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Description

Many bisexual flowers exhibit the occurrence of non-functional pollen alongside fully fertile ovules. Various natural mechanisms prevent self-fertilization to promote diversity and variability. Hermaphroditic species often exhibit genetic male-sterility that retain normal female functions, with diverse phenotypic manifestations. This can be due to environment-sensitive nuclear male sterility (MS) controlled by nuclear genes and influenced by environmental conditions, or cytoplasmic MS, determined by the mitochondrial genome and suppressed by nuclear restorer genes. Another mechanism, self-incompatibility (SI), found in many angiosperms and fungi, promotes cross-fertilization and prevents inbreeding. This involves self-recognition interactions between haploid and diploid genomes and categorized as either gametophytic or sporophytic SI. Since their discovery, these phenomena have been extensively applied to facilitate hybridization. Hybrid breeding exploits heterosis which combines complementary genes from both parents, resulting in high-performance traits. Male sterility and SI systems enable controlled pollination during large-scale seed production; however, their application is constrained by factors such as environmental instability, incomplete fertility restoration, and dependence on specific restorer genotypes. Despite these limitations, the strategic deployment of male sterility and self-incompatibility systems has profoundly advanced hybrid breeding technologies and remains central to modern plant breeding and agricultural productivity.