Screening of eggplant genotypes for resistance to bacterial wilt disease caused by Clavibacter michiganensis subsp. michiganensis

Abstract

Clavibacter michiganensis subsp. michiganensis (Cmm) is one of the phytopathogenic bacteria causing bacterial wilt disease and severe yield losses in tomatoes and other solanaceous vegetables. Although there are some reports on Cmm infections in eggplants (Solanum melongena), there is no information available on the resistance sources and genetic control of the resistance to Cmm in this crop. We performed a search for resistance sources to Cmm in eggplants, in a set of 46 genotypes including landraces, inbred lines and cultivars and some cultivated and wild relatives, as well as an analysis of the genetic control of the resistance. A mixture of different Cmm strains from different genomic groups was used for the screening. Plants were inoculated through the injection of 10 µL of a Cmm suspension at a concentration of 10<sup>7</sup> cfu/mL in a single point of the stem. The symptoms were recorded at nine weeks after the inoculation with a 0–4 symptoms scale. The differences were observed in the symptoms in the collection evaluated, with the disease severity index of the genotypes ranging from 0.00 to 4.00. While 31 genotypes displayed no symptoms, three cultivated eggplant genotypes were highly susceptible. Reciprocal F1 and F2 generations were obtained from the crosses between the most susceptible genotype (CT30) and a resistant one (CT49). The genetic control of the resistance adjusted well to one dominant and one recessive gene model underlying the resistance to Cmm. These results are important for selection and breeding for resistance to Cmm in eggplants.