive breeding and selection processes have eroded genetic diversity in the elite genepool, making new genetic gains difficult. Therefore, the need to introduce novel genetic diversity into modern wheat has become increasingly important. This review provides an overview of the plant genetic resources (PGR) available for wheat. We describe the most important taxonomic and phylogenetic relationships of these PGR to guide their use in wheat breeding. In addition, we present the status of the use of some of these resources in wheat breeding programs. We propose several introgression schemes that allow the transfer of qualitative and quantitative alleles from PGR into elite germplasm. With this in mind, we propose the use of a stage-gate approach to align the pre-breeding with main breeding programs to meet the needs of breeders, farmers, and end-users. Overall, this review provides a clear starting point to guide the introgression of useful alleles over the next decade.

Due to the low genetic diversity in the current wheat germplasm, gene mining from wild relatives is essential to develop new wheat cultivars that are more resilient to the changing climate. Aegilops tauschii , the D-genome donor of bread wheat, is a great gene source for wheat breeding; however, identifying suitable genes from Ae. tauschii is challenging due to the different morphology and the wide intra-specific variation within the species. In this study, we developed a platform for the systematic evaluation of Ae. tauschii traits in the background of the hexaploid wheat cultivar ‘Norin 61’ and thus for the identification of QTLs and genes. To validate our platform, we analyzed the seed dormancy trait that confers resistance to preharvest sprouting. We used a multiple synthetic derivative (MSD) population containing a genetic diversity of 43 Ae. tauschii accessions representing the full range of the species. Our results showed that only nine accessions in the population provided seed dormancy, and KU-2039 from Afghanistan had the highest level of seed dormancy. Therefore, 166 backcross inbred lines (BILs) were developed by crossing the synthetic wheat derived from KU-2039 with ‘Norin 61’ as the recurrent parent. The QTL mapping revealed one novel QTL, Qsd.alrc.5D , associated with dormancy explaining 41.7% of the phenotypic variation and other five unstable QTLs, two of which have already been reported. The Qsd.alrc.5D , identified for the first time within the natural variation of wheat, would be a valuable contribution to breeding after appropriate validation. The proposed platform that used the MSD population derived from the diverse Ae. tauschii gene pool and recombinant inbred lines proved to be a valuable platform for mining new and important QTLs or alleles, such as the novel seed dormancy QTL identified here. Likewise, such a platform harboring genetic diversity from wheat wild relatives could be a useful source for mining agronomically important traits, especially in the era of climate change and the narrow genetic diversity within the current wheat germplasm.

Inbreeding depression (ID) is caused by increased homozygosity in the offspring after selfing. Although the self-compatible, highly heterozygous, tetrasomic polyploid potato (Solanum tuberosum L.) suffers from ID, some argue that the potential genetic gains from using inbred lines in a sexual propagation system of potato are too large to be ignored. The aim of this research was to assess the effects of inbreeding on potato offspring performance under a high latitude and the accuracy of the genomic prediction of breeding values (GEBVs) for further use in selection. Four inbred (S1) and two hybrid (F1) offspring and their parents (S0) were used in the experiment, with a field layout of an augmented design with the four S0 replicated in nine incomplete blocks comprising 100, four-plant plots at Umeå (63°49′30″ N 20°15′50″ E), Sweden. S0 was significantly (p < 0.01) better than both S1 and F1 offspring for tuber weight (total and according to five grading sizes), tuber shape and size uniformity, tuber eye depth and reducing sugars in the tuber flesh, while F1 was significantly (p < 0.01) better than S1 for all tuber weight and uniformity traits. Some F1 hybrid offspring (15–19%) had better total tuber yield than the best-performing parent. The GEBV accuracy ranged from −0.3928 to 0.4436. Overall, tuber shape uniformity had the highest GEBV accuracy, while tuber weight traits exhibited the lowest accuracy. The F1 full sib’s GEBV accuracy was higher, on average, than that of S1. Genomic prediction may facilitate eliminating undesired inbred or hybrid offspring for further use in the genetic betterment of potato.

