Literature DB >> 28469375

Numericware i: Identical by State Matrix Calculator.

Bongsong Kim1, William D Beavis1.   

Abstract

We introduce software, Numericware i, to compute identical by state (IBS) matrix based on genotypic data. Calculating an IBS matrix with a large dataset requires large computer memory and takes lengthy processing time. Numericware i addresses these challenges with 2 algorithmic methods: multithreading and forward chopping. The multithreading allows computational routines to concurrently run on multiple central processing unit (CPU) processors. The forward chopping addresses memory limitation by dividing a dataset into appropriately sized subsets. Numericware i allows calculation of the IBS matrix for a large genotypic dataset using a laptop or a desktop computer. For comparison with different software, we calculated genetic relationship matrices using Numericware i, SPAGeDi, and TASSEL with the same genotypic dataset. Numericware i calculates IBS coefficients between 0 and 2, whereas SPAGeDi and TASSEL produce different ranges of values including negative values. The Pearson correlation coefficient between the matrices from Numericware i and TASSEL was high at .9972, whereas SPAGeDi showed low correlation with Numericware i (.0505) and TASSEL (.0587). With a high-dimensional dataset of 500 entities by 10 000 000 SNPs, Numericware i spent 382 minutes using 19 CPU threads and 64 GB memory by dividing the dataset into 3 pieces, whereas SPAGeDi and TASSEL failed with the same dataset. Numericware i is freely available for Windows and Linux under CC-BY 4.0 license at https://figshare.com/s/f100f33a8857131eb2db.

Entities:  

Keywords:  Forward chopping; Genetic relationship matrix; Identical by state matrix; Multithreading; Numericware i

Year:  2017        PMID: 28469375      PMCID: PMC5395260          DOI: 10.1177/1176934316688663

Source DB:  PubMed          Journal:  Evol Bioinform Online        ISSN: 1176-9343            Impact factor:   1.625


Background

The inbreeding, identical by descent (synonymous to IBD, kinship, and coancestry), and identical by state (IBS) coefficients are central parameters in population genetics.[1] By definition, (1) the inbreeding coefficient refers to a proportion that a pair of alleles in an entity is identical in origin and state,[2] (2) the IBD coefficient between 2 entities equals twice the inbreeding coefficient for their virtual offspring,[3] and (3) the IBS coefficient between 2 entities equals twice a proportion that a pair of alleles in their virtual offspring is identical in state. The IBD matrix is a conventional indicator to represent genetic relationship among entities in a population, for which pedigrees are available. Emik and Terrill[3] suggested a systematic method for calculating a numerator relationship matrix (NRM) that displays IBD coefficients among every pair of entities in a population. Because the NRM is based on pedigrees, it represents genetic relationship from the genealogical perspective. High-throughput genotyping technologies provide abundant DNA profile that is useful to calculate the IBS matrix as a genetic relationship matrix. Some references[4],[5] introduced a method for computing the IBS matrix. Although the concept about the IBS matrix is general and simple, the IBS matrix is not widely used. Presumably, it might be due to the notoriously heavy computing burden. In this paper, we present software referred to as Numericware i. In order to deal with heavy workload, Numericware i supports parallelization and data management to avoid low memory.

Implementation

IBS coefficient

The IBS coefficients[4,5] can be calculated: where IBSA,B = the IBS coefficient between A and B; a1, a2 = a pair of chromosomes for A; b1, b2 = a pair of chromosomes for B; P(a1 ≡ b1) = the probability that a1 and b1 are homozygous; P(a1 ≡ b2) = the probability that a1 and b2 are homozy-gous; P(a2 ≡ b1) = the probability that a2 and b1 are homozygous; and P(a2 ≡ b2) = the probability that a2 and b2 are homozygous. The IBS coefficient for parents equals twice the homozygote coefficient (H) for their offspring. Thus, the H can be calculated: where C = the offspring of A and B; HC = the homozygote coefficient for C; a1, a2 = a pair of chromosomes for A; b1, b2 = a pair of chromosomes for B; P(a1 ≡ b1) = the probability that a1 and b1 are homozygous; P(a1 ≡ b2) = the probability that a1 and b2 are homozygous; P(a2 ≡ b1) = the probability that a2 and b1 are homozygous; and P(a2 ≡ b2) = the probability that a2 and b2 are homozygous. As the cost for producing genotypic data is becoming less expensive, the dimensions of genotypic datasets are rapidly growing. The amount of computing workload can be represented: where w = the amount of computational workload; n = the number of entities in a population; m = the number of markers. According to equation 3, the growing dimension of genotypic dataset causes 2 computational challenges: (1) lengthy computational time and (2) low memory.

