Research notes: Cytology of soybean haploid progeny

Haploids are being isolated annually among individuals obtained from polyembryonic seeds associated with the North Carolina male sterile (ms1). The haploids are being used to obtain aneuploids. In 1976 and 1977, 7,206 and 15,530 seeds, respectively, were obtained from male sterile plants (ms1 North Carolina) representing Maturity Groups I- V

The balance between N-cadherin and E-cadherin orchestrates major neuroectodermal cell fate choices

Numerous cadherin proteins, including N‐cadherin (Ncad), E‐cadherin (Ecad), Cadherin‐11 (Cad11) and Cadherin‐7 (Cad7), are expressed in the developing neural plate as well as in neural crest cells as they delaminate from the newly closed neural tube. To clarify whether these proteins function independently or coordinately during development, we examined their relative expression in the cranial region of chick embryos. The results revealed surprising overlap of Ecad, Ncad and Cad7 in the neural tube, suggesting possible heterotypic interactions. Using a proximity ligation assay and co‐immunoprecipitation to test this hypothesis, we found that Ncad formed heterophilic complexes in the developing neural tube with Ecad. We also determined that modulation of either Ncad or Ecad levels led to reciprocal gain or reduction of the other cadherin protein. Altering levels of the two cadherin proteins affected the early fate specification of ectodermal derivatives, forcing an aberrant choice between neural crest and epidermal cells. Finally, we identified that the availability of β‐catenin plays a critical role in maintaining the balance between Ncad and Ecad in early development since co‐expression of activated β‐catenin rescues the Ncad‐overexpression phenotype. These results suggest that β‐catenin‐mediated balance of Ncad and Ecad proteins is critical for the normal development of the three ectodermal derivatives

Wind-tunnel/flight correlation study of aerodynamic characteristics of a large flexible supersonic cruise airplane (XB-701) 2: Extrapolation of wind-tunnel data to full-scale conditions

The results of calculations necessary to extrapolate performance data on an XB-70-1 wind tunnel model to full scale at Mach numbers from 0.76 to 2.53 are presented. The extrapolation was part of a joint program to evaluate performance prediction techniques for large flexible supersonic airplanes similar to a supersonic transport. The extrapolation procedure included: interpolation of the wind tunnel data at the specific conditions of the flight test points; determination of the drag increments to be applied to the wind tunnel data, such as spillage drag, boundary layer trip drag, and skin friction increments; and estimates of the drag items not represented on the wind tunnel model, such as bypass doors, roughness, protuberances, and leakage drag. In addition, estimates of the effects of flexibility of the airplane were determined

Genomic Selection for Crop Improvement: An Introduction

Marker-assisted selection (MAS) exploits the markers associated with traits of interest for selecting lines with superior alleles for developing improved lines. However use of MAS is restricted to simple traits due to its inability to handle complex traits. Advancements in genomics technologies have been able to dramatically reduce the cost of genotyping, enabling the use of genome-wide marker data for selecting lines with higher breeding value. Genomic selection (GS), a modern breeding approach that uses genome-wide marker data to estimate the breeding value and has the potential to address the complex traits. GS exploits the genotyping and phenotyping data on a training population to train the prediction models to calculate the genomic estimated breeding value (GEBV). GS has the capability to reduce selection cycle duration and increase selection accuracy, intensity, efficiency, and gains per unit of time, thereby enhancing the rate of genetic gains. Availability of cost-effective genotyping platforms has enabled the cost-effective generation of large-scale genotyping data, facilitating the deployment of GS in several crop species. This chapter provides an introduction to the book, highlighting the basic and advanced principles of GS breeding and its applications for crop improvement

Genomic Selection for Crop Improvement: New Molecular Breeding Strategies for Crop Improvement

Genomic Selection for Crop Improvement serves as handbook for users by providing basic as well as advanced understandings of genomic selection. This useful review explains germplasm use, phenotyping evaluation, marker genotyping methods, and statistical models involved in genomic selection. It also includes examples of ongoing activities of genomic selection for crop improvement and efforts initiated to deploy the genomic selection in some important crops. In order to understand the potential of GS breeding, it is high time to bring complete information in the form of a book that can serve as a ready reference for geneticist and plant breeders

Genomics-assisted breeding for crop improvement

Genomics research is generating new tools, such as functional molecular markers and informatics, as well as new knowledge about statistics and inheritance phenomena that could increase the efficiency and precision of crop improvement. In particular, the elucidation of the fundamental mechanisms of heterosis and epigenetics, and their manipulation, has great potential. Eventually, knowledge of the relative values of alleles at all loci segregating in a population could allow the breeder to design a genotype in silico and to practice whole genome selection. High costs currently limit the implementation of genomics-assisted crop improvement, particularly for inbreeding and/or minor crops. Nevertheless, marker-assisted breeding and selection will gradually evolve into ‘genomics-assisted breeding’ for crop improvement