Background/Objective: Salinity is a growing problem affecting a large portion of global agricultural land, particularly in areas where water resources are scarce. The objective of this study was to provide physiological and molecular information on salttolerant citrus rootstocks to mitigate the detrimental effects of salinity on citriculture. Methods: Ten accessions belonging to eight Citrus species and four to Poncirus trifoliata Raf. were tested for salinity tolerance (0 and 15 mM NaCl for 1 year) in terms of vegetative and Cl− tissue distribution traits. In addition, most accessions were evaluated for leaf Na+ and other cations. Results: All salt tolerant accessions tended to restrict the leaf Cl− content, although in a lower degree than the Cleopatra mandarin. However, differences in their ability to restrict leaf [Na+] were evident, contributing to a classification of trifoliate and sour orange accessions that matched their genotypic grouping based on allele sharing at a marker targeting candidate gene coding for the NPF5.9 transporter within LCL-6 quantitative trait locus. Conclusions: Our markers targeting LCl-6 candidate genes coding for NPF5.9, PIP2.1, and CHX20 (citrus GmSALT3 ortholog) could be efficient tools for managing the detected salt tolerance diversity in terms of both Cl− and Na+ homeostasis in rootstock breeding programs derived from these species, in addition to Citrus reshni.

In order to breed broccoli and other Brassica materials to be highly resistant to clubroot disease, 41 Brassicaceae varieties were developed and identified between 2020 and 2021. Seven known clubroot genes were used for screening these materials. In addition, the resistant and susceptible broccoli cultivars were designed for observing their differences in the infection process with Plasmodiophora brassicae. The results showed that 90% of total materials had carried more than two clubroot resistance genes: one material carried two disease resistance genes, four materials carried seven genes for clubroot resistance, two materials carried six genes for clubroot resistance, and in total 32% of these materials carried five genes for clubroot resistance. As a result, several new genotypes of Brassicaceae germplasm were firstly created and obtained based on distant hybridization and identification of loci conferring resistance against Plasmodiophora brassicae in this study. We found and revealed that similar infection models of Plasmodiophora brassicae occurred in susceptible and resistant cultivars of broccoli, but differences in infection efficiency of Plasmodiophora brassicae also existed in both materials. For resistant broccoli plants, a small number of conidia formed in the root hair, and only a few spores could enter the cortex without forming sporangia while sporangia could form in susceptible plants. Our study could provide critical Brassica materials for breeding resistant varieties and new insight into understanding the mechanism of plant resistance.

Established allopolyploid species often contain specific gene(s) dedicated to suppressing the pairing of homoeologous chromosomes during meiosis. A longstanding question is whether such genes in allopolyploids with lower ploidy levels can retain full functionality when the ploidy level rises following the addition of a new subgenome during outcrossing. Here, we addressed this question by generating a synthetic allohexaploid wheat species, Triticum kiharae (GGAADD), by crossing the allotetraploid Triticum timopheevii (GGAA) to the diploid Aegilops tauschii (DD), followed by colchicine-induced chromosomal doubling. The gene Pairing homoeologous 1 (Ph1) inherited from T. timopheevii was likely hypofunctional in nascent T. kiharae, as evidenced by irregularities during meiotic chromosome pairing and organismal numerical and structural chromosome variation in selfed progeny populations. The allohexaploidization event also induced substantial rewiring of gene expression among homoeologs and nonadditive gene expression, leading to distinct predicted biological functions for differentially expressed genes (DEGs) when they were partitioned into the subgenomes. F1 hybrids from a cross between T. kiharae and bread wheat (T. aestivum, BBAADD) were male-sterile but female-fertile, confirming intrinsic postzygotic reproductive isolation between the two species while enabling backcrossing of these sterile F1 hybrids to bread wheat. These features provide a feasible route to simultaneously introgress standing congeneric genetic variations from both T. timopheevii and Ae. tauschii, as well as heritable de novo variations that have arisen in T. kiharae into bread wheat.

The development of sugar beet as an economically important field crop coincided with our increased understanding of modern genetic principles. It was developed in the late 1700s from white fodder beet; therefore, the genetic base of sugar beet is thought to be narrower than many open-pollinated crops. The wild sea beet is the progenitor of all domesticated beet and cross compatible with cultivated beet (domestic and cultivated are given subspecies level in the same species). The breeding system of sugar beet is complex and the crop is biennial, which lengthens the generation time to almost 1 year. A genetic-cytoplasmic male sterility (CMS) system is utilized for commercial hybrid production. Early breeding objectives were to improve the concentration and extractability of sucrose and little emphasis was placed on host-plant resistance to insect, nematode, and disease pests. As production areas expanded, these pests limited production, sometimes severely. The first systematic attempts to screen exotic and wild beet germplasm for disease resistance were initiated early in the 20th century. Many undesirable traits from wild beet were reportedly introgressed with the selected disease resistance and it was only in the late 1900s that the use of wild beet genetic resources became common place in public breeding programs. In North America, a pivotal development in utilizing the genetic resources available for sugar beet breeding was the formation in 1983 of the Sugarbeet Crop Germplasm Committee (CGC). Since the Sugarbeet CGC identified enhancing the commercial sugar beet germplasm pool as a high priority, there has been an aggressive evaluation of the National Plant Germplasm System (NPGS) Beta collection. This collection now has more than 2500 accessions from within the genus Beta. In 2002, it was estimated that close to 25,000 evaluation data points (descriptors x accessions evaluated) describing the collection were available in the Genetic Resources Information Network (GRIN) database. Over 3000 evaluations described levels of resistance of sugar beet and wild beet accessions to 10 major disease and insect pests of sugar beet. As soon as the evaluation data are collected, they are used to select the sources for the pre-breeding programs. There is a lag time in sugar beet of 8-15 years between starting a germplasm development program and releasing the first germplasm, but successes of this program are available in the germplasm released to the commercial breeders. Resistance genes from wild beet for rhizomania and beet cyst nematode resistance have been commercialized.

