North Carolina’s robust tobacco industry faces a new threat from Meloidogyne enterolobii, the guava root-knot nematode, which was first identified in the state in 2011. This species can overcome host resistance in tobacco that is effective in managing other root-knot nematode (RKN) species such as M. incognita. Novel sources of host resistance are therefore needed for this pathogen. This study evaluated potential tobacco host resistance to M. enterolobii through a series of greenhouse bioassays. Genotypes of Nicotiana tabacum and other Nicotiana species (n=84) were assayed for response to M. enterolobii. Materials were selected to represent commercially important cultivars, resistance to other RKN species, resistance to other plant-parasitic nematodes and pathogens, genetic diversity, and those carrying introgressed chromosomal segments from wild Nicotiana relatives. Plants were inoculated with 10,000 eggs per plant of a North Carolina isolate of M. enterolobii and eggs from resultant infections were extracted 60 days post inoculation. Data were collected for eggs per gram of root and root galling severity. Resistance and susceptibility were quantified by calculating each line’s reproductive factor (RF, final population/initial population). All materials were assessed for response through two independent bioassay trials, and genotypes displaying resistance were subsequently retested in replicates of ten in a confirmation screening. Six genotypes of wild Nicotiana species were found to be either highly resistant or moderately resistant to M. enterolobii. These lines may offer useful germplasm for future resistance breeding efforts and further characterization of resistance in Nicotiana to M. enterolobii.
Bonyak et al. (Sun,) studied this question.