Functionality of Numericware i

Numericware i, written in C++, has a simple user interface. The software provides 2 special functionalities: multithreading and forward chopping. The multithreading enables the computer to distribute the workload into multiple CPU threads. The forward chopping chops a dataset into multiple pieces that will not overextend memory capacity. Algorithm 1 shows the forward chopping algorithm. Algorithm 1. Forward Chopping algorithm. Numericware i provides users with more conveniences: Imputation not needed: The IBS computation is counting based. Numericware i skips counting missing genotypic data, assuming that the remaining genotypic data are of sufficiently large amount. IBS computation for a haplotype: This allows computation of the IBS matrix for a partial genomic block. Dataset integrity checking: This helps prevent a failure in the middle of analysis by checking the integrity of dataset at the beginning of work. Dataset summary: This provides users with overview of genotypic data. Supporting multiple types of datasets: This significantly reduces extra works for formatting the dataset. Numericware i accepts: alphanumeric, a pair of single-nucleotide polymorphisms (SNPs) and International Union of Pure and Applied Chemistry (IUPAC) formats. Transposing the dataset. Regarding item 5, details about dataset formats are described in the user manual, and example datasets are included in the software package. Numericware i completes the IBS matrix by copying the upper diagonals to the lower diagonals based on its symmetric property to reduce workload.

Application of the IBS matrix

Homozygote coefficient index

A diagonal value for an entity A in the IBS matrix implies the as , and IBSA,B represents twice the HC, in which C = the offspring of A and B. These principles can be useful in controlling homozygote level of progenies in a breeding program.

Best linear unbiased prediction

As a statistical model, the best linear unbiased prediction (BLUP)[6] is widely used to estimate breeding values. The BLUP requires the genetic relationship matrix, for which Henderson6 suggested using the NRM. The IBS matrix is superior to the NRM in the following aspects. First, the IBS matrix fully has values greater than 0, whereas the NRM includes an identity matrix for a base population. The identity matrix results in underestimation of IBD coefficients within the NRM. Second, the IBS matrix provides an objective measure based on genotypic data whereas the NRM is based on statistical expectation. As the BLUP expands to genome-wide association study and genomic prediction, the IBS matrix can apply to these studies.[7-11] The IBS matrix will be useful especially for plants since plant pedigrees are often unknown and imprecise.[12] Previous studies reported that the BLUP outperforms with genome-based genetic relationship matrices than the NRM.[13-18] In this context, the IBS matrix will be useful in improving the BLUP accuracy.

Results and Discussion

Negative effect of marker screen to IBS matrix

Marker collections generally consist of markers screened based on allele frequency. Marker screening secures allele diversity but causes an ascertainment bias in calculating the IBS matrix because the removed markers must be informative in representing the identical genomic state between entities. Thus, it is recommended to use all markers in calculating the IBS matrix.

Similarity between IBD and IBS

The IBD and IBS coefficients range between 0 and 2 in common. If it is assured that any identical alleles at the same locus from different entities were generated not independently but inherently, the IBS and IBD coefficients should be equal.[4] We hypothetically assume numerous unique mutations might inherently have flourished genetic diversity because the probability of the same mutations coincidentally occurring on the same loci of multiple genomes could be extremely low. If this assumption is true, the IBS and IBD matrices can be equal.

