Transcriptome analysis during ToLCBaV disease development in contrasting tomato genotypes.

Tomato leaf curl Bangalore virus (ToLCBaV) is one of the most important plant viruses. The infection causes substantial yield losses in tomato crop. The current viral disease management is based mainly on introgression of Ty locus into new tomato cultivars. Unfortunately, strains of the leaf curl virus have been evolving and are breaking Ty based tolerance in tomato. In this study, the defence response to ToLCBaV infection has been compared between contrasting tomato genotypes, resistant line (IIHR 2611; without any known Ty markers) and the susceptible line (IIHR 2843). We carried out comparative transcriptome profiling, and gene expression analysis in an effort to identify gene networks that are associated with a novel ToLCBaV resistance. A total of 22,320 genes were examined to identify differentially expressed genes (DEGs). We found that 329 genes of them were expressed significantly and differentially between ToLBaV-infected samples of both IIHR 2611 and IIHR 2843. A good number of DEGs were related to defence response, photosynthesis, response to wounding, toxin catabolic process, glutathione metabolic process, regulation of transcription DNA-template, transcription factor activity, and sequence-specific DNA binding. A few selected genes such as, nudix hydrolase 8, MIK 2-like, RING-H2 finger protein ATL2-like, MAPKKK 18-like, EDR-2, SAG 21 wound-induced basic protein, GRXC6 and P4 were validated using qPCR. The pattern of gene expression was significantly different in resistant and susceptible plants during disease progression. Both positive and negative regulators of virus resistance were found in the present study. These findings will facilitate breeding and genetic engineering efforts to incorporate novel sources of ToLCBaV resistance in tomatoes. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03629-5.

Differential expression of carotenoid biosynthetic pathway genes in two contrasting tomato genotypes for lycopene content.

Tomato (Solanum lycopersicum L.) is one of the model plant to study carotenoid biosynthesis. In the present study, the fruit carotenoid content were quantified at different developmental stages for two contrasting genotypes, viz. IIHR-249-1 and IIHR-2866 by UPLC. Lycopene content was high in IIHR-249-1 (19.45 mg/100 g fresh weight) compared to IIHR-2866 (1.88 mg/100 g fresh weight) at the ripe stage. qPCR was performed for genes that are involved in the carotenoid biosynthetic pathway to study the difference in lycopene content in fruits of both the genotypes. The expression of Phytoene synthase (PSY) increased by 36-fold and Phytoene desaturase (PDS) increased by 14-fold from immature green stage to ripe stage in IIHR-249-1. The expression of Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta cyclase (CYC-B) decreased gradually from the initial stage to the ripe stage in IIHR-249-1. IIHR 249-1 showed 3- and 1.8-fold decrease in gene expression for Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta-cyclase (CYC-B) .The F2 hybrids derived from IIHR-249-1 and IIHR-2866 were analysed at the ripe stage for lycopene content. The gene expression of Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta-cyclase (CYC-B) in high and low lycopene lines from F2 progenies also showed the decrease in transcript levels of both the genes in high lycopene F2 lines. We wish to suggest that the differential expression of lycopene beta-cyclases can be used in marker-assisted breeding.

Genotypic variability for antioxidant and quality parameters among tomato cultivars, hybrids, cherry tomatoes and wild species.

BACKGROUND: Wide germplasm diversity and transferability of antioxidant parameters is the primary requirement for the development of high-antioxidant tomato cultivars. The present study was conducted to screen tomato genotypes including hybrids, varieties, cherry tomatoes, wild species, elite germplasm lines, interspecific hybrids and backcross populations for antioxidant activity and other quality parameters to select high-antioxidant lines with good total soluble solids (TSS) for further usage in crop improvement programmes. RESULTS: Wild species and interspecific hybrids between LA-1777 (Solanum habrochaites) and an elite genotype 15SBSB recorded very high antioxidant capacity (FRAP), DPPH radical-scavenging ability, and high phenols and flavonoids. Interspecific hybrids also recorded very high total soluble solids (TSS). Significantly higher total carotenoids, lycopene and vitamin C were observed in IIHR-249-1 with moderately higher TSS. Cherry tomato lines IIHR-2866, 2865 and 2864 recorded four to five times more ß-carotene than commercial hybrids/varieties. CONCLUSION: Tomato line IIHR-249-1 can be used for improving antioxidant capacity, total carotenoids and lycopene in tomato breeding programmes. Cherry tomato lines IIHR-2866, 2865 and 2864 can be used for improving ß-carotene content. LA-1777 and interspecific hybrids could be used for developing tomato lines rich in antioxidants as well as TSS.