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.

Immune recognition of the secreted serine protease ChpG restricts the host range of Clavibacter michiganensis from eggplant varieties

“…The host range of Cm is mostly restricted to tomato and pepper; the bacteria cannot cause disease in potato and in numerous varieties of eggplant (Boyaci et al, 2021 ; Yim et al, 2012 ). We speculated that immune recognition plays a role in determining the host range of Cm.…”

“…A recent screen conducted by Boyaci and colleagues identified that numerous eggplant varieties demonstrate moderate to high Cm resistance and classified only three out of 46 screened varieties as susceptible to the bacteria (Boyaci et al, 2021 ). We hypothesized that resistance to Cm, which is abundant in eggplants, is mediated through immune recognition of ChpG.…”

“…Eggplant genes associated with immunity to Cm are yet to be identified. A recent screen identified that a large number of eggplant varieties are resistant to Cm and that this resistance is likely to be associated with a single dominant locus (Boyaci et al, 2021).…”

“…However, backcross attempts into domesticated tomatoes only conferred partial resistance to the pathogen (Coaker & Francis, 2004; van Heusden et al, 1999). A recent study aimed at characterizing eggplant ( Solanum melongena ) susceptibility to Cm identified that numerous eggplant varieties demonstrate moderate to high resistance to Cm (Boyaci et al, 2021). In addition, reciprocal crosses between susceptible and resistant varieties followed by segregation analyses identified that resistance to Cm is a dominant trait that follows Mendelian‐like segregation, indicating that eggplant resistance to Cm is likely to be linked to a single locus (Boyaci et al, 2021).…”

Comparative Analysis of the NDVI and NGBVI as Indicators of the Protective Effect of Beneficial Bacteria in Conditions of Biotic Stress

“…The pathogen can be spread by seed and agronomic practices [ 17 ]. The usage of biocontrol agents and resistant cultivars might be alternative solutions to control the pathogen, but these methods have not yet been implemented in the field [ 18 ]. There is evidence that plant signaling pathways regulating the development of protective responses to stresses are the key targets of PGPB [ 19 ].…”