Comparison of results from Numericware i, SPAGeDi, and TASSEL

The IBS matrix can be expanded by computing the NRM based on pedigrees of entities within the IBS matrix. The expanded IBS matrix will have overall increased elemental values than the NRM solely based on pedigrees. The expansion of IBS matrix can be calculated using Numericware N.[19] Other popular software, SPAGeDi [20] and TASSEL,[8] implement different algorithms for calculating the genetic relationship matrix, causing their results to have different characteristics, such as negative values (SPAGeDi and TASSEL) or mono-diagonal values (SPAGeDi with 0’s). Thus, the resulting matrices from SPAGeDi and TASSEL cannot be expanded by the NRM algorithm. For comparison, we applied Numericware i, SPAGeDi, and TASSEL to the same dataset of 20 entities by 2000 SNPs (included in Supplementary file). The algorithms used by SPAGeDi and TASSEL are the ones by Loiselle et al[21] and Yang et al[22], respectively, and widely used for calculating the genetic relationship matrices.[7,23-26] Tables 1 to 3 are the resulting matrices. Pearson correlation coefficients among the 3 matrices (Table 4) indicate that the results from Numericware i and TASSEL are highly correlated at .9972, whereas the result from SPAGeDi shows low correlation coefficients with the results from Numericware i (0.0505) and TASSEL (0.0587). This illustrates that the results from Numericware i and TASSEL are substantially comparable, whereas SPAGeDi is not.
Table 1.

Identical by state matrix calculated using Numericware i.

ID1ID2ID3ID4ID5ID6ID7ID8ID9ID10ID11ID12ID13ID14ID15ID16ID17ID18ID19ID20
ID11.2530.485250.49350.50450.4930.49250.48650.49850.500250.5210.493750.475750.507750.4920.4940.51450.48650.506250.507750.49675
ID20.485251.25550.507750.492750.4970.506250.49050.5050.5040.505250.482250.49350.493750.5140.509250.4970.50150.485750.490250.4795
ID30.49350.507751.23650.510250.501750.491750.491750.499250.494750.506750.5050.503250.48350.497750.498750.505250.5020.506250.495750.499
ID40.50450.492750.510251.260.480750.484250.50250.487750.512250.504750.502250.493750.512250.5150.48550.50350.512750.50350.5110.48975
ID50.4930.4970.501750.480751.23650.480750.498250.509750.503250.5050.5060.5070.512750.4910.50650.50650.5060.5120.497750.51675
ID60.49250.506250.491750.484250.480751.2410.497250.491750.493250.50850.50.50650.502750.5090.509750.495750.4990.495750.487750.4845
ID70.48650.49050.491750.50250.498250.497251.2440.4940.509750.4890.484250.506750.49550.488250.5260.504250.49850.491250.4960.483
ID80.49850.5050.499250.487750.509750.491750.4941.26650.5030.50750.5070.507750.50150.499250.50050.491250.5030.504250.4850.50625
ID90.500250.5040.494750.512250.503250.493250.509750.5031.24350.508750.5010.499250.50350.514750.5040.498250.505250.483250.48850.49075
ID100.5210.505250.506750.504750.5050.50850.4890.50750.508751.250.491750.505250.506250.5070.487250.507250.499750.503750.501250.4765
ID110.493750.482250.5050.502250.5060.50.484250.5070.5010.491751.24850.4930.50150.5140.505250.50250.495250.511750.497750.5025
ID120.475750.49350.503250.493750.5070.50650.506750.507750.499250.505250.4931.2290.50050.48750.504750.514750.49950.498750.5150.49325
ID130.507750.493750.48350.512250.512750.502750.49550.50150.50350.506250.50150.50051.24450.50650.501750.507250.501250.51450.5110.484
ID140.4920.5140.497750.5150.4910.5090.488250.499250.514750.5070.5140.48750.50651.250.487750.5010.485250.510.5090.4595
ID150.4940.509250.498750.48550.50650.509750.5260.50050.5040.487250.505250.504750.501750.487751.23450.51350.49450.512750.5150.50525
ID160.51450.4970.505250.50350.50650.495750.504250.491250.498250.507250.50250.514750.507250.5010.51351.23350.487750.50150.512250.5005
ID170.48650.50150.5020.512750.5060.4990.49850.5030.505250.499750.495250.49950.501250.485250.49450.487751.2520.51550.49850.51
ID180.506250.485750.506250.50350.5120.495750.491250.504250.483250.503750.511750.498750.51450.510.512750.50150.51551.24450.50550.50175
ID190.507750.490250.495750.5110.497750.487750.4960.4850.48850.501250.497750.5150.5110.5090.5150.512250.49850.50551.2510.48925
ID200.496750.47950.4990.489750.516750.48450.4830.506250.490750.47650.50250.493250.4840.45950.505250.50050.510.501750.489251.244
Table 3.

