Screening of Tomato Genotypes Against Root-Knot Nematode and Validation of Mi 1 Gene Linked Markers

Abstract

In India, tomato (Solanum lycopersicum L.) suffers yield loss between 11 and 35 % due to root-knot nematode (RKN) (Meloidogyne spp.) infestation. Mi 1 gene in tomato confers resistance to the three most damaging RKN species viz, Meloidogyne incognita, M. arenaria and M. javanica. The loss can be averted through the use of cultivars containing Mi 1 gene or incorporating the gene in new cultivars. To identify resistant genotypes, in 2013–2014 a total of 32 genotypes were screened against M. incognita at 2000 J2/Kg inoculum. Genotypes, Motelle and H-88-78-1 have showed immune reaction. Mogor and Hisar Lalit also showed resistance reaction. In 2014–2015, nine genotypes including four immune/resistant lines from the last year were screened against RKN at two inoculation rates of 2000 and 4000 J2. Reaction of Motelle was similar at both inoculum levels. In other resistant genotypes there was increase in mean of gall index when the inoculum levels were increased. The genetic background had an effect on the variations observed in number of galls produced in the resistant genotypes. Marker assisted selection for resistant genes greatly enhance selection of resistant plants in breeding. To identify suitable marker, six polymerase chain reaction based co-dominant markers were used for molecular screening of Mi 1 gene. Four markers namely, REX-1, CT119, Mi23 and Pmi gave banding pattern in accordance with the reported literature. Considering tight linkage with the gene and assay cost two sequences characterized amplified region markers, Mi23 and Pmi can be preferred over other markers for selecting Mi 1 containing genotypes.