72 Indian Journal of Agricultural Sciences 89 (6): 964–8, June 2019/Article Validation of molecular markers for multiple disease resistance in tomato (Solanum lycopersicum) ZAKIR HUSSAIN 1 , SUMAN LATA 2 , MANISHA MANGAL 3 , B S TOMAR 4 , R K YADAV 5 , GOKUL GOSAVI 6 , ASHWANI KUMAR 7 , PAWAN YADAV 8 , MONIKA 9 and S K YADAV 10 ICAR-Indian Agricultural Research Institute, Pusa Campus, New Delhi 110 012, India Received: 6 September 2018; Accepted: 31 December 2018 ABSTRACT Marker assisted breeding has been successfully used for selecting disease resistance by identifying genetic markers linked to resistance genes/allele. In tomato, availability of molecular markers linked to genes conferring resilience against Tomato leaf curl virus (ToLCV) reaction, late blight, Tomato Mosaic Virus (ToMV) and Tomato gray leaf spot were utilised to develop pyramided MAS derived lines for multiple disease resistance. For this purpose, markers for the tomato leaf curl disease (ToLCD) resistance gene loci Ty-2, Ty-3 and Ty-3a, late blight resistant loci Ph-3, ToMV resistant allele Tm2 2 and Tomato gray leaf spot resistant gene Sm were validated using PCR assay. The assay correctly predicted the genotypes of tomato breeding lines harbouring resistant as well as susceptible alleles at each loci. Duplexing PCR assay combining two SCAR markers (T0302 and P6-25) for detecting simultaneously 3 important resistance gene loci (Ty-2, Ty-3 and Ty-3a) in tomato genotypes and thereby improving the cost effciency of the PCR assay. Further, we have validated the Tomato leaf curl New Delhi virus (ToLCNDV) infection in tomato leaves by Reverse transcription (RT) PCR with ToLCNDV genome specifc AC4 primers. Key words: Late blight, Marker-assisted selection (MAS), Tomato, Tomato gray leafspot, Tomato leaf curl virus (ToLCV), Tomato Mosaic Virus (ToMV) Present address: 1,3,4,5 Principal scientist (drzakirhussain24@ gmail. com, manishamangal@iari. res. in, bst_spu_iari@rediffmail. com, rkyadavneh@gmail. com); 2 Scientist (sumanlata3@gmail. com), 6,7,8,9 SRF (gosavi. gokul@gmail. com, ashwinikumar1500@ gmail. com, pawanyadav0626@gmail. com, ICAR-IARI; 10 (satish. yadav1@icar. gov. in), ICAR-NBPGR. Tomato production is often threatened due to severe losses caused by various pathogens including viruses, bacteria, fungi, and nematodes. Molecular breeding using molecular markers are now being widely used in tomato (Foolad and Sharma 2004). There are more than 40 genes that confer resistance to major classes of tomato pathogens which can be pyramided through MAS, for the introgression of more than one resistance genes into 1 genotype. In India, tomato leaf curl disease (ToLCD) is one of the most devastating diseases of tomato. Symptoms of ToLCD include stunting, yellowing, leaf curling and fower abortion which results in signifcant yield loss (Chakraborty et al. 2009). Most of tomato cultivars in India are susceptible to ToLCD. However, several wild species of tomato including Solanum chilense, Solanum habrochaites and Solanum peruvianum (Ji et al. 2007a) have been found promising for ToLCD resistance. Currently, 6 resistance genes i. e. Ty-1and Ty-3 on chromosome 6, Ty-2 on chromosome 11, Ty-4 on chromosome 3, ty-5 on chromosome 4 and Ty-6 on chromosome 10 are available for commercial breeding against ToLCD (Zamir et al. 1994, Ji et al. 2007b). Ty- 1and Ty-3 were demonstrated to be allelic (Verlaan et al. 2013). Ty-2 originated from S. habrochaites B6013 (Ji et al. 2009a) mapped to a 300 kb interval on chromosome 11 (Yang et al. 2014). Ty-4 (Ji et al. 2009b) and Ty-6 (Hutton and Scott 2013) have also originated from S. chilense accessions. Recessive resistance against TYLCV was identifed in S. peruvianum and designated as ty-5 (Hutton et al. 2012). The Ph-3 gene with a coiled-coil nucleotide-binding leucine-rich repeat (NBS–LRR), conferring incomplete resistance against a wide range of Phytophthora infestans isolates has been introgressed into cultivated tomatoes from S. pimpinellifolium (L3708) (Zhang et al. 2014). Tomato Mosaic Virus (ToMV) disease is another important disease of tomato which causes signifcant yield losses. Based on molecular studies the Tm2 2 allele derived from Solanum chilense has proved most effcient in providing resistance against ToMV (Lanfermeijer et al. 2003). Tomato gray leaf spot is another devastating disease of tomato caused by Stemphylium lycopersici. The Sm gene has incomplete dominance and considered as effective source of resistance against 4 species of Stemphyllium (Scott and Gardner 2006). https://doi.org/10.56093/ijas.v89i6.90770