Understanding and overcoming hybrid lethality in seed and seedling stages as barriers to hybridization and gene flow

Abstract

Hybrid lethality is a type of reproductive isolation barrier observed in two developmental stages, hybrid embryos (hybrid seeds) and hybrid seedlings. Hybrid lethality has been reported in many plant species and limits distant hybridization breeding including interspecific and intergeneric hybridization, which increases genetic diversity and contributes to produce new germplasm for agricultural purposes. Recent studies have provided molecular and genetic evidence suggesting that underlying causes of hybrid lethality involve epistatic interaction of one or more loci, as hypothesized by the Bateson–Dobzhansky–Muller model, and effective ploidy or endosperm balance number. In this review, we focus on the similarities and differences between hybrid seed lethality and hybrid seedling lethality, as well as methods of recovering seed/seedling activity to circumvent hybrid lethality. Current knowledge summarized in our article will provides new insights into the mechanisms of hybrid lethality and effective methods for circumventing hybrid lethality.

Molecular basis and evolutionary drivers of endosperm-based hybridization barriers

“…Recent advances in the field of evolutionary biology have recognized postzygotic mechanisms as substantial drivers of plant speciation ( Coughlan 2023 ). These mechanisms operate at various time points after fertilization, leading to impaired viability of hybrid seeds or seedlings or sterility of the resulting hybrids ( He et al 2023 ). In this review, we focus on the evolution of postzygotic barriers arising from the endosperm, particularly in the context of interspecies and interploidy hybridizations.…”

Genetic Cause of Hybrid Lethality Observed in Reciprocal Interspecific Crosses between Nicotiana simulans and N. tabacum

“…A typical example of postmating-prezygotic barriers is the cross-incompatibility between pollen and pistils [4][5][6][7][8][9][10][11]. Postzygotic barriers include hybrid seed abortion [4,, hybrid weaknesses [37][38][39][40][41][42][43][44][45][46][47], hybrid lethality [32,[48][49][50][51][52][53][54][55][56][57][58][59][60] or necrosis [61][62][63][64][65][66][67][68][69][70][71], and hybrid sterility [72][73][74][75][76]…”

“…Postzygotic barriers include hybrid seed abortion [4,, hybrid weaknesses [37][38][39][40][41][42][43][44][45][46][47], hybrid lethality [32,[48][49][50][51][52][53][54][55][56][57][58][59][60] or necrosis [61][62][63][64][65][66][67][68][69][70][71], and hybrid sterility [72][73][74][75][76][77][78][79] in plants of the F 1 generation, and hybrid breakdown is expressed as weaknesses, lethality, or sterility in plants of F 2 or later generations [49,[80][81][82][83]…”