Phenotypical and molecular characterization of new pepper genotypes resistant to Chili pepper mild mottle virus firstly detected in Europe and other tobamoviruses

Abstract

The tobamoviruses pose a recent threat to local varieties of Gernika pepper (cv. “Derio”) and Ibarra chili (cv. “Ibarroria”), causing a substantial decrease in both yield and fruit quality. Tobamoviruses such as Tomato mosaic virus (ToMV), Tobacco mild green mosaic virus (TMGMV) or Pepper mild mottle virus (PMMoV) are the viruses that cause the greatest impact in pepper crops of northern Spain. The emergence of a novel Tobamovirus, Chili pepper mild mottle virus (CPMMoV; GenBank MN164455.1), firstly identified in Europe, exacerbates these hazards. This situation has jeopardized the ongoing cultivation in some of the virus affected plots. A molecular marker-assisted backcrossing (MABC) breeding program was thus initiated to introduce the L3 and L4 resistance genes into these susceptible local varieties. MABC consisted of one crossing followed by four backcrosses and two self-fertilizations. After each crossbreeding event, the selection criteria of plants were based on plants resistance and fruits resemblance with the original sensitive varieties. This study allowed the homozygous introgression of resistance genes in the new obtained genotypes, reducing the reliance on hybrid seed production and associated costs. The resulting genotypes demonstrated robust resistance when inoculated with PMMoV 1.2, PMMoV 1.2.3, and CPMMoV. In addition, greenhouse yield trials were performed during two consecutive years to identify and select the most productive genotypes harboring the L3 or L4 gene, with the aim of registering some of them as commercial varieties. The productivity of the new selected genotypes did not display significant differences when compared to the original sensitive varieties. The introduction of genetic resistance in these local pepper varieties not only mitigates the immediate hazard posed by Tobamovirus but also fosters the preservation of local agricultural genetic resources, ensuring their continued cultivation and economic sustainability.