Normalized identical by state matrix calculated based on the method of Yang et al. (2011) using TASSEL.

ID1ID2ID3ID4ID5ID6ID7ID8ID9ID10ID11ID12ID13ID14ID15ID16ID17ID18ID19ID20
ID10.990677−0.07475−0.07468−0.04347−0.07634−0.04866−0.07975−0.05198−0.049920.002185−0.03943−0.09083−0.02087−0.01028−0.07754−0.03706−0.0711−0.05719−0.04331−0.04571
ID2−0.074750.999107−0.02417−0.05987−0.0615−0.054−0.06972−0.0388−0.01471−0.055−0.0717−0.04805−0.08701−0.0283−0.04932−0.02896−0.04279−0.07973−0.07387−0.03686
ID3−0.07468−0.024170.933578−0.02535−0.04241−0.0831−0.07476−0.0629−0.05797−0.04924−0.02877−0.05716−0.0907−0.04558−0.05198−0.03182−0.04533−0.03638−0.03265−0.01861
ID4−0.04347−0.05987−0.025350.958366−0.10577−0.0528−0.04032−0.09919−0.00316−0.04468−0.06807−0.05746−0.0491−0.0297−0.07252−0.03923−0.01946−0.02074−0.03641−0.09108
ID5−0.07634−0.0615−0.04241−0.105770.953172−0.06293−0.02142−0.05554−0.03849−0.06151−0.03827−0.053−0.02515−0.06697−0.03413−0.07029−0.04079−0.03478−0.06206−0.00182
ID6−0.04866−0.054−0.0831−0.0528−0.062930.958312−0.02279−0.06428−0.05163−0.05079−0.03247−0.05604−0.05783−0.00742−0.02654−0.04114−0.06854−0.05117−0.07728−0.0489
ID7−0.07975−0.06972−0.07476−0.04032−0.02142−0.022790.9916−0.03756−0.0466−0.07431−0.06282−0.04842−0.0444−0.042760.0015−0.03824−0.05802−0.07736−0.07846−0.07538
ID8−0.05198−0.0388−0.0629−0.09919−0.05554−0.06428−0.037560.997001−0.05415−0.06069−0.03205−0.03071−0.03663−0.03451−0.05593−0.0677−0.04952−0.06389−0.06918−0.03179
ID9−0.04992−0.01471−0.05797−0.00316−0.03849−0.05163−0.0466−0.054150.952509−0.04427−0.07858−0.04378−0.01943−0.06021−0.05587−0.06662−0.03338−0.11517−0.05965−0.05892
ID100.002185−0.055−0.04924−0.04468−0.06151−0.05079−0.07431−0.06069−0.044270.980709−0.05307−0.05985−0.0829−0.02231−0.07237−0.05284−0.04877−0.04125−0.03556−0.07347
ID11−0.03943−0.0717−0.02877−0.06807−0.03827−0.03247−0.06282−0.03205−0.07858−0.053070.943432−0.0346−0.0497−0.0504−0.049−0.06394−0.05464−0.0468−0.07238−0.01673
ID12−0.09083−0.04805−0.05716−0.05746−0.053−0.05604−0.04842−0.03071−0.04378−0.05985−0.03460.955251−0.07892−0.0773−0.03479−0.03686−0.04771−0.06049−0.01148−0.02779
ID13−0.02087−0.08701−0.0907−0.0491−0.02515−0.05783−0.0444−0.03663−0.01943−0.0829−0.0497−0.078920.968834−0.03807−0.05919−0.06508−0.04826−0.03562−0.02503−0.05494
ID14−0.01028−0.0283−0.04558−0.0297−0.06697−0.00742−0.04276−0.03451−0.06021−0.02231−0.0504−0.0773−0.038070.931201−0.09514−0.02666−0.07504−0.05541−0.06462−0.10051
ID15−0.07754−0.04932−0.05198−0.07252−0.03413−0.026540.0015−0.05593−0.05587−0.07237−0.049−0.03479−0.05919−0.095140.953138−0.04718−0.05297−0.03786−0.0523−0.03
ID16−0.03706−0.02896−0.03182−0.03923−0.07029−0.04114−0.03824−0.0677−0.06662−0.05284−0.06394−0.03686−0.06508−0.02666−0.047180.945105−0.0886−0.03571−0.03108−0.07608
ID17−0.0711−0.04279−0.04533−0.01946−0.04079−0.06854−0.05802−0.04952−0.03338−0.04877−0.05464−0.04771−0.04826−0.07504−0.05297−0.08860.988198−0.05425−0.06342−0.02561
ID18−0.05719−0.07973−0.03638−0.02074−0.03478−0.05117−0.07736−0.06389−0.11517−0.04125−0.0468−0.06049−0.03562−0.05541−0.03786−0.03571−0.054250.975567−0.02854−0.04324
ID19−0.04331−0.07387−0.03265−0.03641−0.06206−0.07728−0.07846−0.06918−0.05965−0.03556−0.07238−0.01148−0.02503−0.06462−0.0523−0.03108−0.06342−0.028540.979937−0.06266
ID20−0.04571−0.03686−0.01861−0.09108−0.00182−0.0489−0.07538−0.03179−0.05892−0.07347−0.01673−0.02779−0.05494−0.10051−0.03−0.07608−0.02561−0.04324−0.062660.9201
Table 4.

