SSR-based paternity analysis in citronella polycross breeding: progress and remaining challenges

Polycross breeding offers a promising strategy to introduce genetic variation in clonally propagated crops such as citronella (Cymbopogon winterianus), where limited genetic diversity constrains breeding progress. Biradar and colleagues recently employed SSR markers to identify pollen donors among half‑sib progenies from four commercial cultivars, reporting identification of potential paternal parents for five of eleven progenies. Three methodological considerations warrant careful attention. First, the paternity assignment success rate (45%) is substantially lower than the 79-99% recovery rates routinely achieved in polycross studies, reflecting insufficient marker number, limited informativeness (PIC = 0.33), and the use of simple exclusion without likelihood‑based confidence estimation. Second, the open‑field design without pollen contamination assessment leaves a critical gap in validity, given documented contamination rates up to 36% in similar systems. Third, identification of "superior" progenies based on single‑harvest performance is undermined by substantial declines (up to 30%) observed in the second harvest. Until these methodological gaps are addressed, the evidence for successful paternity identification and population improvement in citronella remains preliminary.