Publications by authors named "Chin Jian Yang"

8 Publications

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Overcoming barriers to the registration of new plant varieties under the DUS system.

Commun Biol 2021 03 8;4(1):302. Epub 2021 Mar 8.

Scotland's Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh, EH9 3JG, UK.

Distinctness, Uniformity and Stability (DUS) is an intellectual property system introduced in 1961 by the International Union for the Protection of New Varieties of Plants (UPOV) for safeguarding the investment and rewarding innovation in developing new plant varieties. Despite the rapid advancement in our understanding of crop biology over the past 60 years, the DUS system has changed little and is still largely dependent upon a set of morphological traits for testing candidate varieties. As the demand for more plant varieties increases, the barriers to registration of new varieties become more acute and thus require urgent review to the system. To highlight the challenges and remedies in the current system, we evaluated a comprehensive panel of 805 UK barley varieties that span the entire history of DUS testing. Our findings reveal the system deficiencies such as inconsistencies in DUS traits across environments, limitations in DUS trait combinatorial space, and inadequacies in currently available DUS markers. We advocate the concept of genomic DUS and provide evidence for a shift towards a robust genomics-enabled registration system for new crop varieties.
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http://dx.doi.org/10.1038/s42003-021-01840-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7940638PMC
March 2021

Origin Specific Genomic Selection: A Simple Process To Optimize the Favorable Contribution of Parents to Progeny.

G3 (Bethesda) 2020 07 7;10(7):2445-2455. Epub 2020 Jul 7.

Scotland's Rural College (SRUC), Kings Buildings, West Mains Road, Edinburgh, EH9 3JG, UK,

Modern crop breeding is in constant demand for new genetic diversity as part of the arms race with genetic gain. The elite gene pool has limited genetic variation and breeders are trying to introduce novelty from unadapted germplasm, landraces and wild relatives. For polygenic traits, currently available approaches to introgression are not ideal, as there is a demonstrable bias against exotic alleles during selection. Here, we propose a partitioned form of genomic selection, called Origin Specific Genomic Selection (OSGS), where we identify and target selection on favorable exotic alleles. Briefly, within a population derived from a bi-parental cross, we isolate alleles originating from the elite and exotic parents, which then allows us to separate out the predicted marker effects based on the allele origins. We validated the usefulness of OSGS using two nested association mapping (NAM) datasets: barley NAM (elite-exotic) and maize NAM (elite-elite), as well as by computer simulation. Our results suggest that OSGS works well in its goal to increase the contribution of favorable exotic alleles in bi-parental crosses, and it is possible to extend the approach to broader multi-parental populations.
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http://dx.doi.org/10.1534/g3.120.401132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7341124PMC
July 2020

The genetic architecture of the maize progenitor, teosinte, and how it was altered during maize domestication.

PLoS Genet 2020 05 14;16(5):e1008791. Epub 2020 May 14.

Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

The genetics of domestication has been extensively studied ever since the rediscovery of Mendel's law of inheritance and much has been learned about the genetic control of trait differences between crops and their ancestors. Here, we ask how domestication has altered genetic architecture by comparing the genetic architecture of 18 domestication traits in maize and its ancestor teosinte using matched populations. We observed a strongly reduced number of QTL for domestication traits in maize relative to teosinte, which is consistent with the previously reported depletion of additive variance by selection during domestication. We also observed more dominance in maize than teosinte, likely a consequence of selective removal of additive variants. We observed that large effect QTL have low minor allele frequency (MAF) in both maize and teosinte. Regions of the genome that are strongly differentiated between teosinte and maize (high FST) explain less quantitative variation in maize than teosinte, suggesting that, in these regions, allelic variants were brought to (or near) fixation during domestication. We also observed that genomic regions of high recombination explain a disproportionately large proportion of heritable variance both before and after domestication. Finally, we observed that about 75% of the additive variance in both teosinte and maize is "missing" in the sense that it cannot be ascribed to detectable QTL and only 25% of variance maps to specific QTL. This latter result suggests that morphological evolution during domestication is largely attributable to very large numbers of QTL of very small effect.
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http://dx.doi.org/10.1371/journal.pgen.1008791DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266358PMC
May 2020

TeoNAM: A Nested Association Mapping Population for Domestication and Agronomic Trait Analysis in Maize.

Genetics 2019 11 3;213(3):1065-1078. Epub 2019 Sep 3.

