Luc Janss
ljanss.bsky.social
Luc Janss
@ljanss.bsky.social
Plant breeding and genetics, big data, prediction, spanning from functional genomics to satellitte images, professor at Aarhus University, Denmark
Presented on the frontiers of genomic prediction for #PlantBreeding at the 8th Cereal Biotennology and Breeding conference in Budapest, and got some traction on X!
November 13, 2025 at 12:48 PM
Good point. Collecting the data often need many years, hours and $$$, it adds another irony to use a quick & dirty method for analysis. Machine learners are proud to spend thousands of hours HPC time for an analysis, biologist are proud if they can do an analysis in 30 secs on their laptop.
Haseman-Elston regression is bit of an irony for massive biobanks because it throws away the statistical precision that was gained by accounting for more samples. You might be able to analyze more data, but you don't get more information out of it.
November 12, 2025 at 9:25 AM
No, you will not triple yield by tripling the number of grains per spike 👇
November 5, 2025 at 8:38 AM
Reposted by Luc Janss
1/ If you're in bioinformatics, you're staring at matrices all day.
RNA-seq? Gene x sample.
scRNA-seq? Gene x cell.
Everything is a matrix.
But I never learned how to think in matrices. And I regret it.
October 23, 2025 at 1:45 PM
Confused about vector resize() and reserve() in #C++? Resize modifies the size and fills default values; after resize'ing use [] to fill elements. Reserve only reserves memory in the background but size remains zero; after reserve use push_back to fill the vector. Don't confuse these two!
October 22, 2025 at 12:44 PM
Somebody has fenced off and seems to claim chromosome X. Elon? 🤣
September 12, 2025 at 8:05 AM
And another touch of geniality: he used observable Mendelian traits (colors on the seeds) as markers to map the
quantitative trait, and understood it needs a cross to prove genetic linkage. It's gene mapping using biparental families in a rudimentary form.
This always blows my mind. Dude mapped qtl for a quantitative trait to a chromosome in 1923!
Related but cool combo of cytogenetics and phenotype. Know when the first QTL was mapped?

Sax, K. 1923. The association of size differences with seed coat pattern and pigmentation in Phaseolus vulgaris. Genetics 8:552-560.
August 27, 2025 at 8:02 AM
Teaching on additive, dominance, epistatic, transcriptomic, environmental (and more) relationship matrices, it occurs that the VanRaden GRMs are an exception with a sum(2pq) scaling, whereas all others are simply scaled to average diagonal 1. Can't we just scale all 'kernels' to mean diagonal 1?
August 8, 2025 at 7:16 AM
Reposted by Luc Janss
👇A very needed paper and discussion: genomic and phenomic prediction should not be compared, and suggesting that better phenotype prediction will improve breeding is misleading. Phenotypes include environment, but breeders don't sell environment (let that sink in 🤔🙂).
🌱 Accuracy stats alone can be misleading: phenomic vs. genomic prediction models require full breeder’s equation analysis to compare real-world value. (Fangyi Wang, Mitchell J Feldmann, Daniel E Runcie)
▶️ www.biorxiv.org/content/10.1...
#PlantScience #PlantBreeding #genomics #phenomics
June 7, 2025 at 5:14 PM
On the domestication of maize (aka corn) with @jrossibarra.bsky.social (a podcast) 👇
Talking Biotech 459 - where did the key domestication mutations in corn come from? Were they present in resident gene pools waiting to be selected, or new mutations? I discuss with @jrossibarra and his student Regina Fairbanks.
@aspb @ASHS_Hort @UF_IFAS share.transistor.fm/s/bed2ffa6
May 25, 2025 at 7:51 AM
Can recommend both the conference and the city 👇
Please share: Registration is now open for EUCARPIA Biometrics in Plant Breeding 2025 highlanderlab.github.io/EUCARPIA2025...
May 8, 2025 at 5:31 PM
We know GBLUP prediction accuracy gets worse for more distant generations (implying SNP effects changing!). In my teaching I explain it's long-range LD (from selection and family structure) breaking down. This nice article substantiates this more properly: doi.org/10.1186/s127...
Erosion of estimated genomic breeding values with generations is due to long distance associations between markers and QTL - Genetics Selection Evolution
Background Most validation studies of genomic evaluations on candidates (prior to observing phenotypes) present inflation of their predicted breeding values, i.e., regression coefficients of their lat...
doi.org
May 7, 2025 at 8:52 AM
This professor position can fit any candidates working on genomic tools to address resilience, sustainability, climate adaptation or biodiversity in agriculture 👇
April 2, 2025 at 10:19 AM
Our summer course on #genomicPrediction with me and @guillramstein.bsky.social is running this year 4-8 August, application deadline 18 March. Info and registration see: international.au.dk/education/ad...
March 9, 2025 at 1:00 PM
Interesting work on combining distantly related populations aka closely related species 👇
January 25, 2025 at 7:27 PM
From "X":
New article out by Marta Malinowska et al., including a small gene mapping using our Bayesian mapping tools - soon to be released (keep watching bsky 😉): Automated seminal root angle measurement with corrective annotation 🌱 : doi.org/10.1093/aobp...
#PlantBreeding #Automation #Phenotyping
Automated seminal root angle measurement with corrective annotation
Abstract. Measuring seminal root angle is an important aspect of root phenotyping, yet automated methods are lacking. We introduce SeminalRootAngle, a nove
doi.org
November 22, 2024 at 9:13 AM