Pearson correlation coefficients among results from Numericware i (Table 1), SPAGeDi (Table 2), and TASSEL (Table 3) for the same dataset.

Numericware iSPAGeDiTASSEL
Numericware i10.05050.9972
SPAGeDi0.050510.0587
TASSEL0.99720.05871
Identical by state matrix calculated using Numericware i. Genetic relationship matrix calculated based on the method of Loiselle et al. (1995) using SPAGeDi. Normalized identical by state matrix calculated based on the method of Yang et al. (2011) using TASSEL. Pearson correlation coefficients among results from Numericware i (Table 1), SPAGeDi (Table 2), and TASSEL (Table 3) for the same dataset.

Performance

In our test, Numericware i took 382 minutes in computing an IBS matrix with a simulated dataset of 500 entities by 10 000 000 SNPs using 19 CPU threads (Intel Xeon processor E5-2600 v4) and 64 GB memory. For this test, the whole dataset was chopped into 3 pieces to circumvent the low memory, whereas SPAGeDi and TASSEL failed with the same dataset due to the low memory.

Conclusions

The IBS matrix can be useful as: (1) a foreseeing index about the homozygote coefficients for hybrid lines based on the IBS coefficient for parents being equal to twice the homozygote coefficient for an offspring, (2) an assessment of homozygote coefficient to an entity itself based on IBSA,A being equal to 1 + HA, and (3) a component of the BLUP. Thus, Numericware i can be an essential tool for breeding. The multithreading and forward chopping reduce computing time and allow processing of extremely large amount of data. In contrast, other software are often limited by the physical memory size, and only a single CPU is supported. Numericware i is freely available for Windows and Linux under CC-BY 4.0 license and can be downloaded from https://figshare.com/s/f100f33a8857131eb2db.

Algorithm 1. Forward Chopping algorithm.

1:start_point = 0
2:for (j = 1; j <= num_pieces; j++){ // num_pieces = the total number of chopped pieces
3:if (j <= width % num_pieces) { // width = the total number of columns
4:chopped_width = ceil(width / num_pieces) // chopped_width = the width of a chopped piece
5:} else{
6:chopped_width = floor(width / num_pieces)
7:}
8:start_point = start_point + 1 // start_point = the first column coordinate of a chopped dataset
9:end_point = start_point + chopped_width - 1 // end_point = the last column coordinate of a chopped dataset
10:for (string line; getline(data, line)) {
11:count = 1
12:while (getline(line, temp, “,”)) {
13:if (count >= start_point) {
14:row.push_back(temp)
15:}
16:if (count == end_point) { break }
17: count++
18:}
19:table.push_back(row)
20:row.clear()
21:}
22://///////////////////////////////
23:IBS matrix computation with ‘table’
24://///////////////////////////////
25:table.clear()
26:start_point = end_point
27:}
Table 2.

Genetic relationship matrix calculated based on the method of Loiselle et al. (1995) using SPAGeDi.

