A Single Recessive Gene for Resistance to the Root-Knot Nematode (Meloidogyne Javanica) in Cucumis sativus var. hardwlckii

Resistance to the root-knot nematode (Meloidogyne javanica) was identified in the Cucumis sativus var. hardwickii line LJ 90430. Parents, F1 F2 and BC1 to both parents of a cross between Sumter (Cucumis sativus var. sativus) and LJ 90430 were evaluated in two greenhouse experiments to determine genetics of resistance to M. javanica. All F1 progeny were susceptible, and segregation ratios in the F resulted in 1 resistant:3 susceptible. Backcross progeny to the susceptible parent were susceptible, and the BC1 to the resistant parent segregated 1 resistant:1 susceptible. Reciprocal crosses did not differ and therefore showed no evidence of maternal or cytoplasmic effects. Results from the crosses of several inbreds (Addis, Gy 14, Gy 57u, Poinsett 87, and Sumter) with LJ 90430 indicated that use of those five different genetic backgrounds had no influence on gene expression. The five F2 families segregated in a 1 resistant: 3 susceptible ratio. The five BC, (to LJ 90430) families segregated in a 1 resistant:1 susceptible ratio. F3 families were developed from resistant and susceptible F2 plants using the five inbreds. Resistant F2:3 families produced progeny that were all resistant, and susceptible F2:3 families fit a ratio of 1 susceptible:2 segregating. Thus, resistance to M. javanica is conferred by a single recessive gene for which we propose the symbol mj.