A perennial version of grain sorghum [ S. bicolor (L.) Moench] would create opportunities for greatly reducing tillage and preventing soil degradation. Efforts to select for perenniality and grain production among progeny of hybrids between S. bicolor (2n = 20) and the weedy tetraploid perennial S. halepense (L.) Pers. (2n = 40) are complicated in that F 1 hybrids produced by diploid × tetraploid sorghum crosses are usually tetraploid. In 2013, a set of random pollinations between 19 diploid cytoplasmic male-sterile inbred lines and 43 tetraploid perennial plants produced 165 F 1 hybrid plants, more than 75% of which had highly atypical plant, panicle, and seed phenotypes. Phenotypic segregation in F 2 populations derived from atypical hybrids was also anomalous. Examination of mitotic metaphase cells in F 1 or F 2 root tips revealed that 129 of the 165 hybrids were diploid. Parentage of the diploid progenies was confirmed using simple-sequence repeat analysis. The mechanism by which diploid hybrids arise from diploid × tetraploid crosses is unknown, but it may involve either production of monohaploid (n = 10) pollen by the tetraploid parent or chromosome elimination during early cell divisions following formation of the triploid zygote. The ability to produce diploid germplasm segregating for S. bicolor and S. halepense alleles could have great utility, both for the development of perennial sorghum and for the improvement of conventional grain sorghum.

Increasing levels of foliar resistance to late blight, caused by Phytophthora infestans, have previously been reported through two cycles of recurrent maternal half-sib selection in a diploid hybrid population of Solanum phureja-S. stenotomum. The objective of this study was to determine if continued improvements for resistance to late blight could be realized by another cycle of selection. Four clones from each of 72 maternal half-sib families constituting the cycle four population were evaluated for late blight resistance in replicated field trials in Pennsylvania in 2015 and 2016. The experimental design was a randomized complete block design with two replications each year. P. infestans US23 genotype was used in inoculations each year. Area under the disease progress curve (AUDPC) was calculated based on visual assessment of foliar disease five times late in the season each year and subjected to statistical and genetic analyses. Mean AUDPC in the cycle one, two, three, and four populations was 652, 556, 276, and 173, respectively. Narrow-sense heritability for resistance decreased in the cycle four population (h2 = 0.54) as compared to prior populations (0.77 ≤ h2 ≤ 0.80), however, broad-sense heritability remained high (H = 0.83). Additional improvements for late blight resistance are likely to occur if this approach is continued.

We characterized the genotypic and phenotypic variation in cell wall digestibility (CWD) and other agronomic traits of 50 backcross 1 generation doubled haploid (BC1DH) lines developed from the Germplasm Enhancement of Maize project. These lines were generated by introgressing 31 exotic unadapted maize races into PHZ51 and PHB47, temperate inbred lines with expired Plant Variety Protection. The 50 BC1DH lines and five check lines were genotyped with 199 single nucleotide polymorphism markers distributed across the genome. We identified, on average, 11.8% of markers with exotic donor parent alleles. This likely underestimates the proportion of donor introgressions, since we cannot discriminate monomorphic alleles from donor and recurrent parents. The potential roles of natural selection and the doubled haploid process in favouring selection of the recurrent genome are discussed. Although the proportion of donor parent genome was underestimated, donor fragments evaluated across the 50 BC1DH lines covered 92.9% of the recurrent parent genome. The evaluation of BC1DH lines for CWD revealed promising lines with CWD not differing significantly (α = 0.05) from forage quality lines used as checks. The introgression of exotic genome segments, however, was generally associated with higher ears, lodging, and late flowering. Even with limited power, our association analysis revealed quantitative trait polymorphisms associated with CWD, flowering date, and lodging.