ID1ID2ID3ID4ID5ID6ID7ID8ID9ID10ID11ID12ID13ID14ID15ID16ID17ID18ID19ID20
ID10−0.0068−0.00240.0039−0.004−0.0012−0.0053−0.00020.00120.0143−0.0027−0.01460.0053−0.0037−0.00430.0097−0.00790.00370.00620.0039
ID2−0.006800.0076−0.0039−0.0010.0084−0.00230.00440.0040.0038−0.0103−0.0023−0.00410.01160.0064−0.0020.0026−0.0101−0.0055−0.0077
ID3−0.00240.007600.00680.0011−0.0027−0.0027−0.0007−0.00350.00360.00410.0032−0.0122−0.0007−0.0020.00240.00170.0028−0.00290.0045
ID40.0039−0.00390.00680−0.0146−0.00910.0034−0.00980.00720.0010.0009−0.00460.00610.0098−0.0123−0.00010.0078−0.00040.0062−0.0031
ID5−0.004−0.0010.0011−0.01460−0.01150.00050.00520.0010.00120.00350.00450.0065−0.00660.0020.0020.00320.0054−0.00290.0153
ID6−0.00120.0084−0.0027−0.0091−0.011500.0029−0.004−0.00270.00660.00240.00720.00270.00880.0074−0.00230.0015−0.0026−0.0066−0.0036
ID7−0.0053−0.0023−0.00270.00340.00050.00290−0.00240.0086−0.0067−0.00830.0074−0.0022−0.00530.01850.00360.0011−0.0057−0.001−0.0046
ID8−0.00020.0044−0.0007−0.00980.0052−0.004−0.002400.00080.00290.00410.005−0.0012−0.0009−0.0021−0.00840.00110.0001−0.01160.0081
ID90.00120.004−0.00350.00720.001−0.00270.00860.000800.0040.0003−0.00060.00040.00990.0006−0.00340.0029−0.014−0.009−0.0022
ID100.01430.00380.00360.0010.00120.0066−0.00670.00290.0040−0.00710.00250.00120.0035−0.01190.0017−0.0019−0.0011−0.0013−0.013
ID11−0.0027−0.01030.00410.00090.00350.0024−0.00830.00410.0003−0.00710−0.0043−0.00040.00990.0020−0.00340.006−0.00210.0064
ID12−0.0146−0.00230.0032−0.00460.00450.00720.00740.005−0.00060.0025−0.00430−0.0008−0.00780.0020.0088−0.0001−0.00250.01010.0004
ID130.0053−0.0041−0.01220.00610.00650.0027−0.0022−0.00120.00040.0012−0.0004−0.000800.0032−0.0020.0017−0.00090.00630.0054−0.0079
ID14−0.00370.0116−0.00070.0098−0.00660.0088−0.0053−0.00090.00990.00350.0099−0.00780.00320−0.0098−0.0007−0.010.0050.0058−0.0228
ID15−0.00430.0064−0.002−0.01230.0020.00740.0185−0.00210.0006−0.01190.0020.002−0.002−0.009800.0058−0.00570.00490.0080.0065
ID160.0097−0.0020.0024−0.00010.002−0.00230.0036−0.0084−0.00340.001700.00880.0017−0.00070.00580−0.0103−0.00280.0060.0032
ID17−0.00790.00260.00170.00780.00320.00150.00110.00110.0029−0.0019−0.0034−0.0001−0.0009−0.01−0.0057−0.010300.0083−0.00190.0112
ID180.0037−0.01010.0028−0.00040.0054−0.0026−0.00570.0001−0.014−0.00110.006−0.00250.00630.0050.0049−0.00280.008300.00110.0037
ID190.0062−0.0055−0.00290.0062−0.0029−0.0066−0.001−0.0116−0.009−0.0013−0.00210.01010.00540.00580.0080.006−0.00190.00110−0.0034
ID200.0039−0.00770.0045−0.00310.0153−0.0036−0.00460.0081−0.0022−0.0130.00640.0004−0.0079−0.02280.00650.00320.01120.0037−0.00340
  19 in total

1.  Best linear unbiased estimation and prediction under a selection model.

Authors:  C R Henderson
Journal:  Biometrics       Date:  1975-06       Impact factor: 2.571

2.  TASSEL: software for association mapping of complex traits in diverse samples.

Authors:  Peter J Bradbury; Zhiwu Zhang; Dallas E Kroon; Terry M Casstevens; Yogesh Ramdoss; Edward S Buckler
Journal:  Bioinformatics       Date:  2007-06-22       Impact factor: 6.937

