Marker assisted early generation identification of root knot disease resistant orange tomato segregants with multiple desirable alleles.

Enhanced bioavailability of cis-isomers of lycopene, accumulated in orange-fruited tangerine mutant has broadened the scope of nutritional enrichment in tomato. At the same time, advancements in the field of marker assisted selection (MAS) have made the stacking of multiple desirable alleles through molecular breeding to develop superior tomato genotypes possible. Here we report seedling stage MAS from 146 F2 plants, to identify 3 superior performing, root knot disease resistant orange-fruited segregants. In the selected segregants, fruit weight ranged from 39.2 to 54.6 g, pericarp thickness ranged from 4.56 to 6.05 mm and total soluble solid content ranged from 3.65 to 4.87° Brix. Presence of parental diversity allowed identification of the other desirable alleles of the genes governing late blight and mosaic disease resistance, growth habit (determinate and indeterminate) as well as fruit elongation and firmness. Resistance to root knot disease of the selected 3 segregants was also validated through a unique method employing in vitro rooted stem cuttings subjected to artificial inoculation, where the resistant parent and the selected segregants developed no galls in comparison to ~ 24 galls developed in the susceptible parent. The selected segregants form the base for development of multiple disease resistant, nutritionally enriched orange-fruited determinate/indeterminate tomato lines with superior fruit quality. The study also highlights the utility of early generation MAS for detailed characterization of segregants, through which multiple desirable alleles can be precisely targeted and fixed to develop superior tomato genotypes. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01361-1.

Rapid genotyping in tomato by VPCR using agarose gel-resolvable InDel markers.

Insertion/deletion (InDel) markers are second most abundant polymerase chain reaction (PCR)-based molecular markers having enormous applications in genotyping and molecular breeding in different crops. Although standard polymerase chain reaction (PCR) for DNA amplification generally takes ~ 1.5 to 2 h, small amplicons can be effectively generated using dynamic heating and cooling through PCR with "V"-shaped thermal profile (VPCR) in ~ 15 to 20 min. Here, we evaluated the applicability of a partly modified VPCR method for amplifying InDels of tomato genome. Out of the 31 InDel markers tested in 15 diverse tomato genotypes, 29 markers resulted in sharp amplicons, where 26 markers were found to be polymorphic. Using this method, the individual DNA amplification reactions could be completed within ~ 30 min. The method was effective for primers varying in melting temperature (T m) and GC contents. Furthermore, the need for empirically determining suitable annealing temperature could be bypassed using this generalised thermal profile. Through our results, we advocate the use of this method of DNA amplification in other plants to achieve rapid genotyping using standard molecular biology equipments and procedures. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03499-x.

Marker assisted stacking of Ty3, Mi1.2 and Ph3 resistance alleles for leaf curl, root knot and late blight diseases in tomato.

Developing multiple disease resistance through naturally available host resistance alleles is a challenging as well as rewarding area of research. Availability of host resistance alleles and the reliability of their identification through diagnostic molecular markers have paved the way for stacking of these resistance alleles for developing important genetic resources in tomato. Here we report the marker assisted stacking of Ty3, Mi1.2 and Ph3 alleles, governing leaf curl, root knot and late blight disease resistance, respectively, in superior F4 segregants of tomato derived from two diverse parents (i.e., BRDT-1 and H-88-78-1). Marker assisted selection was applied only on morphologically superior segregants at F2 and F3 generations, which helped us in identifying suitable lines even from a relatively small population. The diagnostic values of the employed molecular markers advocate that the identified superior segregants, carrying all the three aforementioned resistance alleles in homozygous condition, are suitable to be explored as valuable genetic resources for developing multiple disease resistance through rapid introgression of these genes in different genetic background of tomato. Identification of suitable segregants derived from these lines should be promising for obtaining improved cultivars in near future. Nevertheless, these lines might be further explored to decipher the intrinsic details of host's resistance mechanism involving genetic interactions between different resistance factors. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01277-2.