ISHS Acta Horticulturae 695: I International Symposium on Tomato Diseases
PCR-BASED METHODS FOR TAGGING THE MI-1 LOCUS FOR RESISTANCE TO ROOT-KNOT NEMATODE IN BEGOMOVIRUS-RESISTANT TOMATO GERMPLASM |
| Authors: | K. El Mehrach, S. Gharsallah Chouchane, L. Mejia, V.M. Williamson, F. Vidavski, A. Hatimi, M.S. Salus, C.T. Martin, D.P. Maxwell |
| Keywords: | Lycopersicon esculentum, Meloidogyne species, Mi-1 locus, REX-1 locus, Mi-1.2 gene, polymerase chain reaction |
| Abstract:
The begomovirus-resistant breeding lines being developed in Guatemala were tested for the CAPS markers, REX-1 and Cor-Mi, that are linked to the Mi-1 locus for root-knot nematode resistance. Both markers gave false positive results for several breeding lines that are susceptible to M. incognita and have L. hirsutum (line Ih902) or L. chilense (line TY52) introgressions. SNPs and indels specific to introgressions from two wild species, L. peruvianum and L. chilense, are described for the two CAPS markers. A multiplex PCR was developed, which involved the REX primers and PCR primers (PM3Fb/PM3Rb) specific for the region 3’ of the Mi-1.2 gene. Every plant DNA tested gave a 720-bp fragment for the REX primers, but only those plants with the Mi-1.2 gene gave a 500-bp fragment with the PM3Fb/PM3Rb primers. Since this multiplex PCR could not detect heterozygous genotypes for the Mi-1.2 gene, another PCR method was used with primers (PMiF3/PMiR3), which gave unique fragment sizes for the Le-Mi-1 locus, the Lp-Mi-1 locus and the Lc-Mi-1 locus, as well as with the begomovirus-resistant line with the Ih902-Mi-1-locus. These two PCR protocols will have application in breeding programs in which parental lines have given false positives with the REX-1 and Cor-Mi markers, i.e., especially those using parental lines with begomovirus-resistance genes introgressed into chromosome 6S. | |
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