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<p>The interaction of the tomato <i>Mi</i>-1.2 gene with the members of the genus <i>Meloidogyne</i> is a special case where a single host factor confers resistance to an array of up to 13 species, but not against <i>M. enterolobii</i> populations. There are numerous reports of “defeated” resistance genes in distinct pathosystems, which are not effective against distinct pathogen variants (at biotype, race, or species level as in the case of the <i>Mi</i>-1.2 gene). However, a subgroup of these apparently non-effective genes can still display residual or “ghost” effects, resulting in lower damage levels caused by a virulent pathogen. Thus far, residual effects of the <i>Mi</i>-1.2 gene to <i>M. enterolobii</i> have not been properly investigated. Herein, two comparative assays using contrasting near-isogenic lines (NILs) for presence/absence of the <i>Mi</i>-1.2 locus were carried out using a guava race population of <i>M. enterolobii</i>. Seedlings of two pairs of contrasting NILs ‘Nemadoro’ (homozygous dominant; <i>Mi</i>-1.2/<i>Mi</i>-1.2) / ‘Rio Grande’ (homozygous recessive, <i>mi</i>-1.2/<i>mi</i>-1.2) and ‘Del Rey’ (<i>Mi</i>-1.2/<i>Mi</i>-1.2) / ‘Calipso’ (<i>mi</i>-1.2/<i>mi</i>-1.2) were inoculated with 2,000&#xa0;M<i>. enterolobii</i> eggs. The homozygous dominant (<i>Mi</i>-1.2/<i>Mi</i>-1.2) NILs displayed values for the quantitative parameter number of eggs + J2s per gram of root tissue similar or even superior to their corresponding recessive (<i>mi</i>-1.2/<i>mi</i>-1.2) NILs. A slight positive impact of the resistance gene in the reproduction factor (RF) value was observed only for one pair of contrasting NILs (‘Del Rey’ / ‘Calipso’), which was restricted to one bioassay. Hence, the employment of NILs in our bioassays allowed us to hypothesize that the <i>Mi</i>-1.2 gene, although extremely effective against populations of at least 13 <i>Meloidogyne</i> species, does not confer significant residual effects against <i>M. enterolobii</i> (guava race).</p>

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Assessing the residual effects of the tomato Mi-1.2 gene against a Meloidogyne enterolobii (guava race) population via comparative assays with contrasting near-isogenic lines

  • 期刊论文

  • 发表日期：

    2025年7月10日

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  • Dwillian Firmiano Cunha,
  • Thávio Júnior Barbosa Pinto,
  • Maria Esther de Noronha Fonseca,
  • Giovani Olegário da Silva,
  • Felipe Santos Rafael,
  • Leandro Alves Santos,
  • Juvenil Enrique Cares,
  • Jadir Borges Pinheiro,
  • Leonardo Silva Boiteux

摘要

The interaction of the tomato Mi-1.2 gene with the members of the genus Meloidogyne is a special case where a single host factor confers resistance to an array of up to 13 species, but not against M. enterolobii populations. There are numerous reports of “defeated” resistance genes in distinct pathosystems, which are not effective against distinct pathogen variants (at biotype, race, or species level as in the case of the Mi-1.2 gene). However, a subgroup of these apparently non-effective genes can still display residual or “ghost” effects, resulting in lower damage levels caused by a virulent pathogen. Thus far, residual effects of the Mi-1.2 gene to M. enterolobii have not been properly investigated. Herein, two comparative assays using contrasting near-isogenic lines (NILs) for presence/absence of the Mi-1.2 locus were carried out using a guava race population of M. enterolobii. Seedlings of two pairs of contrasting NILs ‘Nemadoro’ (homozygous dominant; Mi-1.2/Mi-1.2) / ‘Rio Grande’ (homozygous recessive, mi-1.2/mi-1.2) and ‘Del Rey’ (Mi-1.2/Mi-1.2) / ‘Calipso’ (mi-1.2/mi-1.2) were inoculated with 2,000 M. enterolobii eggs. The homozygous dominant (Mi-1.2/Mi-1.2) NILs displayed values for the quantitative parameter number of eggs + J2s per gram of root tissue similar or even superior to their corresponding recessive (mi-1.2/mi-1.2) NILs. A slight positive impact of the resistance gene in the reproduction factor (RF) value was observed only for one pair of contrasting NILs (‘Del Rey’ / ‘Calipso’), which was restricted to one bioassay. Hence, the employment of NILs in our bioassays allowed us to hypothesize that the Mi-1.2 gene, although extremely effective against populations of at least 13 Meloidogyne species, does not confer significant residual effects against M. enterolobii (guava race).