Effect of genotype, media and stress treatments on gynogenesis efficiency in short-day tropical Indian onion (Allium cepa L.)

Gynogenesis plays a crucial role in creating homozygous lines and accelerates the breeding process. This technique has been the subject of investigation in onion for several decades. But achieving desired efficiency levels, an effective diploidization protocol and a high survival rate of doubled haploids is still a limiting factor. Further, research on short-day onions, which occupy a major share in production, is still inadequate compared to long-day onions. This study investigated the gynogenic response of ten short-day onion genotypes, using whole flower buds, cultured on MS and B5 medium supplemented with different growth regulators and stress treatments. ‘Bhima Safed’ (9.52%) and ‘Bhima Dark Red’ (9.14%) recorded the highest gynogenesis efficiency. ‘Early Grano’ did not respond to gynogenesis indicating its recalcitrant nature. Among media, OGH8 (MS medium supplemented with 2 mg/l 2,4-D and 2 mg/l BAP) was found superior to OGH4 (B5 medium supplemented with 2 mg/l 2,4-D and 2 mg/l BAP) and 0MS (MS medium without growth regulators) in inducing gynogenesis. Cold pretreatment of flower buds for 2 days in Bhima Dark Red (7.33%) was superior to control (6.67%). Heat treatment of flower buds was not favourable for gynogenesis induction. The induced embryos were studied for root induction. RMS1 (16.86) and RMS2 (10.14) recorded the highest number of roots, while RMS5 (4.86) exhibited the highest propensity for shoot formation, ultimately resulting in the successful regeneration of whole plants. 51.39% of the induced plants were haploid, 26.39% spontaneous diploid, and 22.22% mixoploid. For diploidization, treatment of 500 μM colchicine for 4 h was superior with a 75% survival rate. Doubled haploid plants were cultured on the MS medium for bulbil induction. These bulbils were transferred under field conditions for flowering and seed production. This study presents a comprehensive strategy for gynogenesis induction and will be of benefit to onion researchers.Key message: This paper gives a comprehensive strategy of doubled haploid production from genotype selection, haploid induction, doubled haploids acclimatization to flowering, for the first time in short-day tropical Indian onions. [ABSTRACT FROM AUTHOR]