Screening of Tomato (Solanum lycopersicum L.) Germplasm for Root-Knot Nematode Resistance using Conventional and Molecular Marker Techniques

Two hundred tomato germplasm lines were screened following conventional (sick plot and artificial inoculations in pots) and molecular marker techniques to identify resistant sources. PNR-7 and Punjab Upma were used as resistant and susceptible checks, respectively. Seven lines viz. Hisar Lal, EC631955, EC631956, EC631957, EC119197, 8-2-1-2-5 and 1-6-1-4 were found to possess high degree of resistance and two lines viz. EC 531804 and PAU Acc.-1 were found resistant through conventional screening. The resistant lines along with some hybrid combinations involving resistant x susceptible parents were then screened using SCAR marker Mi23, linked to the RKN resistant gene Mi-1. The lines Hisar Lal, EC631955, EC631956, EC631957, EC119197, EC531804, PAU Acc-1, 8-2-1-2-5 and 1-6-1-4 amplified the expected product size of ∼380bp linked to the Mi locus conferring resistance to RKN. Punjab Upma, the susceptible check along with two susceptible test lines generated the ∼420bp band showing absence of Mi locus. The hybrids 8-2-1-2-5 x Punjab Upma, Hisar Lal x Punjab Upma, EC119197x Punjab Upma and Hisar Lal x CR2P-8-6 generated both the bands and were, therefore, heterozygous for the resistant locus (Mi-1/mi-1).