Durum Wheat Landraces from East and West Regions of the Mediterranean Basin Are Genetically Distinct for Yield Components and Phenology

Genetic diversity of durum wheat landraces is a powerful tool for the introgression of new alleles of commercial interest in breeding programs. In a previous study, our team structured a collection of 172 durum wheat landraces from 21 Mediterranean countries in four genetic populations related to their geographical origin: east Mediterranean (17), east Balkan and Turkey (23), west Balkan and Egypt (25), and West Mediterranean (73), leaving 34 genotypes as admixed, and association mapping was carried out for important agronomic traits. Using a subset of this collection, the current study identified 23 marker alleles with a differential frequency in landraces from east and west regions of the Mediterranean Basin, which affected important agronomic traits. Eastern landraces had higher frequencies than the western ones of alleles increasing the number of spikes (wPt-5385 on chromosome 1B), grains per m2 (wPt-0841 on chromosome 7B), and grain filling duration (7 significant marker trait associations). Eastern landraces had higher frequencies of marker alleles located on chromosomes 4A, 5B, and 6B associated with reduced cycle length, and lighter grains than the western ones. Also for lower kernel weight, four marker alleles were located on chromosome 1A. Breeders may use the molecular markers identified in the current study for improving yield under specific Mediterranean environmentsinfo:eu-repo/semantics/publishedVersio

Can genomics deliver climate-change ready crops?

Development of climate resilient crops with accelerating genetic gains in crops will require integration of different disciplines/technologies, to see the impact in the farmer’s field. In this review, we summarize how we are utilizing our germplasm collections to identify superior alleles/haplotypes through NGS based sequencing approaches and how genomics-enabled technologies together with precise phenotyping are being used in crop breeding. Pre-breeding and genomics-assisted breeding approaches are contributing to the more efficient development of climate-resilient crops. It is anticipated that the integration of several disciplines/ technologies will result in the delivery of climate change ready crops in less time

Effectiveness of Genomic Prediction of Maize Hybrid Performance in Different Breeding Populations and Environments

Genomic prediction is expected to considerably increase genetic gains by increasing selection intensity and accelerating the breeding cycle. In this study, marker effects estimated in 255 diverse maize (Zea mays L.) hybrids were used to predict grain yield, anthesis date, and anthesis-silking interval within the diversity panel and testcross progenies of 30 F(2)-derived lines from each of five populations. Although up to 25% of the genetic variance could be explained by cross validation within the diversity panel, the prediction of testcross performance of F(2)-derived lines using marker effects estimated in the diversity panel was on average zero. Hybrids in the diversity panel could be grouped into eight breeding populations differing in mean performance. When performance was predicted separately for each breeding population on the basis of marker effects estimated in the other populations, predictive ability was low (i.e., 0.12 for grain yield). These results suggest that prediction resulted mostly from differences in mean performance of the breeding populations and less from the relationship between the training and validation sets or linkage disequilibrium with causal variants underlying the predicted traits. Potential uses for genomic prediction in maize hybrid breeding are discussed emphasizing the need of (1) a clear definition of the breeding scenario in which genomic prediction should be applied (i.e., prediction among or within populations), (2) a detailed analysis of the population structure before performing cross validation, and (3) larger training sets with strong genetic relationship to the validation set

Physiological genetics of aluminum tolerance in the wheat cultivar Atlas 66

Aluminum toxicity limits wheat (Triticum aestivum L.) production on acidic soils. The wheat cultivar Atlas 66 reportedly may have both more than one Al tolerance gene and more than one Al tolerance mechanism. The purpose of this study was to identify the Al tolerance mechanisms conferred by the individual Atlas 66 Al tolerance genes present in near-isogenic lines (NILs) of the cv. Century and Chisholm ('Century-T' and 'Chisholm-T'). Seedling hydroponic culture analysis revealed that the NILs were not as Al tolerant, nor were they able to exclude Al from root apices as effectively as Atlas 66. Al-inducible malate release from root apices was significantly higher in the NILs compared with the recurrent parents, but less than that observed in Atlas 66. In contrast, root phosphate release was significantly lower than previously reported in Atlas 66, with no major differences observed among lines. These results indicate that the Atlas 66 Al tolerance gene present in each NIL acts by increasing Al-inducible malate release from root tips, but confers only a portion of the Al tolerance of Atlas 66 in both instances. Thus, differences in Al tolerance between the NILs and Atlas 66 can be attributed to malate release differences, and not differential phosphate release. Further, these results indicate that genetic variation at more than one locus underlies the malate- mediated Al tolerance differences in Atlas 66, when compared with Century and Chisholm. The Atlas 66 alleles for these loci have not been introgressed into the NILs.Peer reviewedPlant and Soil Science