<b>Production and characterization of amphidiploids from hybrids between </b><b><i>Arachis ipaënsis</i></b> <b>and </b><b><i>A. duranensis </i></b><b>(Fabaceae): implications for peanut improvement</b>

Background and aims: Arachis hypogaea is an allotetraploid species of global economic importance; however, its narrow genetic base renders it vulnerable to pests and diseases. In contrast, wild diploid Arachis species possess valuable resistance alleles, but ploidy differences limit their direct use in breeding. Syntheticamphidiploids overcome this barrier, however, BBAA amphidiploids compatible with peanut are not available in Argentina. This study aimed to develop amphidiploidindividuals suitable for national pre-breeding efforts. M&M: Two chromosome duplication protocols were evaluated in hybrids [A. ipaënsis × A. duranensis]2x based on partial or complete immersion of cuttings in a 0.2 % colchicine solution. Ploidy level was verified by flow cytometry and genome composition was confirmed by DAPI banding. Pollen viability was estimated via acetocarmine staining. Fruit characterization was performed using Fiji software. Results: Flow cytometry confirmed that only protocol II yielded tetraploid individuals. DAPI banding revealed the expected BBAA genome configuration, and restoredfertility was demonstrated by high pollen viability and fruit production. Morphologically, amphidiploids showed vigorous growth and increased fruit size. Conclusions: Fertile BBAA amphidiploids were developed as a strategic resource for peanut pre- reeding in Argentina. Additionally, it will support studies on polyploid genome stabilization, and trait expression following hybridization and chromosome duplication in Arachis.