Androgenesis and Embryogenesis in Rice: Mechanisms, Biotechnological Applications, and Breeding Prospects
P. Sharmela *
Guest Faculty, School of Agriculture and Animal Sciences, The Gandhigram Rural Institute, Dindigul – 624302 Tamil Nadu, India.
M. Chithra
Guest Faculty, School of Agriculture and Animal Sciences, The Gandhigram Rural Institute, Dindigul – 624302 Tamil Nadu, India.
M. Arun Kumar
JSA College of Agriculture and technology, Avatti, Cuddalore - 606108 Tamil Nadu, India.
*Author to whom correspondence should be addressed.
Abstract
Rice improvement increasingly depends on the rapid generation of homozygous lines and on a deeper understanding of the cellular pathways that govern embryo formation, whether from gametes, somatic tissue, or engineered reproductive systems. Androgenesis, the redirection of the male gametophyte towards a sporophytic, embryogenic fate, has underpinned doubled haploid breeding in rice for more than five decades, yet its practical value remains constrained by strong genotype dependence, persistent albinism among regenerated plantlets, and the comparative recalcitrance of indica backgrounds relative to japonica. Parallel advances in the molecular dissection of embryogenesis, particularly the elucidation of the BABY BOOM–auxin module governing zygotic and somatic embryo initiation and the identification of phospholipase genes and gamete-fusion-associated DMP genes that contribute to in vivo haploid induction, have opened a second, genetically tractable route to haploid and doubled haploid production that largely bypasses tissue culture. This review traces the cellular, physiological and molecular basis of androgenesis and embryogenesis in rice, critically appraises the principal in vitro and in vivo platforms used to generate haploid and doubled haploid material, and evaluates how these technologies intersect with contemporary efforts to engineer synthetic apomixis for the fixation of hybrid vigour. Particular attention is given to the comparative efficiency, fertility costs, and genomic stability of competing haploid-induction strategies, to the persistent biological barriers that limit indica responsiveness, and to the breeding outcomes—ranging from quantitative trait locus mapping populations to improved parental and restorer lines—that these technologies have enabled. The review concludes that, while in vitro androgenesis remains an indispensable tool for several rice breeding programmes, the convergence of haploid-inducer genetics, genome editing, and embryogenic trigger genes is reshaping the field towards genotype-independent, in vivo systems whose translation into widely deployable commercial technology will depend on resolving trade-offs between induction frequency, seed fertility, and regulatory acceptance.
Keywords: Androgenesis, anther culture, doubled haploid, embryogenesis, haploid induction, rice breeding, synthetic apomixis