Laboratory of Genetics, University of Wisconsin-Madison, Wisconsin 53706

Recombinant inbred lines (RILs) are an important resource for mapping genes controlling complex traits in many species. While RIL populations have been developed for maize, a maize RIL population with multiple teosinte inbred lines as parents has been lacking. Here, we report a teosinte nested association mapping (TeoNAM) population, derived from crossing five teosinte inbreds to the maize inbred line W22. The resulting 1257 BCS RILs were genotyped with 51,544 SNPs, providing a high-density genetic map with a length of 1540 cM. On average, each RIL is 15% homozygous teosinte and 8% heterozygous. We performed joint linkage mapping (JLM) and a genome-wide association study (GWAS) for 22 domestication and agronomic traits. A total of 255 QTL from JLM were identified, with many of these mapping near known genes or novel candidate genes. TeoNAM is a useful resource for QTL mapping for the discovery of novel allelic variation from teosinte. TeoNAM provides the first report that , a rice domestication gene, is also a QTL associated with tillering in teosinte and maize. We detected multiple QTL for flowering time and other traits for which the teosinte allele contributes to a more maize-like phenotype. Such QTL could be valuable in maize improvement.
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http://dx.doi.org/10.1534/genetics.119.302594DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6827374PMC
November 2019

The genetic architecture of teosinte catalyzed and constrained maize domestication.

Proc Natl Acad Sci U S A 2019 03 6;116(12):5643-5652. Epub 2019 Mar 6.

Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706;

The process of evolution under domestication has been studied using phylogenetics, population genetics-genomics, quantitative trait locus (QTL) mapping, gene expression assays, and archaeology. Here, we apply an evolutionary quantitative genetic approach to understand the constraints imposed by the genetic architecture of trait variation in teosinte, the wild ancestor of maize, and the consequences of domestication on genetic architecture. Using modern teosinte and maize landrace populations as proxies for the ancestor and domesticate, respectively, we estimated heritabilities, additive and dominance genetic variances, genetic-by-environment variances, genetic correlations, and genetic covariances for 18 domestication-related traits using realized genomic relationships estimated from genome-wide markers. We found a reduction in heritabilities across most traits, and the reduction is stronger in reproductive traits (size and numbers of grains and ears) than vegetative traits. We observed larger depletion in additive genetic variance than dominance genetic variance. Selection intensities during domestication were weak for all traits, with reproductive traits showing the highest values. For 17 of 18 traits, neutral divergence is rejected, suggesting they were targets of selection during domestication. Yield (total grain weight) per plant is the sole trait that selection does not appear to have improved in maize relative to teosinte. From a multivariate evolution perspective, we identified a strong, nonneutral divergence between teosinte and maize landrace genetic variance-covariance matrices (G-matrices). While the structure of G-matrix in teosinte posed considerable genetic constraint on early domestication, the maize landrace G-matrix indicates that the degree of constraint is more unfavorable for further evolution along the same trajectory.
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http://dx.doi.org/10.1073/pnas.1820997116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431195PMC
March 2019

Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time Adaptation.

Curr Biol 2018 09 13;28(18):3005-3015.e4. Epub 2018 Sep 13.

National Maize Improvement Center, Key Laboratory of Biology and Genetic Improvement of Maize (MOA), Beijing Key Laboratory of Crop Genetic Improvement, Joint International Research Laboratory of Crop Molecular Breeding, China Agricultural University, Beijing 100193, China. Electronic address:

Maize (Zea mays ssp. mays) was domesticated in southwestern Mexico ∼9,000 years ago from its wild ancestor, teosinte (Zea mays ssp. parviglumis) [1]. From its center of origin, maize experienced a rapid range expansion and spread over 90° of latitude in the Americas [2-4], which required a novel flowering-time adaptation. ZEA CENTRORADIALIS 8 (ZCN8) is the maize florigen gene and has a central role in mediating flowering [5, 6]. Here, we show that ZCN8 underlies a major quantitative trait locus (QTL) (qDTA8) for flowering time that was consistently detected in multiple maize-teosinte experimental populations. Through association analysis in a large diverse panel of maize inbred lines, we identified a SNP (SNP-1245) in the ZCN8 promoter that showed the strongest association with flowering time. SNP-1245 co-segregated with qDTA8 in maize-teosinte mapping populations. We demonstrate that SNP-1245 is associated with differential binding by the flowering activator ZmMADS1. SNP-1245 was a target of selection during early domestication, which drove the pre-existing early flowering allele to near fixation in maize. Interestingly, we detected an independent association block upstream of SNP-1245, wherein the early flowering allele that most likely originated from Zea mays ssp. mexicana introgressed into the early flowering haplotype of SNP-1245 and contributed to maize adaptation to northern high latitudes. Our study demonstrates how independent cis-regulatory variants at a gene can be selected at different evolutionary times for local adaptation, highlighting how complex cis-regulatory control mechanisms evolve. Finally, we propose a polygenic map for the pre-Columbian spread of maize throughout the Americas.
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http://dx.doi.org/10.1016/j.cub.2018.07.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6537595PMC
September 2018

