Scientists Clash Over DNA Paternity Testing in Citronella Breeding Programs

A scientific dispute has surfaced in the pages of Molecular Biology Reports, where researchers from CSIR-Central Institute of Medicinal and Aromatic Plants in Bangalore have published a formal rebuttal to a paper on SSR-based paternity analysis in citronella polycross breeding. The correspondence, authored by Keerthi Biradar, S. Gazala Parveen, and corresponding author Channayya Hiremath, appeared on 16 October 2026, the same day the original article went live, signaling an unusually rapid and pointed exchange between research groups working on the same crop.

Citronella grass, a member of the aromatic genus Cymbopogon, is the source of citronella oil, one of the most widely used natural insect repellents and fragrance ingredients in the world. The crop is cultivated across tropical Asia, Africa, and the Americas, and its commercial value depends heavily on the quality and yield of the essential oil extracted from its leaves. Improving citronella through breeding is therefore an ongoing priority for institutes across India and other producing countries, and the genetics of the crop presents distinctive challenges that make the current dispute more than an academic squabble.

At the heart of the debate lies a technique known as paternity analysis using simple sequence repeat markers, or SSRs. SSRs, also called microsatellites, are short stretches of DNA in which a motif of two to six base pairs repeats over and over. Because the number of repeats at a given locus often varies between individuals, these markers are highly polymorphic, cheap to assay through polymerase chain reaction, and codominant, meaning that breeders can distinguish homozygotes from heterozygotes at each locus. Those properties make SSRs a workhorse of plant genetics, used for fingerprinting varieties, constructing genetic maps, tagging quantitative trait loci, and, critically for this dispute, assigning parentage in controlled crosses.

Paternity analysis becomes essential in polycross breeding designs. A polycross is a nursery in which several selected parent plants are grown together and allowed to intermate freely through wind or insect pollination. The approach is standard for crops that are clonally propagated, self-incompatible, or otherwise difficult to cross in a controlled, pairwise fashion. Citronella fits this profile well: it is a sterile or near-sterile, outcrossing, vegetatively propagated grass in which deliberate hybridization is laborious. By planting candidate parents together and later using molecular markers to determine which plant actually sired each offspring, breeders can estimate the combining ability of each parent without ever performing a single hand pollination. The offspring that inherit the best combination of alleles can then be cloned and advanced through selection.

The catch is that the statistical machinery behind paternity assignment rests on assumptions that are easy to state and hard to verify. The method requires that the candidate parents carry sufficiently different SSR profiles, that allele frequencies in the surrounding population are known, that genotyping errors are negligible, and that all possible fathers have been sampled. When related parents share alleles by descent, when null alleles cause heterozygotes to be misread as homozygotes, or when mutation or allele dropout corrupts the raw data, the probability of assigning a seedling to the wrong father rises sharply. Exclusion probabilities that look impressive on paper can collapse in practice, and likelihood-based assignment methods can quietly favor one parent over another for reasons that have nothing to do with true parentage.

These pitfalls are precisely the kind of territory that a rebuttal in a molecular biology journal typically addresses. Correspondence pieces of this sort generally challenge the methodology, interpretation, or novelty of an earlier paper, and the rapid turnaround in this case suggests the Bangalore group felt the issues warranted immediate public attention. The original article, titled on the progress made and the remaining challenges in applying SSR markers to citronella polycross breeding, evidently made claims or recommendations that Biradar and colleagues judged significant enough to contest formally rather than in private correspondence with the authors or the editors.

For readers outside plant breeding, the stakes may seem narrow, but the implications ripple outward. Marker-based paternity analysis is increasingly central to breeding programs for a long list of perennial and clonally propagated crops, from forage grasses and eucalyptus to fruit trees and aromatic plants like citronella. India’s CSIR network of institutes maintains extensive germplasm collections of medicinal and aromatic species, and the Research Centre in Bangalore, where all three rebuttal authors are affiliated, specializes in plant breeding and genetic resource conservation. Methodological disagreements about how to interpret SSR data in polycross nurseries therefore touch on how public breeding programs across the tropics will select the next generation of oil-yielding cultivars.

The broader context is a transition now underway in crop genetics. SSR markers, once the default choice for fingerprinting and parentage work, are being supplemented and in some settings replaced by single nucleotide polymorphism arrays and genotyping-by-sequencing approaches, which deliver thousands of markers instead of dozens and reduce the sampling error that plagues small marker panels. Yet SSRs remain attractive for laboratories with limited budgets, particularly in developing-country institutes, because they require no reference genome, no bioinformatics pipeline, and only basic capillary electrophoresis equipment. Whether the remaining challenges in citronella paternity analysis are best solved by refining SSR protocols or by migrating to denser marker systems is exactly the sort of question such rebuttals are meant to sharpen.

Scientific rebuttals also serve a quieter institutional function. Journals such as Molecular Biology Reports publish correspondence to create a permanent, citable record of disagreement, allowing the original authors to respond and the community to weigh the arguments on their merits. The fact that both the original article and the rebuttal carry the same publication date of 16 October 2026 indicates the editors coordinated the release, a practice that ensures readers encounter the critique alongside the work it addresses rather than months later. The rebuttal is listed as volume 53, article number 1747 of the journal, with the original article available under a separate DOI.

What happens next will follow the well-worn path of scientific self-correction. The authors of the original paper may respond in kind, the two groups may find common ground in a revised protocol, or the dispute may simply stand as a cautionary marker for breeders tempted to over-interpret paternity assignments from limited marker data. For citronella growers and the fragrance and repellent industries that depend on the crop, the outcome matters in a concrete way: faster, more reliable breeding depends on molecular tools that breeders can trust. The exchange in Molecular Biology Reports is a reminder that behind every improved cultivar lies not just greenhouse work and field trials, but rigorous, sometimes contentious, argument about what the DNA data actually mean.

Subject of Research: SSR marker-based paternity analysis in citronella polycross breeding

Article Title: Rebuttal on “SSR-based paternity analysis in citronella polycross breeding: progress and remaining challenges”

Article References: Biradar, K., Parveen, S. G., & Hiremath, C. (2026). Rebuttal on “SSR-based paternity analysis in citronella polycross breeding: progress and remaining challenges”. Molecular Biology Reports, 53(1), Article 1747. https://doi.org/10.1007/s11033-026-12898-1

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12898-1

Keywords: citronella, SSR markers, microsatellites, paternity analysis, polycross breeding, plant genetics, Cymbopogon, molecular markers, plant breeding, Molecular Biology Reports, CSIR-CIMAP, genetic markers