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The hybrid lethality of interspecific F1 hybrids of Nicotiana: a clue to understanding hybrid inviability—a major obstacle to wide hybridization and introgression breeding of plants


Reproductive isolation poses a major obstacle to wide hybridization and introgression breeding of plants. Hybrid inviability in the postzygotic isolation barrier inevitably reduces hybrid fitness, consequently causing hindrances in the establishment of novel genotypes from the hybrids among genetically divergent parents. The idea that the plant immune system is involved in the hybrid problem is applicable to the intra- and/or interspecific hybrids of many different taxa. The lethality characteristics and expression profile of genes associated with the hypersensitive response of the hybrids, along with the suppression of causative genes, support the deleterious epistatic interaction of parental NB-LRR protein genes, resulting in aberrant hyper-immunity reactions in the hybrid. Moreover, the cellular, physiological, and biochemical reactions observed in hybrid cells also corroborate this hypothesis. However, the difference in genetic backgrounds of the respective hybrids may contribute to variations in lethality phenotypes among the parental species combinations. The mixed state in parental components of the chaperone complex (HSP90-SGT1-RAR1) in the hybrid may also affect the hybrid inviability. This review article discusses the facts and hypothesis regarding hybrid inviability, alongside the findings of studies on the hybrid lethality of interspecific hybrids of the genus Nicotiana. A possible solution for averting the hybrid problem has also been scrutinized with the aim of improving the wide hybridization and introgression breeding program in plants.

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Cleaved amplified polymorphic sequence

CHORD1and 2:

Cysteine- and histidine-rich domain 1 and 2


Clustered regularly interspaced short palindromic repeats-Cas9


CHORD-containing protein and SGT1 domain


Enhanced disease susceptibility 1


Heat shock protein 90

NB-LRR protein:

Nucleotide-binding site and leucine-rich repeat protein

NLR protein:

NB and LRR–containing protein


Nucleotide-binding domain


Required for Mla 12 resistance


SGT1-specific domain


Suppressor of G2 allele of Skp1


Simple sequence repeats


Tetratricopeptide repeat


Virus-induced gene silencing


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We are indebted to Mr. Takumi Yamamoto for his contribution to collect a part of the data in Fig. 3. This study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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Masanobu Mino, the corresponding author, certifies that all authors have participated sufficiently in preparing the manuscript. Masanobu Mino gave the basic idea for the article, performed the literature search, wrote manuscript, and reviewed and edited the manuscript. Takahiro Tezuka proposed ideas for improving the quality of the article and reviewed and edited the manuscript. Sachiko Shomura performed the experiments, collected and analyzed the data in Figs. 2 and 3, and reviewed the manuscript.

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Correspondence to Masanobu Mino.

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Appendix 1

Table 1

Table 1 Phenotypes of five lethality observed in interspecific F1 hybrid of genus Nicotiana

Appendix 2

  1. 1.

    Cell culture and determination of cell viability

    After 3 to 4 days of subculture in fresh liquid medium, the cells were transferred to 26 ºC or 37 ºC, and their viability was determined by a previously reported method (Mino et al. 2005).

  2. 2.

    Cellular treatment

    The pharmacological treatments of the cells were performed 0.5 h before transferring the cells from 37 ºC to 26 ºC. Cell viability was determined 3 h following the temperature shift. Moreover, to explore the effects of calcium ion (Ca2+), the cells were cultured for 10 days in the calcium-free medium to reduce intracellular Ca2+ concentration. The concentration of each reagent treatment was as follows: okadaic acid (OkA), 0.1 μM; calyculin A (CA), 0.1 μM; staurospolin (ST), 1 μM; U0126, 100 μM; mastoparan (MP), 5 μM; gadolinium chloride (GD), 5 μM; ruthenium red (Rred), 50 mM; ethylene glycol tetraacetic acid (EGTA), 1 mM; CaCl2 (Ca), 1 mM; and neomycine (Neo), 100 μM.

  3. 3.


    The percentage data were transformed into arcsine values to calculate the standard error (SE) of the mean. Differences between the means were analyzed using the Mann-Whitney U test at a 5% level of significance.

    Mino M et al. (2005) Plant Cell Rep 24:179–188.

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Mino, M., Tezuka, T. & Shomura, S. The hybrid lethality of interspecific F1 hybrids of Nicotiana: a clue to understanding hybrid inviability—a major obstacle to wide hybridization and introgression breeding of plants. Mol Breeding 42, 10 (2022).

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  • Plant breeding
  • Wide hybridization
  • Nicotiana species
  • Hybrid inviability
  • Plant immune system
  • Chaperone complex