3.  Efficient methods to compute genomic predictions.

Authors:  P M VanRaden
Journal:  J Dairy Sci       Date:  2008-11       Impact factor: 4.034

4.  A relationship matrix including full pedigree and genomic information.

Authors:  A Legarra; I Aguilar; I Misztal
Journal:  J Dairy Sci       Date:  2009-09       Impact factor: 4.034

5.  GAPIT: genome association and prediction integrated tool.

Authors:  Alexander E Lipka; Feng Tian; Qishan Wang; Jason Peiffer; Meng Li; Peter J Bradbury; Michael A Gore; Edward S Buckler; Zhiwu Zhang
Journal:  Bioinformatics       Date:  2012-07-13       Impact factor: 6.937

6.  Variance of actual inbreeding.

Authors:  C C Cockerham; B S Weir
Journal:  Theor Popul Biol       Date:  1983-02       Impact factor: 1.570

7.  Common SNPs explain a large proportion of the heritability for human height.

Authors:  Jian Yang; Beben Benyamin; Brian P McEvoy; Scott Gordon; Anjali K Henders; Dale R Nyholt; Pamela A Madden; Andrew C Heath; Nicholas G Martin; Grant W Montgomery; Michael E Goddard; Peter M Visscher
Journal:  Nat Genet       Date:  2010-06-20       Impact factor: 38.330

8.  Genome-wide association study for grain yield and related traits in an elite spring wheat population grown in temperate irrigated environments.

Authors:  Sivakumar Sukumaran; Susanne Dreisigacker; Marta Lopes; Perla Chavez; Matthew P Reynolds
Journal:  Theor Appl Genet       Date:  2014-12-10       Impact factor: 5.699

9.  Association mapping for important agronomic traits in core collection of rice (Oryza sativa L.) with SSR markers.

Authors:  Peng Zhang; Xiangdong Liu; Hanhua Tong; Yonggen Lu; Jinquan Li
Journal:  PLoS One       Date:  2014-10-31       Impact factor: 3.240

10.  Genome-wide association study identifies multiple susceptibility loci for pulmonary fibrosis.

Authors:  Tasha E Fingerlin; Elissa Murphy; Weiming Zhang; Anna L Peljto; Kevin K Brown; Mark P Steele; James E Loyd; Gregory P Cosgrove; David Lynch; Steve Groshong; Harold R Collard; Paul J Wolters; Williamson Z Bradford; Karl Kossen; Scott D Seiwert; Roland M du Bois; Christine Kim Garcia; Megan S Devine; Gunnar Gudmundsson; Helgi J Isaksson; Naftali Kaminski; Yingze Zhang; Kevin F Gibson; Lisa H Lancaster; Joy D Cogan; Wendi R Mason; Toby M Maher; Philip L Molyneaux; Athol U Wells; Miriam F Moffatt; Moises Selman; Annie Pardo; Dong Soon Kim; James D Crapo; Barry J Make; Elizabeth A Regan; Dinesha S Walek; Jerry J Daniel; Yoichiro Kamatani; Diana Zelenika; Keith Smith; David McKean; Brent S Pedersen; Janet Talbert; Raven N Kidd; Cheryl R Markin; Kenneth B Beckman; Mark Lathrop; Marvin I Schwarz; David A Schwartz
Journal:  Nat Genet       Date:  2013-04-14       Impact factor: 38.330

View more
  3 in total

1.  Classifying Oryza sativa accessions into Indica and Japonica using logistic regression model with phenotypic data.

Authors:  Bongsong Kim
Journal:  PeerJ       Date:  2019-11-07       Impact factor: 2.984

2.  Linkage disequilibrium and population structure in a core collection of Brassica napus (L.).

Authors:  Mukhlesur Rahman; Ahasanul Hoque; Jayanta Roy
Journal:  PLoS One       Date:  2022-03-01       Impact factor: 3.240

3.  Genetic diversity analysis of a flax (Linum usitatissimum L.) global collection.

Authors:  Ahasanul Hoque; Jason D Fiedler; Mukhlesur Rahman
Journal:  BMC Genomics       Date:  2020-08-14       Impact factor: 3.969

  3 in total

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