A Gene for Genetic Background in Zea mays: Fine-Mapping enhancer of teosinte branched1.2 to a YABBY Class Transcription Factor.

Genetics 2016 Dec 11;204(4):1573-1585. Epub 2016 Oct 11.

Laboratory of Genetics, University of Wisconsin-Madison, Wisconsin 53706

The effects of an allelic substitution at a gene often depend critically on genetic background, i.e., the genotypes at other genes in the genome. During the domestication of maize from its wild ancestor (teosinte), an allelic substitution at teosinte branched (tb1) caused changes in both plant and ear architecture. The effects of tb1 on phenotype were shown to depend on multiple background loci, including one called enhancer of tb1.2 (etb1.2). We mapped etb1.2 to a YABBY class transcription factor (ZmYAB2.1) and showed that the maize alleles of ZmYAB2.1 are either expressed at a lower level than teosinte alleles or disrupted by insertions in the sequences. tb1 and etb1.2 interact epistatically to control the length of internodes within the maize ear, which affects how densely the kernels are packed on the ear. The interaction effect is also observed at the level of gene expression, with tb1 acting as a repressor of ZmYAB2.1 expression. Curiously, ZmYAB2.1 was previously identified as a candidate gene for another domestication trait in maize, nonshattering ears. Consistent with this proposed role, ZmYAB2.1 is expressed in a narrow band of cells in immature ears that appears to represent a vestigial abscission (shattering) zone. Expression in this band of cells may also underlie the effect on internode elongation. The identification of ZmYAB2.1 as a background factor interacting with tb1 is a first step toward a gene-level understanding of how tb1 and the background within which it works evolved in concert during maize domestication.
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http://dx.doi.org/10.1534/genetics.116.194928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5161286PMC
December 2016

Mapping Prolificacy QTL in Maize and Teosinte.

J Hered 2016 22;107(7):674-678. Epub 2016 Sep 22.

From the Life Science College, Shanxi Normal University, No. 1 Gongyuan Street, Linfen City, Shanxi Province 041004, China (L. Yang) and Laboratory of Genetics, University of Wisconsin-Madison, 425 Henry Mall, Madison, WI 53706 (C. J. Yang, Cheng, Xue, and Doebley).

Teosinte, the ancestor of maize, possesses multiple ears at each node along its main stalk, whereas maize has only a single ear at each node. With its greater ear number, teosinte is referred to as being more prolific. The grassy tillers 1 (gt1) gene has been identified as a large-effect quantitative trait locus underlying this prolificacy difference between maize and teosinte, and the causal polymorphism for the difference was mapped to a 2.7kb control region 5' of the gt1 ORF. The most common maize haplotype (M1) at the gt1 control region confers low prolificacy. A prior study reported that 29% of maize varieties possess the teosinte haplotype (T) for the control region, although these varieties are nonprolific. This observation suggested that these maize lines might possess an additional factor, other than gt1, suppressing prolificacy in maize. We discovered that the factor suppressing prolificacy in maize varieties with the gt1 T haplotype mapped to a 3.20 cM interval, which includes gt1 Subsequent DNA sequence analysis revealed that the maize varieties with the apparent T haplotype actually possess a distinct maize haplotype (M2) that is similar, but not identical, to the T haplotype in sequence but is associated with a nonprolific phenotype similar to the M1 haplotype. Our data indicate that the M2 haplotype or a closely linked factor confers a nonprolific phenotype. Our data suggest that 2 different alleles or haplotypes (M1 and M2) of gt1 were selected during domestication, and that nonprolificacy in all maize varieties is likely a result of allele substitutions at gt1.
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http://dx.doi.org/10.1093/jhered/esw064DOI Listing
July 2017
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