Nyoka tobacco plants with resistance to Meloidogyne javanica appeared sporadically in early selfed and hybrid progenies where resistance was tightly linked to undesirably small, narrow leaves, long internodes and profuse suckering. Differential linkage-breakage responses were obtained in different hybrid strains along with higher levels of resistance in S, and subsequent selfed generations. The alloploid N. sylvestris × N. tomentosiformis was the backcross parent most effective in breaking undesirable linkages and producing agronomically acceptable root-knot resistant flue-cured tobacco lines. After the linkages were broken, resistance appeared to be inherited in a monogenic dominant manner with one or more modifier genes enhancing the level of resistance. Root-knot resistance was a relative expression based on the degree of galling, and influenced by both genotypic and environmental agents.

(Full article published with kind permission from "Tobacco International")